biology activities for gcse - National STEM Centre

BIOLOGY
ACTIVITIES FOR GCSE
GCSE
courses from
1996
Nuffield

Nuffield Science Activities for GCSE
General editor
Mary Whitehouse
Biology editor
Diane Galloway
Biology contributors
Andrew Hunt
John Kearsey
Jean McLean
Grace Monger
Alastair Sandiforth
Paul Spencer
Tim Turvey
Biology safety adviser
Philip Bunyan
Published by the Nuffield Foundation, 28 Bedford Square, London WC1B 3EG
© Nuffield Foundation 1996
Illustrations by Hugh Neill and Oxford Illustrators
We are grateful to Addison Wesley Longman for permission to reproduce many of the drawings in this book.
Printed in Great Britain by Printfast, Rathbone Place, London Wl
This work is copyright, but copies may be made without fee or prior permission provided that the work has been paid for and
such copies are used solely within the institution for which the work is purchased. Works sent on approval or inspection and
not yet paid for may not under any circumstances be copied. For copying in any other circumstances (e.g. by an external
resource centre), prior written permission must be obtained from the Publishers and a fee may be payable.
The Foundation has made every effort to contact copyright holders of illustrations and extracts appearing in this book. In any
instance where it has been unsuccessful it invites the copyright owner to contact it directly.
ISBN 0 904956 28 8

BIOLOGY
ACTIVITIES FOR GCSE
Teachers' notes
Muffield

Jl____________________________________________
Nuffield Science Activities for GCSE
General editor
Mary Whitehouse
Biology editor
Diane Galloway
Biology contributors
Andrew Hunt
John Kearsey
Jean McLean
Grace Monger
Alastair Sandiforth
Paul Spencer
Tim Turvey
Biology safety adviser
Philip Bunyan
Published by the Nuffield Foundation, 28 Bedford Square, London WC1B 3EG
© Nuffield Foundation 1996
Illustrations by Hugh Neill and Oxford Illustrators
We are grateful to Addison Wesley Longman for permission to reproduce many of the
drawings in this book.
Printed in Great Britain by Printfast, Rathbone Place, London Wl
This work is copyright, but copies may be made without fee or prior permission provided
that the work has been paid for and such copies are used solely within the institution for
which the work is purchased. Works sent on approval or inspection and not yet paid for
may not under any circumstances be copied. For copying in any other circumstances (e.g.
by an external resource centre), prior written permission must be obtained from the
Publishers and a fee may be payable.
Acknowledgements
Page 34: drawing based on Roberts, MBV Biology for life Nelson, 2nd edn 1986
Page 36: drawing based on Mackean, DG GCSE Biology John Murray, 1986
Page 63: cartoon by Paul Boyes
Page 83: drawings based on photomicrographs in McLeish, J. and Snoad, B. Looking at
chromosomes Macmillan, 1958
Page 120: map from Patterson, KD and Pyle, GF 'The geography and mortality of the 1918
influenza pandemic' Bulletin of the history of medicine 65 (1) 4-21, spring 1991.
Activity B33 contains extracts, reproduced with permission, from University of London
Examinations and Assessment Council GCSE Biology examination paper
The Foundation has made every effort to contact copyright holders of illustrations and
extracts appearing in this book. In any instance where it has been unsuccessful it invites the
copyright owner to contact it directly.
ISBN 0 904956 28 8

Ill
Contents
Introduction page 1
Section B1 Life processes: an overview page 7
Section B2 Levels of organization paged
Bl Skill sheet - Using a microscope 8
B2 Cells and what they do 9
B3 Body systems in Daphnia 10
B4 Body systems in animals 11
Section B3 Nutrition in plants and animals page 12
B5 How do gases get in and out of leaves? 12
B6 Photosynthesis 12
B7 Skill sheet - Testing for starch 13
B8 Plants we eat 14
B9 Do plants and animals alter the environment around them? 17
B10 What affects the rate of photosynthesis? 18
Bll Factors affecting photosynthesis 19
B12 The food tube 20
B13 The food tube (diagrams showing structure and function) 20
B14 The food tube (diagrams showing microscopic structure and digestion of molecules) 20
B15 Enzymes and digestion 21
B16 More about digestive enzymes 23
B17 The value of villi 25
B18 Foods and food tests 26
Section B4 Transport in plants and animals page 28
B19 Looking at the heart 28
B20 What does the heart do? 29
B21 What happens if you have a heart attack? 29
B22 Blood and blood transfusions 31
B23 Looking at diffusion 33
B24 Water in and out of cells 34
B25 Osmosis and turgor 35
B26 Active transport 36
B27 A summary of mass flow, diffusion, osmosis and active transport 37
B28 Minerals for plant growth 37
B29 Measuring the rate of water loss from leaves 39
B30 Water from roots through leaves 40
Section B5 Respiration page 42
B31 Where does air go when you breathe in? 42
B32 How you inflate your lungs 43
B33 Understanding asthma 45
B34 Investigating respiration 46
B35 How much energy is there in some foods that you eat? 46
B36 Investigating cigarette smoke and its effects 48
B37 Smoking 49
Section B6 Energy and nutrient transfer page 50
B38 Energy flows 50
B39 Food chains and food webs 50
B40 Building pyramids of numbers 51
B41 Building pyramids of biomass 53
B42 Pesticides in food chains 54
B43 The carbon cycle 55
B44 The nitrogen cycle 57
B45 The nitrogen cycle game 58

IV
Section B7
Health
B46 Body defences
B47 How does a theory become an accepted fact?
B48 Germs and you
B49 Alcohol
Section B8
The nervous system and hormones
B50 Stimulus and response
B5 1 Nerves or glands?
B52 Hormones to control blood glucose
B53 Hormones and cycles
B54 Tropisms in shoots
B55 Tropisms and plant hormones
B56 Rights and wrongs of using hormones
Section B9
B57
B58
Homeostasis
Keeping a steady state
What does dialysis do to blood?
Section B10 Cell division
B59 A model of mitosis
B60 Cells dividing
B61 A flick book to show mitosis
B62 DNA, genes and protein synthesis
B63 Chromosones in sex cells
Section B11
Variation
B64 Variation in people
B65 Variation in ivy leaves
B66 Generations of tomato plants
B67 Making an identification key
Section B12 Inheritance
B68 Breeding with beads
B69 Skipping a generation
B70 Sex-linked inheritance
B71 Two inherited diseases
B72 Genes
B73 Genetic engineering
B74 Genetic engineering - the issues
B75 Cloning a cauliflower
B76 Plant and animal clones
B77 Selective breeding
B78 Potato cyst eelworm and potato blight
Section B13 Evolution
B79 Fossils
B80 A theory based on natural selection
B81 How many offspring?
B82 Darwin's century
B83 Selection in action
B84 Using models to explain selection
B85 New types of flu
page 59
59
60
60
64
page 66
66
69
70
71
73
73
75
page 76
76
78
page 81
81
82
84
84
85
page 88
88
90
91
92
page 95
95
95
97
99
100
101
103
104
106
108
109
page 112
112
113
114
116
118
119
119

Section B14 The impact of human activities page 122
B86 Patterns in the distribution of a simple plant 123
B87 Investigating plant populations 124
B88 Red squirrels 125
B89 Types of pollution 126
B90 Monitoring water pollution 127
B91 Nitrates in water 129
B92 Acid in the air 131
B93 How do pollutants affect Chlorellal 132
B94 Global warming 133
B95 In defence of modern farming 134
B96 Plant protection in Thailand 135
Further information page 138
Further information about plant nutrition 138
Further information about food and digestion 138
Further information about human physiology 138
Further information about carbon and nitrogen cycles 139
Further information about health 140
Further information about cancer 140
Further information about nerves and hormones 140
Further information about reproduction 141
Further information about inheritance 141
Further information about evolution 142
Further information about ecology 142
Further information about pollution 143
Addresses 144

Nuffield Biology
Introduction
This pack of activity sheets is designed to match the National Curriculum Science: Biology
at Key stage 4. The ideas are drawn from materials produced by various Nuffield projects
over the past ten years. The editors acknowledge the work of the many teachers and writers
involved in those projects.
Activities
The pack contains activities which exemplify the Nuffield approach to learning science.
Many of the activities require apparatus and laboratory facilities. Others lend themselves to
group discussion or private study at school or at home.
National Curriculum links
GCSE syllabuses
These activity sheets were developed to match the syllabus jointly developed by MEG and
Nuffield. They are cross referenced in the MEG teacher support booklets published by MEG
for the Co-ordinated Science double and single award syllabuses (1794 and 1795). They are
also referred to in the Science: Biology (Nuffield) syllabus (1785).
The nature of science
The introduction to the Programme of Study provides an over-arching philosophy which
should pervade the whole science course. This part of the National Curriculum, which
precedes Scl, is becoming known as ScO and we have adopted this convenient label in these
notes. The ideas are
1 Systematic enquiry,
2 Application of science,
3 The nature of scientific ideas,
4 Communication,
5 Health and safety.
Many activities in this pack cover these ideas within the context of biology. The notes
for each activity indicate which particular aspects of ScO are touched on.
Many of the activities provide opportunities for students to develop their investigative
skills and at the same time gain experience in the ways in which scientists carry out
systematic enquiries.
Students learn much by talking about science in small groups or to the class as a
whole. Putting their ideas into words helps them to clarify their understanding of scientific
principles. There are activities which involve structured discussion in small groups and
encourage reporting back orally both to a small group and to the whole class.
Writing about science also helps students to develop their understanding of a topic.
Several activities encourage students to put words and pictures together to produce their
own science descriptions and explanations.
There are also many activities in which they have to interpret or record information in
various forms, including tables, charts, graphs, diagrams, and models. Gathering,
displaying and interpreting data are an important feature of these activities. Students work
with data from secondary sources in various forms.

2 Biology Introduction
Opportunities for co-ordination
Biology, Chemistry and Physics do not stand in isolation from each other. There are many
occasions where the topic studied in one subject links with work carried out in one of the
other sciences. Where separate teachers are teaching the three subjects they may not be
aware of these links. The notes for each activity indicate where these links occur. This will
provide opportunities for teachers to highlight the links with their students.
Differentiation
There are two tiers of learning and assessment within the GCSE syllabuses - Foundation
Tier and Higher Tier. Activities directed at the Higher Tier learning outcomes are indicated
by H in the activity title in these Teachers' notes. Activities are only classified as H if
they exclusively cover higher tier learning outcomes.
All the text of the activities is supplied on disc. This will enable teachers to edit
activity sheets where necessary to meet the needs of the students in their class.
Teaching strategies
We have tried to bring variety and diversity to:
the ways in which the activities are presented (ways in),
the nature of the activities themselves (on task),
how the outcomes are communicated (ways out).
In a Key stage 4 science course, we expect our students to work through a large number of
separate tasks in school and for homework. Puzzling out what they have to do can become
a big part of the challenge for students. This is a particular problem for those who have
reading difficulties in a programme presented on worksheets. It is not the task itself which
is the stumbling block, but the impenetrable way in.
Just because we have described the activities on worksheets does not mean the students
have to get into the task that way. Some teachers choose to read the instructions on to an
audio tape which their students can then listen to on a personal stereo. Others like to start
activities with teacher talk and demonstration so that the activity sheet is there as a helpful
reminder rather than as the only way in.
Of course, the tasks themselves do vary in difficulty and complexity. Strategies we
have used to introduce differentiation into the programme include:
alternative activities,
activities designed to allow success at different levels and/or with differing
degrees of assistance from the teacher,
more demanding items towards the end of an activity or section.
Writing and record keeping can spoil the science for those who find it burdensome. Yet
we think that students can learn more from producing their own account of a topic in words
and pictures than they can from looking at someone else's account in a textbook.
Encouraging students to put ideas together is a crucial part of our strategy for
differentiation. We have tried, where possible, to include helpful drawings, captions and
diagrams for the students to give them help and encouragement with their written work.
Some, of course, need much help.
Safety
Safety in school science affects all concerned: teachers and technicians, their employers,
school students, their parents or guardians, authors and publishers.
As part of the reviewing process, these activities have been checked for safety. In
particular, we have attempted to ensure that:
all recognized hazards have been identified (both those covered by the COSHH
Regulations and the Management of Health and Safety at Work Regulations),
suitable precautions are suggested,

Biology Introduction 3
where possible, the procedures are in accordance with commonly adopted general risk
assessments,
where general risk assessments are not available, procedures are judged to be
satisfactory and of an equivalent standard.
It is assumed that:
practical work is conducted in a properly equipped and maintained laboratory,
rules for student behaviour are strictly enforced,
fieldwork takes account of any guidelines issued by the employer,
mains-operated equipment is regularly inspected and properly maintained, and
appropriate records are kept,
care is taken with normal laboratory operations such as heating substances and
handling heavy objects,
good laboratory practice is observed when chemicals, living organisms and materials of
living origin are handled,
eye protection is worn whenever there is any recognized risk to the eyes (including
activities involving heating substances, those involving toxic, corrosive or flammable
chemicals or those where heat may be generated in a chemical reaction),
any fume cupboard required operates at least to the standard of the DES Architects and
Building Group Design Note 29, Fume cupboards in schools, HMSO, 1982 (under
revision, 1996),
pupils are taught safe techniques for activities such as heating chemicals, smelling
them, pouring from bottles or handling micro-organisms,
hand-washing facilities are available in the laboratory.
Employers are obliged to carry out risk assessments before hazardous chemicals are used or
made, harmful micro-organisms are used, or before any hazardous procedure is carried out.
Mostly, they will do this by adopting general risk assessments (see below). Although every
care has been taken in producing this publication, teachers should still check that what is
suggested is in accordance with their employer's requirements, and consider whether any
modification is needed because of the particular circumstances of their school or class. Your
employers will be either the local education authority or the board of governors of your
school, which will be stated in your terms of contract.
Any local rules issued by the employer must always be followed, whatever is
recommended here.
General risk assessments have been taken from, or are compatible with:
Topics in safety, 2nd edition, Association for Science Education, 1988.
CLEAPSS Hazcards 1995, Consortium of Local Education Authorities for the
Provision of Science Services (only available to members) and the CLEAPSS
'Laboratory handbook' (1988 and later supplements).
Microbiology: an HMI guide for schools and further education, DES, HMSO, 1990.
You may also find it helpful to have these publications for reference:
Safeguards in the school laboratory, tenth edition, Association for Science Education,
1996.
Hazardous chemicals: a manual for schools and colleges, SSERC, Oliver and Boyd,
1979, new edition in preparation 1996.
Safety in science education, DfEE, 1996
Safety reprints, ASE, 1996.
Clearly, you must follow whatever procedures for risk assessment your employers have laid
down. As far as we know, all the practical work and demonstrations in this module are
covered by the general risk assessments detailed in the above publications, and so in most
schools you will not need to take further action.
If you decide to try some procedure with hazardous substances beyond what is in this
course, and you cannot find it in these or other General Assessments, your employer will
have to make a special risk assessment.
Only you can know when your school needs a special risk assessment. But thereafter,
the responsibility for taking all the steps demanded by the regulations lies with your
employer. If your employer is a member, CLEAPSS will act for them. Otherwise the ASE
may be able to help.

4 Biology Introduction
You can find more about the operation of COSHH in schools in:
'Safety', by T.P. Borrows, Education in Science, January 1990.
'Science department safety policies - safety X', by R. Vincent and T. P. Borrows,
School Science Review, 73, (264), March 1992.
'Reaction and over-reaction risk assessment in science teaching', by P. Taylor, School
Science Review, 73, (264), March 1992.
'Assessment of risk and school science', by David Tawney, School Science Review
74, (267), December 1992.
The responsibility of school governors for health and safety, HMSO, 1992, ISBN
011886337 1.
The nature of a scientific investigation may involve a degree of independent action by
the student. Our activity sheets for investigations warn students to check safety without
spelling out precautions in detail. Students should be educated to assume responsibility for
safety and always credited in any assessment for making safe plans and carrying them out
safely. All their proposals should be seen by you and you must ensure that you make an
appropriate check, particularly with respect to safety, on what will go on. You will need to
take particular care if students consult library books published before modern safety
standards came into force.
A careful safety check and review by your students is essential when they
are designing and carrying out investigations. The Check safety warning
on the activity sheets will act as a prompt for them. You will need to
monitor your students' plans carefully before they start practical work.
Safety during fieldwork
Some activities can be enhanced by fieldwork. Even the most sensible students in a
classroom can be the most senseless in the field. Equally, fieldwork offers opportunities for
many who achieve little academically to do very well here.
You must clearly arrange proper supervision of your students when they are working
away from the laboratory. This applies as much when they are in the school grounds as
when they are going out on visits. Check school or local authority policy regarding off-site
activities before going ahead.
Seek permission from parents or guardians if the students are going to be working
outside the school grounds. Check that there are no local places which parents might think
of as no go areas. Provide every adult involved in supervising students with a list of names.
Make a preliminary visit to the site of the fieldwork to identify safety hazards. Also check
that local surveys are not going to arouse suspicion or even hostility. Surveys need careful
thought and planning.
Give students a clear code of conduct, remind them of local rules and warn them of any
dangers especially local hazards. Roads and roadsides, and the banks of canals and ponds, as
well as polluted areas of land or water are particularly hazardous.
Remind students never to eat plants, or parts of plants, even if they seem familiar.
Foster an attitude of care and consideration for living things. Whenever possible
animals should be returned to their environment after they have been identified. Avoid
picking flowers or removing parts of plants, unless this is absolutely essential for an
activity.
Students should always be in small groups. They must be warned to wear suitable
outdoor clothing with a waterproof jacket and stout shoes or boots. They should cover any
cuts or grazes with a waterproof, non-allergenic plaster, particularly if they are going to be
working in or near water as this will give some protection against Weil's disease, which is
spread by rats. They should always wash their hands on returning to school after any kind
of fieldwork.
Any equipment taken outside should be robust. Choose bottles, beakers and trays made
of flexible plastics. On sunny days look out for students using lenses to start fires.
Check on specific health problems such as allergies. A simple first aid kit for immediate
remedial measures, for example with cuts and abrasions, should be taken.
Further guidance is available from these sources:
Safety in Biological Fieldwork: guidance notes for codes of practice, ed. D. Nichols,
third edition, Institute of Biology, 1990.

Biology Introduction 5
Poisonous plants and fungi: an illustrated guide, by Marion R. Cooper and Anthony
W. Johnson, HMSO, 1988, ISBN 011242718 9.
'Safety VIII: Safety in out-of-school science', by R. Vincent and J. Wray, School
Science Review, 70, (250), September, 5560, 1988.
Out and about: A teachers' guide to safe practice out of school, by Maureen
O'Connor, Methuen for the School Curriculum Development Committee, 1987,
ISBN 0416 077625.
Safety in outdoor education, Department of Education and Science, HMSO, 1989,
ISBN 011270690 8.
Using and teaching about living things
One of our aims as teachers is to present students with opportunities to develop a reasoned
attitude towards living things. We all meet students with strong views on issues such a
vegetarianism and animal rights. We respect such views while not necessarily encouraging
or challenging them. We can give students the chance to discuss the rights and wrongs of
using living things in scientific investigations.
There are activities in this package which suggest that you bring animal organs into
the laboratory to enhance understanding and to develop curiosity. When doing so, we have
to provide for those who object to seeing, let alone handling, organs from dead animals for
moral, cultural or religious reasons. With this in mind, we have written our activity sheets
to allow alternatives such as models, videos and pictures in books.
Teachers need to be particularly careful over the management of the use of living
things, especially animals, and materials of living origin. We suggest that you tell a class
in advance whenever you will be showing them animal organs so that those who prefer can
come prepared to work with the alternative.
The collection, and certain aspects of the keeping and use of animals and plants in
schools, is regulated by law. Details can be found in:
Animals and plants in schools; legal aspects Department of Education and Science
Administrative Memorandum 3/90 (see 'Addresses'page 141),
Lock R 1981 Investigations with animals and the Animals (Scientific Procedures) Act
1986 School Science Review 71 (255) pp 74-75.
Sensitive issues in the study of inheritance and evolution
Some of the issues raised have important cultural, social and religious implications. As
science teachers we have to be aware of the sensitivity of some aspects of genetics and
evolution for some staff and students. Careful preparation can make teaching the activity
more productive while avoiding unnecessary offence.
Investigating differences between people may provoke overt racial prejudice. You
should be ready to deal with this in line with the schools anti-racist policy. This is a matter
worth discussing at a departmental meeting so that all in the department have agreed
strategies to deal with the problem. You may feel it necessary to get approval for your
strategy from senior management and governors.
The identification of variation in students, particularly if these can be linked with
parentage, needs to be handled with great care. Students are often very sensitive when
identified at the extremes of the range investigated, such as weight and height.
Some students and teachers have religious beliefs which reject the theory of evolution,
and in a few schools this is such a major issue that governors will determine policy about
the treatment of the topic in the curriculum. Elsewhere the acknowledgement of people's
views is often sufficient when introducing such sensitive topics. A few parents, however,
may want to withdraw their children from any treatment of this theory. Parents are
generally well aware that this material is covered in the National Curriculum and do not
wish to put their children at a disadvantage. Even so, it is worth finding out beforehand
whether certain students are withdrawn from religious assemblies or RE lessons.
Sometimes it helps to contact parents in advance to give them a chance to review the
course publications before the topic comes up in class.
Another area of sensitivity concerns heredity and any activities which might require
students to reveal details of their home lives. Many students do not live with their natural
parents and references to their mother, father, sisters and brothers can be embarrassing.

6 Biology Introduction
Some students answer the question 'How many brothers and sisters have you got?' with 'It
depends'. You cannot assume that children from the same family within the school have the
same natural parents.
Bear in mind that off-the-cuff remarks about families can cause great pain to students
who were abandoned as infants, whose families have experience of child abuse, or who have
discovered that they were adopted.
The treatment of hereditary diseases also requires careful handling. School records will
generally identify students concerned. You may be asked about other hereditary diseases
which run in local families. If so, it is generally better to plead ignorance or refer the
individual to another authority than to risk giving misleading or worrying information.
You will have to take care when setting cover work for absent colleagues in this topic.
Some activities are better avoided in these circumstances unless the supervising teacher is
aware of the difficulties and equipped to deal with them.

Nuffield Biology Section Bl
Life processes: an overview
Context
Biology is the study of living organisms. This section introduces students to the life
processes of familiar plants and animals. Each of these processes will be considered in detail
at a later stage of the course.
There are no Nuffield activities directly associated with this section.

Nuffield Biology Section B2
Levels of organization
Context
This section provides opportunities for students to develop their knowledge of how living
things are organized. It studies the similarities and differences between plant and animal
cells and how they are grouped into tissues, organs, and organ systems to form a functional
unit.
B1 Skill sheet - Using a microscope
Students may need a lot of help to work through these instructions for the first time. It
would be useful to translate them into a simple flow-diagram on the board.
Most students will have little idea about the sizes of specimens. Calculating the diameter
of the field of view will help them. This can be repeated for each objective lens.
This might be a good time to talk about orders of magnitude, using examples from the
table on the next page.
Safety notes
1 At least once a year, a competent person must check the electrical safety of microscopes
with integral mains electric light sources or separate electric light sources. A record of these
inspections must be kept.
2 Do not use daylight as an alternative to a bench lamp. Severe damage could be caused to
the eye if sunlight is focused through the instrument.

B2 Levels of organization 9
Orders of magnitude
Average dimensions of biological structures
Multiple of
the metre, m
m
mx 10-'
m x 10~2
m x 10- 3
m x 10-4
m x 10-5
m x 10-6
m x 10-7
m x 10-8
SI units
m
metre
dm
decimetre
cm
centimetre
mm
millimetre
Jim
micrometre*
Dimensions in
standard form
3.0 x 10° m
1.7 x 10° m
6.0 x 10- 1 m
1.1 x 10-' m
5.0 x 10-2 m
4.4 x 10-2 m
3.5 x 10-3 m
9.0 x 10-3 m
1.5 x lO-'m
1.0 x lO^m
7.5 x 10-5 m
1.0 x 10-5 m
7.5 x 10-6 m
2.0 x 10-6 m
5.0 x 10-7 m
l.Ox 10-8 m
Dimensions in
SI units
3.0m
1.7m
600mm
110mm
50 mm
44 mm
3.5 mm
9.0 mm
150 |im
100 (im
75 (im
10 p.m
7.5 p.m
2.0 nm
500 nm
10 nm
Height of elephant
Height of man
Length of gull's wing
Length of sparrow's
wing
Length of striated
muscle cell
Length of 3-month-old
human foetus
Length of 1 month old
human embryo
Length of housefly
Length of flagellum
Diameter of human
egg cell
Diameter of striated
muscle cell
Length of chloroplast
Length of cilium
Diameter of bacterium
Diameter of
chloroplast
Diameter of small
virus
* Older books may refer to p.m simply as |i (microns) and to nm as
t Angstroms are not S.I. units but will be found in older texts.
(millimicrons).
B2 Cells and what they do
REQUIREMENTS
Students will need:
activity sheet
Skill sheet B1 - Using a microscope
microscope
prepared microscope slides of body cells
slides of plant cells for comparison
textbooks with photographs of cells and descriptions of functions
Notes on the activity
Students relate the structures of cells to their functions. The hierarchy of organization, from
cells to organisms, is also illustrated. Various collections of high quality photographs of
cells are now available in books and magazines and can help to support this activity.
You can help students to think about cells in three dimensions by asking them to make
cell models. Ask them to make their models out of anything they have at home. Typically
they might use old shoe boxes painted and coloured with netting for the endoplasmic
reticulum and blobs of Plasticine for organelles with clingfilm for membranes. This can be
a homework activity for those working at higher levels but is worth spending class time

10 B2 Levels of organization
with some students. If so, students will need access to a range of materials such as
cardboard, plastic bottles, yoghurt pots together with string, Plasticine, clingfilm, odd bits
of plastic, old netting, newspaper and tracing paper together with scissors, 'solvent free'
glue, Sellotape, paint, and 'solvent free' felt-tip pens.
B3 Body systems in Daphnia
REQUIREMENTS
Students will need:
activity sheet
Skill sheet B1 - Using a microscope
beaker
microscope
microscope slide
Access to:
Daphnia (see note)
cotton wool (a few strands on a slide can help to slow down the Daphnia )
textbooks giving characteristics of Crustacea, and Daphnia
Note:
Daphnia are available from tropical fish shops. Aerate the water if you are going to keep
them for some time.
Notes on the activity
This activity revises the characteristics of
living things, and relates these to
specialized body systems. It may be enough
for students to observe and describe
Daphnia or you may want to encourage
more of an investigative approach to find
out some of the effects of environmental
changes on Daphnia.
Daphnia are reasonably tolerant of
experimental work though they must not be
overheated by the microscope lamp. If they
come from a tropical fish shop, they were
bred to be eaten by fish. Even so, one of
our aims should be to present students with
opportunities to develop a reasoned attitude
towards living things. Some students hold
strong views on animal rights and will
question the rights and wrongs of any
experimenting on live animals. They may
want to discuss the question 'Is there any
difference between experimentation with
Daphnia and experimenting with rabbits or
monkeys?'.
The 'if you have time' question will
show students how plants and animals have
rather different ways of supplying the same
needs.
legs inside
body shell
anus
antenna
A diagram of Daphnia with some of the body parts labelled.
heart
embryo
brood chamber

B4 Body systems in animals
B2 Levels of organization 11
REQUIREMENTS
activity sheet
books and/or CD-ROM giving structure and function of animal systems
Notes on the activity
This activity is suitable for private study or homework. It provides an opportunity to
develop information-gathering skills, using library books or CD-ROM.
Extension work could include a comparison of a single system in two animals, such as
skeletal system in elephant and gazelle, digestive system in pig and cow, breathing system
in pig and bird, circulatory system in rat and fish.
backbone
shoulder blade
oesophagus
gall bladde
bile duct
pancreas
anus
large intestine
stomach
Elephant
brain
pharynx
nasal cavi
nostril
mouth cavity
touch
sensors
pulmonary
aorta
vena cava
kidney
mouth'
Earthworm (front end)
nerves
nerve cord
carotid artery
I
jugular vein
liver pancreas'small intestine
large intestine

Nuffield Biology Section B3
Nutrition in plants and animals
Context
This section examines the physiology of photosynthesis and how it relates to food
production. Photosynthesis is the fundamental process which transfers light energy into
chemical energy that is stored in complex organic molecules for use by the plant or other
organisms.
Digestion is a means of breaking down complex organic molecules into smaller soluble
units prior to absorption into the body.
The role of enzymes in catalysing biological reactions is explored experimentally with
reference to digestion.
B5 How do gases get in and out of leaves?
REQUIREMENTS
Each group of students will need:
a variety of leaves (simple, palmate, pinnate, hairy, waxy)
iris or other monocot leaf for the extension work on disc
access to freshly boiled water
glass beakers, 250 ml
forceps or tongs
microscopes
Sellotape
nail varnish (pink rather than clear or opaque)
microscope slides
plastic rulers (clear) with mm scales
Notes on the activity
The worksheet is self explanatory. If hot water is suppled from a kettle, there should be no
hazards with the use of nail varnish. If Bunsens are used to heat water, the nail varnish part
of the experiment should not be performed until the Bunsens are extinguished. Teachers
should fill the beakers with hot water on the benches. Pupils should be warned of the
dangers of trying to pick up beakers of freshly boiled water.
Using Sellotape to remove the dry nail varnish is quite straightforward. Pupils should
take care not to touch the sticky surface of the Sellotape. Good results can be obtained
using the packs of assorted lettuce leaves which are sold in many supermarkets. Different
varieties of lettuce produce very varied results. Leaf peels can also be made from lettuces
relatively easily by tearing the epidermis off the mesophyll layer.
On disc
Extra questions on the number of stomata per mm2 and the stomata on a monocot leaf.
B6 Photosynthesis
REQUIREMENTS
Students will need:
activity sheet
suitable textbook

Notes on the activity
The activity builds on work in Key stage 3.
The activity presents a working hypothesis which students can use as a basis for
investigations in the next group of activities. The concepts are difficult and some students
will need a lot of help.
Students working at the higher level need to know the symbol equation that tells them
that:
overall, six molecules of carbon dioxide and six molecules of water react to make one
glucose molecule,
glucose is a compound of carbon, hydrogen and oxygen,
for every molecule of carbon dioxide, photosynthesis produces a molecule of oxygen.
Some students working at this level could express this in terms of moles.
Answers to questions
1 Energy for photosynthesis comes from the Sun.
2a We use the iodine test for starch because it is quick, easy and gives a clear result. As
soon as plant cells start making glucose by photosynthesis they convert some of this sugar
to starch, which can be stored. So finding starch in a leaf is good evidence for
photosynthesis.
b Glucose made in the leaves travels through stems to other parts of a plant. A potato
plant, for example, makes glucose in its leaves above the soil but stores starch in tubers
underground. So finding starch in some plant tissue does not mean that photosynthesis
happens in that part of the plant. Students could be asked to consider what happens when
potatoes turn green.
3 Some of the factors which might affect the rate of photosynthesis are:
the brightness of the light shining on the leaf,
the colour of the light,
the temperature,
the concentration of carbon dioxide in the air.
Opportunities for co-ordination
P62 looks at energy transfer by radiation.
C9 explains word equations.
CIO explains symbol equations for students working at the higher level.
C26 discusses radiation.
Other resources
NCS Biology Chapter B3.
B3 Nutrition in plants and animals 13
B7 Skill sheet - Testing for starch
REQUIREMENTS
Students will need:
skill sheet
plant material
forceps
beaker
boiling-tube
Bunsen burner with tripod, gauze and mat (see note 1)
Petri dish
white tile
anti-bumping granules
eye protection

14 B3 Nutrition in plants and animals
Access to:
ethanol or propanol - FLAMMABLE (see note 2)
iodine in potassium iodide solution in dropper bottle - HARMFUL (see note 3)
jar labelled 'waste ethanol' to collect green ethanol from students (see note 2)
Notes:
1 If available, an electrically-heated water bath is safer and more convenient than a beaker
of hot water for heating the tube of ethanol. Water from a kettle is much safer than using a
Bunsen burner.
2 The waste solution of chlorophyll in ethanol could be used as a future source of
chlorophyll. Ensure that the jar labelled 'waste ethanol' cannot be tipped over and is in a
safe place so that it does not become a fire hazard.
Propanol has a higher flashpoint than ethanol and is therefore safer. It is also better at
extracting chlorophyll.
3 Grind 1 g iodine and 1 g potassium iodide with distilled water in a mortar. Make up to
100 cm3 . Dilute 5 cm3 of this solution with 100 cm3 water to prepare the test reagent.
Note: solid iodine can cause skin burns if left on the skin for some time. Avoid inhaling
iodine dust.
B8 Plants we eat
REQUIREMENTS
Students will need (in addition to those listed under B7):
activity sheet
skill sheet B7
Access to:
a selection of plants we eat (see sheet)
reference books with information on the parts of plants used for food and ways of cooking
plants
Notes on the activity
Students must not attempt to eat any of the plant material. You might invite students to
bring samples of fruits and vegetables from home for testing. This might lead to a
discussion of the social and cultural reasons why different families eat different foods.
Students may note the extent to which the variety of plant produce in our supermarkets
depends on imports from all over the world.
The discussion of foods leads to discussion of the parts of the plants concerned and their
function. The questions could be set as a follow-up homework to the practical activity.
Answer to questions
People eat many different parts of plants as the table opposite shows.

B3 Nutrition in plants and animals 15
Stem
kohlrabi
bamboo shoots
asparagus
Roots
sugar beet
parsnips
beetroot
radish
cassava
carrots
horseradish
Leaves
mustard and cress
water cress
lettuce
parsley
chives
tea
rosemary
leeks
Flower buds
Brussels sprouts
capers
Bulbs (stems
with swollen
leaf bases)
onions
garlic
Flowers
cauliflower
sprouting broccoli
saffron (just the
styles)
globe artichokes
Leaf stalks
celery
rhubarb
Fruits
black peppercorns
coriander
vanilla
sweetcorn
dates
sultanas
olives
apples (false fruits)
oranges
banana
runner beans
cucumbers
marrows
aubergine
okra
Tubers (swollen
underground
stems)
potato
sweet potato
yam
Jerusalem
artichokes
Seeds
peas
broad beans
coffee beans
cocoa beans
almonds
walnuts
soya beans
white pepper
These pictures show cultivated varieties of one plant species. They are all Brassicas.
Students can see the similarities if they let the plants flower. All the plants produce yellow
flower spikes with a similar structure.
Spring cabbage - leaves. Photosynthesis
happens in the leaves.
Cauliflower-flowers. The
flowers contain the sex
organs and produce seeds if
fertilized with pollen.
Kohlrabi - stems. The stems
support the leaves and flowers,
they carry water from the roots
to the leaves and also transport
sugars from the leaves to other
parts of the plant.
Brussels sprouts - flower buds. The flower buds
protect the delicate flowers as they develop.

16 B3 Nutrition in plants and animals
Plants make glucose by photosynthesis in sunlight. Plants can make plenty of glucose in
the summer months when the weather is warm and the Sun is bright. They convert much of
the glucose to starch to be stored. Stores of starch can keep a plant going through the
winter or give a seed the energy reserves it needs as it germinates.
Students will find starch with the iodine test in some energy foods. Examples include:
carrots, potatoes, corn on the cob, wheat grain, and rice.
1 Rice, bread and potatoes are 'staple' foods which meet part of our basic energy needs.
They are all plant foods. People, like other animals, depend on plants because they are the
'producers' which make glucose by photosynthesis. Animals eat plants or eat other animals
which live off plants. Without plant life there would be no animal life.
People need vitamins for healthy growth and we get our vitamin C from plants,
especially citrus fruits and potatoes. Plant foods, such as spinach and wholemeal bread, can
also be a good source of minerals including iron.
Fibre in the diet helps our digestion and protects against heart and bowel disease. Fibre is
the cellulose in plants which we cannot digest. Green vegetables, fruit, beans and
wholemeal bread all add fibre to our diet.
2 One example, (seeds) could be answered as follows:
Seeds, e.g. peas, beans, lentils, have a store of starch and protein. These are used when the
seed germinates, until it has developed leaves to make its own food by photosynthesis.
Respiration to
^^^^ provide energy
Su 9 ars
Stored
starrh
digestion
~~~*"
translation ^^^
———————"-^
siarcn to embryo ^~^~^^__^ Built up into
^~~*' cellulose for
walls of new cells
Stored digestion^ amino
protein
acids
translocation
—————— >•
to embryo
Enzymes
* to control
Built up /' metabolism
into new in cytoplasm
proteins N
\^ Structural
proteins in
cytoplasm
3 Gardeners control the environment in which their crops grow. They water their crops and
supply nutrients by digging compost, manure or manufactured fertilizers into the soil. They
hoe around growing plants to stop weeds competing for water and nutrients. Gardeners are
also on the look-out for insect pests which attack and weaken crops. Gardeners protect some
crops by growing them in warm and sheltered places, such as up a south-facing wall or in a
greenhouse.
Gardeners can choose different varieties of crops. Varieties vary in their size, taste, rate of
growth, resistance to disease and ability to survive cold weather.
4 Plant cells have walls of cellulose. Uncooked, fresh vegetables are crisp and crunchy -
they may be too hard to eat. Students can feel the difference if they bite into a raw carrot and
compare it with a cooked carrot. People cannot digest cellulose. Cooking softens cell walls
and breaks them down so that our digestive enzymes can get at the nutrients inside plant
cells more easily. But the cellulose cell walls are completely permeable, so digestion can
still take place even when the walls are intact.
Some foods have toxic chemicals which are made harmless by cooking. Examples are
hydrogen cyanide in cassava, alkaloids in yams, and 'vicine' in broad beans.
6 Proteins are made up of about twenty different kinds of amino acid. Our bodies can
change some of these into others. But for adults there are eight essential amino acids (ten
for children) which we cannot make, so we need to eat them regularly.
All these essential amino acids are found in all protein from animals (meat, milk
products, eggs). Plant proteins are short of some of them - for instance, most beans are
deficient in methionine, and most grains are deficient in lysine.
People in each continent have developed their own combination of foods, which have
formed the staple diet for a good thousand years (long before the discovery of amino acids!).
People in the Americas eat corn and black beans, Asians eat rice and soya beans, Europeans
eat wheat/barley and peas/lentils.

Students could collect recipes to illustrate these combinations. Another solution is to add
animal products to plant protein, e.g. macaroni cheese, rice pudding made with milk.
B3 Nutrition in plants and animals 17
B9 Do plants and animals alter the environment around them?
REQUIREMENTS
Each group of students will need:
Elodea, free of dirt
filamentous algae, about 5 cm long
water animals, such as water snail or Gammarus
hydrogencarbonate indicator solution, diluted 1 part in 10, equilibrated with atmospheric
carbon dioxide
lightproof box or cupboard
means of labelling tubes
light source
specimen tubes, 11 flat-bottomed, 7 cm x 2.5 cm or 11 boiling-tubes
11 bungs
Notes:
Tubes should be very carefully washed and rinsed in N/100 KHCO3 . The plants and animals
should also be rinsed in this solution, to prevent a colour change due to acids on their
leaves or exoskeletons.
This experiment should run for 12 hours so it may help to set it up beforehand.
Freshly prepared indicator solution should be used. Useful comparisons can be made if
three tubes are prepared beforehand to show the colour of the indicator when in equilibrium
with atmospheric air (normal levels of carbon dioxide), with exhaled air (increased levels of
carbon dioxide) and with air containing no carbon dioxide. This can be done as follows:
1 Stoppered specimen tube with indicator solution, to show colour in contact with
normal air.
2 Stoppered specimen tube with indicator solution, which was breathed into before the
stopper was inserted.
3 Specimen tube with indicator solution, above which some granules of soda lime are
held in place in a piece of muslin wedged in position by the stopper. (This should be set up
some hours in advance.) Alternatively, blow ammonia vapour (corrosive) over the indicator,
in a fume cupboard, until it turns deep maroon. This only takes a few minutes.
Notes on the activity
For a full interpretation of the changes in
the levels of carbon dioxide in the tubes it
is necessary to establish that animals and
plants respire (and thus produce carbon
dioxide) all of the time, but plants also
photosynthesize in the light, and take in
carbon dioxide. In bright light, the rate of
photosynthesis of plants exceeds the rate
of respiration of both plants and animals,
so that levels of carbon dioxide in the
tubes actually fall, as shown by the purple
colour of the hydrogencarbonate indicator.
You may decide to use this experiment as
the starting point for an investigation.
Opportunities for co-ordination
C52 discusses the development of the Earth's atmosphere.
Other resources
Pathways Sourcebook Environment page 7 gives information about Biosphere 2.
photosynthesis
respiration
0 6 12 18 24
Time in hours
Changes in levels of photosynthesis
and respiration over 24 hours.

18 B3 Nutrition in plants and animals
B10 What affects the rate of photosynthesis?
REQUIREMENTS
Students will need:
activity sheet
beaker, 400 cm3
metre ruler
Elodea or other oxygenating pond plants (see note)
knife or solid scalpel
electric lamp
paper clip
M/200 potassium hydrogencarbonate solution which has had oxygen bubbled through it
Prompt sheet (on disc) if you are using this as a Scl investigation
Students may also need:
hot water
thermometer, 0-100 °C
potassium hydrogencarbonate solution
coloured filters
different types of light bulb
push-button counter for counting bubbles
Note:
You need fresh pond weed and will get better results if you shine a bright light on it for a
few hours before the lesson.
Safety note
This is an open investigation and teachers are reminded of the need to check for safety in
line with the general comments at the front of this guide.
Notes on the activity
When comparing the effects of different light intensities,remember that the ambient light in
the lab will affect the results. The size of the bubbles depends on the cleanness of the cut.
The aim is to get a steady stream of small bubbles. Students may need prompting to leave
enough time between counts to allow the pond weed to adjust to the new conditions.
You might ask your students why an 'ordinary' green leaf would not work for this
investigation. Consider the use of leaf discs instead of whole leaves. They float up as
oxygen is produced.
There is a lot of scope for simple experimental design in this activity. The use of
coloured filters with this experiment is particularly effective. Adding sodium
hydrogencarbonate is equivalent to increasing the concentration of carbon dioxide. Aquatic
plants probably take up carbon dioxide in the form of hydrogencarbonate ions.
If you use this experiment as the basis for a Scl investigation, it could well be the first
investigation in year 10. It would be worth spending time revising what is meant by a
pattern in the results, a prediction, a theory and a law.
Another word for pattern is generalization. Here are some examples of
generalizations from the work of scientists studying the environment:
when the atmospheric pressure rises we often have still dry weather in the UK,
green leaves in sunlight take in carbon dioxide and give out oxygen,
carbonate rocks fizz and give off a gas when you spot them with an acid,
shrubby lichens only grow in areas where the air is free of pollution.
Generalizations are sometimes called laws. Boyle's law, for example, tells us how gas
volumes change as the pressure changes. The pattern is quite a simple one: double the
pressure and you halve the volume (so long as you keep all other variables the same).
Scientists try to dream up theories to explain their generalizations (patterns).
Examples:
the theory of photosynthesis explains the way in which leaves exchange gases with the
air,

the 'particles-in-motion' (kinetic) theory of gases explains the gas laws including
Boyle's law.
When scientists come up with a theory they often use it to make predictions. Then
they can do experiments to see if the predictions work out. Their experiments help to test
out the theory.
Some students will need to be reminded of the language used to describe variables. This
is included on the prompt sheets.
We include three prompt sheets on the disc, aimed at three broad bands in the
Statements of attainment of Scl.
Students may need guidance on the range of a variable to study. For instance, a rise of
10 °C will double the rate of many biochenical reastions. A rise in temperature will also
increase the solubility of carbon dioxide and decrease the solubility of oxygen. They may
also need to be told that we are studying 'optimum range'. If the temperature is too high
photosynthesis is affected (though for a different reason than when the temperature was too
low). For these reasons variables must be measured quite accurately.
Opportunities for co-ordination
P44 'Exploring the spectrum' considers the spectrum, concentrating on infra-red and ultraviolet.
Other resources
Nuffield Science Calculations, Topic 43 (Graphs and tables) shows how to present and
analyse the results.
B3 Nutrition in plants and animals 19
On disc
Prompt Sheet A )
Extra help A )
Prompt Sheet B )
Extra help B )
Prompt Sheet C )
Extra help C )
easy
average
more difficult
B11 Factors affecting photosynthesis (H)
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
You might set this activity as a homework. The questions on photosynthesis are relatively
difficult. Interpreting the data can help to suggest ideas for investigations to students aiming
for the high Scl levels.
Answers to questions
la The graph shows that light intensity, temperature and the concentration of carbon
dioxide in the air all affect the rate of photosynthesis.
b Below 70 units in investigation B, the light intensity limits the rate of photosynthesis.
c At 75 units in investigation B, the concentration of carbon dioxide limits the rate of
photosynthesis. Investigation A shows that increasing the carbon dioxide concentration at
the same temperature increases the rate.
d Investigation C. Summer time temperatures in Britain are about 20 °C and the normal
concentration of carbon dioxide in the air is about 0.03 per cent.

20 B3 Nutrition in plants and animals
2a The cotyledons.
b The cotyledons store starch and protein. Both are digested and carried, in the phloem
vessels, to the growing points of the shoot and, to a lesser extent, the root. Amino acids
from the digested proteins are used to make proteins in the cytoplasm of the new cells, so
there is no change in mass.
Some sugar from the digested starch is used to make cellulose for the cell walls. But
some is used for respiration, resulting in a loss of mass. In the dark this is not replaced, but
in the light it is replaced by photosynthesis.
By day 29, in the light most of the mass is in the shoot. The cotyledons have
shrivelled to a mass of only 0.03 g.
ScO
1 c work quantitatively
B12,B13,B14 The food tube
REQUIREMENTS
Each student will need:
activity sheet and diagram sheets B12, 13, 14
scissors
paper glue (solvent free)
Notes on the activity
You might supplement this activity by showing your students tripe from a butcher to give
them a clearer picture of the inner wall of the gut. If you do, you need to be alert to the
religious, moral and cultural sensitivities in the class when handling material from dead
animals.
Answers to questions
The food we put in our mouths is often insoluble and has to be broken down into smaller,
soluble particles. This is called digestion. The smaller particles (molecules) can then go
through the gut wall and into the bloodstream. The blood carries food to all parts of our
body.
Enzymes speed up the chemical reactions involved in
digestion. Each enzyme works for a different type of food.
Amylase is the enzyme in saliva. It speeds up the breakdown
of starch. Starch molecules are large - they are long chains of
sugar molecules. Enzymes help to change large starch
molecules into small sugar molecules. Cellulose is also a
carbohydrate with large molecules. Enzymes made by the
human gut cannot break up cellulose into sugars. Fat
molecules are big too. The gall bladder releases bile. Bile
emulsifies the fat, breaking it up into small droplets. This
makes digestion by the enzyme, called lipase, easier. Fat is
broken down to glycerol and fatty acids. Students may have
heard of the fatty acid called stearic acid.
Protein molecules are long chains of about 22 different
amino acids. The pancreas releases enzymes called proteases
which break down proteins to amino acids.
Digestion begins in the mouth and continues in the
stomach. Then muscles in the wall of the gut squeeze the
food, moving it along the tube. Most absorption of small
molecules takes place in the small intestine. Most water,
however, is absorbed in the large intestine. In this way
soluble food and water get into the bloodstream to be taken to
the tissues.
oesophagus
liver.
gall_
bladder
small
intestine
appendix
anus_
_salivary
glands
diaphragm
_stomach
pancreas
large
intestine

We cannot digest all the food we eat. The large intestine stores undigested food, such as
cellulose, before it passes out of the anus as faeces. The movement of faeces through the
intestine is easier if it is full. Complex carbohydrate (sometimes called dietary fibre)
provides the bulk for muscles to squeeze against and keep the faeces on the move.
The meal of fish, peas and chips contains most of the requirements of a balanced diet:
Energy - from fat in chips
- from carbohydrate in chips and peas
Protein - fish and peas
Vitamins
Minerals
- C in chips
- calcium in peas
- iodine in fish
- iron in peas
- potassium in chips, peas and fish
Fibre - peas and chips
But:
less fat would be more healthy, and don't add extra salt.
The meal could be improved by adding fresh fruit to give more vitamin C and fibre. Also, a
drink made with semi-skimmed milk to give vitamins A and D, plus more calcium.
Other resources
NCS Biology Chapter B4, B5.
B3 Nutrition in plants and animals 21
B15 Enzymes and digestion
REQUIREMENTS
Each group of students will need:
activity sheet
4 x 15 cm lengths of Visking tubing (see note 1)
4 boiling-tubes
4 syringe barrels (see note 2)
funnel
2 test-tubes in rack
5 beakers to use as water baths (for boiling-tubes and Benedict's test)
tripod and gauze
thermometer
Bunsen burner, heatproof mat and beaker (to use as a water bath for Benedict's test)
eye protection
Access to:
fresh starch suspension (10 g/1) (see note 3)
concentrated glucose solution (10% or more)
amylase solution (see note 4)
Clinistix (see note 5) or Benedict's reagent
iodine solution

22 B3 Nutrition in plants and animals
Notes:
1 You will save on Visking tubing if groups cooperate,
with each group setting up one of the four
tubes.
2 The end of an old syringe makes a support for the
Visking tubing, allowing it to sit conveniently in a
boiling tube. Samples of the contents of the tubing can
easily be taken with a pipette. Some students may have
time to sample the contents of tube 3, to show the
reduction of starch, as sugar is produced.
V
3 Use soluble starch, free of sugars. Make a cream of
5 g soluble starch in cold water. Pour into 500 ml
boiling water and stir well. Boil until you have a clear
solution.
4 Diastase is a mixture of alpha and beta amylase. It is cheap and has low activity but it
contains maltose and gives a positive reducing sugar test. A solution containing 3%
saw off
the barrel
of an old
syringe
diastase in 0.8% saline gives a result in this investigation but students interested enough to
run an enzyme-only control will find that this is not a fair test. Beta amylase is from barley
and also gives a positive reducing sugar.
Alpha amylase is bacterial amylase with high activity but more expensive and does not
give a positive reducing sugar test. You can use lower concentrations of this enzyme.
5 Clinistix are relatively expensive but they are quick and easy to use. Each stick can be
cut into two or three pieces.
Notes on the activity
Many students will need help to understand this activity so you might decide to do this as a
demonstration with students helping to set up the model gut and carry out the tests. When
interpreting the results students have to think in terms of two types of model: the model
gut with Visking tubing representing the selectively permeable membranes lining the gut
wall, and a simplified chemical model of large and small molecules. A further complication
is that the movement of chemicals is unseen and only inferred from the results of chemical
tests. An additional model could be used, with chicken wire to represent the membrane and
poppet beads, in chains to represent starch and singly to represent glucose.
Answers to questions
1 The water in the beaker at 37 °C represents the
bloodstream at body temperature.
2 In tube 1 no starch appears in the water. Starch particles
(molecules) cannot get through the very small holes in the
Visking tubing.
In tube 2 sugar appears in the water. Sugar particles
(molecules) are much smaller than starch particles. They are
small enough to get through the holes in the tubing.
In tube 3 the enzyme amylase gets to work on the starch,
breaking it down to sugar (mainly maltose). The sugar gets
through the Visking tubing into the water.
In tube 4 neither sugar nor starch appear in the water.
3 Starch particles (molecules) are like a long necklace of
'beads'. The 'beads' in the chain are sugar (glucose) molecules.
The gut wall is a bit like a sieve. Large molecules like starch
can't get through.
Enzymes break up starch chains by snipping off the
glucose 'beads'. The smaller pieces can get through the gut
wall into the bloodstream. Cells in the body need glucose and
oxygen for respiration, which is their source of energy.
long chain
starch
molecule
o
small sugar -
molecules split
off from starch
water
molecu
D O
Do
0
D
0
Visking tubing
with holes which
let through small
molecules of water
and sugar

Amylase in saliva snips off the glucose units in pairs. A pair of glucose units is a
molecule of a sugar called 'maltose'. Other enzymes complete digestion as food moves
through the stomach and intestines. These enzymes split maltose into single glucose
particles.
4 Starch molecules are too large to pass from the gut into the bloodstream. Digestion
breaks up big starch molecules into small glucose molecules. Glucose molecules are small
enough to get into the blood.
Opportunities for co-ordination
C55 explains rates of reaction.
C56 investigates the effects of catalysts on rates of reactions.
B16 More about digestive enzymes
REQUIREMENTS
Each student will need:
activity sheet
eye protection (see note)
Note:
As all the investigations in this activity are likely to be going on at the same time, all
students should wear eye protection.
B3 Nutrition in plants and animals 23
Trypsin investigation
For the approach suggested on the help sheet each group of students may need:
beaker, 250 ml to act as water bath
2 test-tubes
thermometer
stirring rod
insulating fabric
knife
Access to:
exposed black and white photographic film
trypsin solution (see note)
sodium hydrogencarbonate solution (0.05 mol/1)
hot water from kettle or tap
labels
Note:
1 Prepare trypsin solution by adding a level teaspoonful of trypsin to 250 ml cold water.
Stir to dissolve completely.
2 Not all film has a suitable protein gel. Philip Harris supplies suitable film. Old X-ray
film can also be used. Test it first! A strip of film can be suspended in a test-tube, using a
bent paper-clip, so that half is submerged in the trypsin solution and half is exposed for
comparison.
The rate of digestion is sensitive to temperature so students should keep the water close to
40 °C. They will notice significant digestion in 20 minutes or so. Complete digestion will
take about an hour at 40 °C. Avoid temperatures as high as 60 °C since the gelatin will
dissolve, giving the same appearance as that resulting from enzyme action.
Left overnight, trypsin digestion will continue even at room temperature so it is worth
keeping the tubes for students to examine at the next lesson.

24 B3 Nutrition in plants and animals
Amylase investigation
Depending on their plans each group of students may need:
beaker, 250 ml to act as a water bath
2 test-tubes in rack
white spotting tile
glass rod
thermometer
Bunsen burner, tripod, gauze and heatproof mat
stopclock or stopwatch
1% solution of NaHCOj, NaOH, HC1
Access to:
amylase solution
iodine solution in dropper bottle
This reliable technique provides students with a good system to explore the effects of
temperature or pH on enzyme activity.
Lipase investigation
Access to:
milk (perhaps different kinds, including full cream, semi-skimmed and skimmed)
labels or marker pens for test-tubes
phenolphthalein in dropper bottle (1 g in 200 ml ethanol)
5% lipase solution (see note)
sodium carbonate solution, 0.05 mol/1
distilled water
buffer tablets (e.g. tablets for pH4, pH 7 and pH 9.2)
Depending on their plans each group of students may need:
4 test-tubes in rack
dropping pipette
syringe (for measuring liquids)
Bunsen burner, tripod, gauze and heatproof mat
test-tube holder
stopwatch or stopclock
thermometer
glass stirring rod
washing-up liquid
Note:
The lipase solution is best freshly made but it will keep for a day or two in a refrigerator.
With the quantities suggested, the pink colour in the tube with fats and the enzyme will
disappear after about 4 minutes. Digestion of fats produces fatty acids which neutralize the
alkali, sodium carbonate, and lower the pH until phenolphthalein loses its colour. Universal
indicator could be used as an alternative, or a pH probe and data logger. Washing-up liquid
could be added, to emulsify the fats, providing a larger surface area for enzyme action. This
will demonstrate the effect of bile salts.
Students start by trying out one of the enzymes as a demonstration, then they could
design an investigation of their own. Some students may simply do the demonstration and
not go on to an investigation at this stage. There is a structured help sheet (side 2) for those
who need extra guidance which also asks questions to remind students of the Scl language
of variables. The help sheet uses albumen and trypsin.

B3 Nutrition in plants and animals 25
Answers to questions
1 Enzymes can make chemical reactions in our bodies go much faster. They are
biological catalysts.
We can use various models to explain how enzymes work. One model likens chemical
reactions with enzymes to turning a key in a lock. Just as you have to have the right key to
fit the lock, so you have to have the enzyme with the right shape for the chemicals
involved in a reaction. A better analogy is a hand fitting into a glove.
reacting
molecule (key)
products after
reaction
enzyme molecule
(lock)
enzyme ready to
catalyse the
reaction again
High temperature, or the wrong pH, can change the shape of an enzyme and make it useless
- the key no longer fits the lock.
No one model describes exactly how enzymes work. Each model has its good points
and is particularly good at describing one aspect of the way enzymes speed up reactions.
Enzymes get molecules close enough together to react. Enzymes also help to bring about
the same chemical change over and over again. This is where the idea of comparing
enzymes to a molecular dating agency comes in.
Some enzymes act by joining on to the reacting molecules and changing them about in
such a way that they can react and turn into something new. The new molecules break away
from the enzyme leaving it ready to work on more molecules. Some people like to compare
enzymes like this to mechanics working on a racing car during a pit stop.
The process above
could be likened to
driving into a garage
.... where wheels can change
places, improving efficiency
of car
2 An enzyme is produced in an inactive form so that it does not react with the cells of the
digestive gland itself.
Opportunities for co-ordination
There are links with the study of catalysts in Chemistry.
B17 The value of villi(H)
REQUIREMENTS
Each group of students will need:
graph paper, pencils, rulers

26 B3 Nutrition in plants and animals
The procedure is detailed on the worksheet.
Answers to selected questions
2 Between 4 and 8 years old.
3 The healthy boy grew 20 cm in this 3-year period, the boy with coeliac disease only
10 cm. Yearly rates of growth are therefore 6.67 cm and 3.33 cm respectively. Rates
calculated from the graph will, of course, depend upon its accuracy.
4 The healthy boy grew twice as fast.
5 The data is useful in showing fluctuations in growth rate, related to the boy's diet.
However, a sample of one healthy boy and one with the disease is very unreliable,
considering the wide range of heights among boys of the same age, and the wide range of
ages at which they grow, during puberty. There could be many other explanations, both
inherited and environmental, for the differences between the two boys. A much larger
sample is needed.
6 Almost all the commonly observed clinical features of coeliac disease arise as a
consequence of poor absorption of food. They include loss of body mass, diarrhoea, muscle
weakness, skin abnormalities, anaemia and, in children, a failure to grow.
7 He must be given a gluten-free diet for the rest of his life.
It is worth noting that some baby foods are gluten free, and point this out on their labels.
Pupils could be asked to look out for these and to bring the labels into school.
Other resources
NCS Biology Chapter B5.
Further information about coeliac disease may be obtained from The Coeliac Society,
PO Box 220, High Wycombe, Bucks HP11 2HY
B18 Foods and food tests
REQUIREMENTS
The teacher may need:
small quantities of cellulose, pectin, and wheat bran
4 beakers, 100ml
glass rod
cellulose wallpaper paste, about 10 g
measuring cylinder, 100ml
beaker, 250 ml
Notes on the activity
This is a simplified version of a 'concept map'. The words have already been put into an
order which will help students to make the connections. But many concept maps could be
much more open-ended. The words could be written on small pieces of paper, which
students, in groups of three or four, could arrange, stick on paper and draw connecting lines.
Lines can be labelled to explain the relationship between the words. This is a valuable
group activity, either at the start of a topic, to find out what students already know, or as a
means of revision at the end.
A couple of simple demonstrations can help your students to see what dietary fibre is
like.
Show them samples of cellulose, pectin, and wheat bran in small beakers. Add a little
water to each and stir. Ask the students to describe the texture after adding water using
words such as gelatinous, gummy, absorbent or granular.
The strong attraction of dietary fibre for water determines the consistency and bulk of
faeces. You can demonstrate the water holding capacity of cellulose using wallpaper paste.
Add 100 ml water to about 10 g of cellulose granules in a beaker. Leave for a few minutes.
Go on adding more water to see how much the cellulose will bind to give a gelatinous,

semi-solid mixture. Alternatively, a laxative could be used, such as Fybogel, which can
absorb up to 40 times its own mass of water.
B3 Nutrition in plants and animals 27
Answer to question
Opportunities for co-ordination
There is a link with the study of gels in Chemistry.
Other resources
NCS Biology Chapter B6.
Pathways Sourcebook Bodywise pages 28-29 gives information about fibre in the diet.
Further information
Adamczyk, P., Willson, M. and Williams, D. School Science Review, (1994) 76 (275)
pages 116-124 gives an explanation of concept maps.

Nuffield Biology Section B4
Transport in plants and animals
Context
All organisms require transport systems. Diffusion is sufficient for the needs of smaller
organisms; larger organisms require more complex mechanisms. This section describes the
role of the heart, blood and blood vessels as an example of a more complex transport
system in mammals. The importance of water in both transport and support in plants is
examined experimentally.
B19 Looking at the heart
REQUIREMENTS
Each student will need:
activity sheets
The teacher may need:
heart (see note 1)
beaker large enough to contain heart
dish or tray
blunt forceps
scalpel (see note 2)
ruler
scissors
seeker
model heart
gloves
Access to:
plastic bag for waste material (see note 3)
top-pan balance
sink, soap, water and disposable towels
Notes:
1 You must obtain the heart from a butcher or other food shop since the carcase will then
have been inspected at the abattoir by the local health authority. You can use a frozen heart
but such material often lacks the main blood vessels. You can usually get a complete and
unfrozen heart if you explain what you need in advance.
You need to be alert to the religious, moral and cultural sensitivities in the class when
handling material from dead animals. For those who object to seeing, or handling organs
from dead animals for moral, cultural or religious reasons an alternative must be available.
Tell the class in advance that you will be showing them animal organs so that those who
prefer to can come prepared to work with the alternative. Suitable alternatives are models,
videos and illustrated textbooks.
2 Warn students not to look over other dissections while students are working with sharp
scalpels.
3 You should dispose of the heart quickly by incineration. Alternatively, you should wrap
it up and place it in a dustbin or container used for food wastes which will not be fed to
animals.

Answers to questions
Question 1 and 2 refer to the coronary arteries and link up with Activity B21. Students may
not have realized that heart muscle cannot rely on the blood in the heart chambers, so it
must have its own supply.
Question 3 requires an understanding of the low pressure of venous blood returning to
the atria.
Questions 4, 5, and 6 relate to the extra thickness of the wall of the left ventricle with
the need for greater pressure in the aorta than in the pulmonary artery.
Questions 7 and 9 emphasize the need for valves to maintain a one-way flow, when the
pressure ahead of the valve is momentarily higher than the pressure behind.
Question 10 allows students to consider how biological materials are suited for their
functions. Collagen is also the protein in bone, and in connective tissue. Vitamin C is
needed for its manufacture. Vitamin C deficiency results in scurvy.
B4 Transport in plants and animals 29
B20 What does the heart do?
REQUIREMENTS
model heart
video
computer program (see Further information about human physiology)
Notes on the activity
This activity should help students to understand the importance of the heart for raising the
pressure of the blood after it has fallen in the capillaries.
Students working at the higher level should appreciate that the heart is in fact two
pumps working together in a double circulatory system.
Extension work could include comparison with the single circulatory system of a fish,
and an attempt to explain the difference.
Opportunities for co-ordination
P16 'Measuring work' and P17 'Hard work and personal power' calculate the energy
transfers during physical exercise.
PI 1 'Camels' feet and sharks' teeth' uses pressure = force/area.
Other resources
NCS Biology Chapter B8.
B21 What happens if you have a heart attack?
REQUIREMENTS
Each student will need:
activity sheet
reference books
leaflets on healthy living, e.g. from health centres
first-aid manuals
This activity is suitable for private study or homework.
Answers to questions
1 Factors which make it more likely that someone will have a heart attack include:
being overweight,
not taking enough exercise,

30 B4 Transport in plants and animals
a diet high in saturated fats,
being a smoker - this is a significant factor,
a family history of heart disease.
2 If you think someone is having a heart attack you should
make the casualty comfortable, in a half-sitting position, with a cushion under the
knees and behind the back,
dial 999,
if the casualty is conscious, give one ordinary asprin to chew,
check the pulse and breathing and be ready to resuscitate.
3 Factors which make it less likely that someone
will have a heart attack include:
taking plenty of exercise,
being the correct weight for your height,
not eating too much saturated fat,
eating plenty of fibre,
not smoking - this is a significant factor.
4 Eating food high in saturated fat tends to raise
blood cholesterol levels. Cholesterol is a fatty
substance which coats the insides of blood vessels,
'furring' them up and eventually blocking them.
almost normal
coronary artery
5 The agonizing pain comes when the heart muscle is starved of oxygen as the blood
supply is cut off.
patient feels
angina
heart
attack
6 Streptokinase, if given soon enough, can dissolve the material blocking the arteries.
7 Doctors pass a long tube called a catheter into the blood vessels around the heart. They
squirt a special dye down the tube and then take an X-ray.
8 One technique for clearing the blocked coronary arteries is called angioplasty. The doctors
insert a small thin balloon at the end of a long thin tube into a blood vessel in the patient's
arm. They work the end of the tube along to the blocked artery in the heart. They then blow
up the balloon. It widens the blood vessel.
Instead of a balloon at the end of the long tube, doctors can now use a fine diamond drill
bit to break up unwanted tissue which is causing a blockage.
Often surgeons have to treat patients by opening up the chest and operating on the heart
itself. In by-pass surgery, doctors cut a blood vessel from another part of the patient's body
(perhaps from a leg) and sew it alongside the blood vessel in the heart which has become
too narrow. The blood can then flow through the new tube and by-pass the narrow one.
artery wall
plaque
balloon deflated
balloon inflated
depressing plaque
blockage or
narrowing

B4 Transport in plants and animals 31
9 The natural pacemaker, in the right atrium, starts a wave of contraction through both
atria, causing them to squeeze blood into the ventricles. The contraction then spreads down
the septum between the two ventricles, and up the sides of the ventricles, causing blood to
be forced into the arteries.
An artificial pacemaker, powered by a battery, can be implanted in the thorax. It sends
small electrical pulses to the heart which stimulate it to contract at a regular rate.
Other resources
Pathways Sourcebook Bodywise pages 14-15 gives information about heart attacks.
Further information
First Aid Manual (St John Ambulance, St Andrew's Ambulance Association, British Red
Cross) published by Dorling Kindersley
B22 Blood and blood transfusions
REQUIREMENTS
information on blood groups and transfusion compatibility
Students will need:
activity sheet
test-tube rack
means of labelling test-tube
distilled water
2 x 1 ml syringes
measuring cylinder, 10ml
container to act as water bath or communal water bath (if individual water baths then
usual heating apparatus and thermometers)
20 ml 'blood' (made up from Marvel, use 12 g in 100 ml water, to which saturated
Congo red aqueous solution has been added until 'blood colour', label this 'blood')
5 ml of rennin extract (available from chemists or supermarkets), label this
'blood clotter'
2 Petri dish bottoms
goggles
Safety note
Take care with syringes.
Take care with blood clotter as it is an enzyme, but do not mention enzyme on pupils sheet
Avoid glass shattering when tipping contents on to dishes
Care should be taken to avoid getting Congo red on the skin.
Notes on the activity
The main activity is Foundation level, and higher in the two discussion parts. The
experiment demonstrates the clotting of blood, using the clotting of milk as a model. Some
knowledge of blood structure would be useful.
The recomended way into the transfusion aspect of this activity is to show a clip from
the video The Blood Donor' by Tony Hancock, a BBC video. It is old, it is black and
white, but still manages to raise a smile.
Another way into this activity could be to read to the pupils the following account of
Arthur Coga's blood transfusion (from The Faber book of science, Faber & Faber, 1995).
One of the first blood transfusions into a human being was on 23 November 1667. The
Royal Society tried to get 'some mad person for the event' but the keepers of the mental
hospitals would not allow it.
A student from Cambridge, Arthur Coga volunteered. This is a report of the event.

32 B4 Transport in plants and animals
'the blood of a young sheep, to the quantity of about 8 or 9 ounces by conjecture, was
transmitted into the great vein of the right arm, after the man had let out some 6 or 7
ounces of his own blood. All of which was done by the method of Dr King's, which I
published in Num. 20 of the Transactions, without any change at all of it, save only the
shape of one of the silver pipes for more conveniency. Having let out, before the
transfusion, into a porringer, so much of the sheep's blood, as would run out in a minute
(which amounted to 12 ounces) to direct us as to the quantity to be transfused into the man,
he, when he saw that florid arterial blood in the porringer, was so well pleased with it, that
he took some of it upon a knife, and tasted it, and finding it of a good relish, he went the
more couragiously to its transmission into his veins, taking a cup or two of sack before,
and a glass of wormwood wine and a pipe of tobacco after the operation.'
Apparently Coga survived unharmed, was given twenty shillings, and went on to have
another blood transfusion, again surviving it. Other attempts were not so successful and
experimentation stopped until Landsteiner's discovery of the ABO blood groups in 1900.
Blood transfusion was first practised on a large scale in World War I.
There is a game called BUTTHEAD (see Further Information). This consists of a pair
of 'hats' worn by pupils with velcro strips on them. Three large soft balls are thrown at the
hats with object of making them stick on the velcro strips. With some modification this
could be used to show the blood groups. No doubt the pupils would enjoy this.
In order to discuss the importance of group O, pupils will need to make reference to a
text which has details of blood groups, what transfusions can be made and the relative
frequencies of blood groups within the population.You may care to widen the discussion
into the importance of using O rhesus negative (factor D).
Some additions to the list of blood parts mentioned in the article are:
immunoglobulins,
clotting factor products, e.g. factors 8 and 9,
white cells.
About 25 000 donations a week (450 ml x 25 000) are processed at Blood Centres. The
plasma is sent to the Bio Products Laboratory where immunoglobulins, albumin and
clotting factors are produced. The guide to preparation, use and quality assurance of blood
components is a useful reference for this part.
The last discussion point will become increasingly important and a good source of
background information is the Independent article mentioned in the reference material. As
well as the payment for the treatment there is the point about the donor who has given their
blood freely for treatments. Hospitals are not charged for the blood they receive; however,
they do pay a charge to cover the costs of collecting, testing, storing, and transporting the
donated blood. You could discuss whether blood donors should be paid if their blood is sold
to hospitals rather than being given freely as it is now. A useful extension of this area of
blood economics could be to look at the 'leaky blood bags' controversy of 1995.
Answer to selected question
3 As pupils are unlikely to have met rennin, it is hoped that they will suggest it is a
blood clotting factor which causes the blood cells to clump together. If they suggest it is an
enzyme, then you will need to tell them about the use of models to demonstrate life
processes.
Facts about the National Blood Service
An adult has between 4 and 6 litres of blood (just over a gallon) depending on body
mass.
In England we collect about 2.4 million units of blood every year.
A unit is 450 ml (just under a pint).
Every unit is tested to check its blood group and to make sure it is free from infectious
diseases.
This blood is collected from 1.9 million donors who give blood between 1 and 3 times
each year. The safe donation frequency is normally every 16 weeks. There are now nearly
100 donors who have donated over 100 units of blood and several have reached 150 whole
blood donations.

The blood is collected at approximately 19 000 blood donor sessions which could be at a
mobile session in a local hall or at your place of work, a permanent static clinic or in one
of the special bloodmobiles.
The National Blood Service provides blood and blood products to each of the 385
hospitals in England from one of the fourteen blood centres which are open 24 hours per
day, 365 days per year.
The blood will be used to help 800 000 patients each year. It will enable some patients
to have routine operations; others will need blood urgently to save their lives.
We need nearly 10 000 units each day to supply the hospitals' demand.
This demand is growing at the rate of 3 to 4 % each year.
This means we need an extra 80 000 to 100 000 new donors each year to keep up.
Over 90% of the blood is processed and divided into its components: red cells, white
cells, platelets and plasma. Very little whole blood is now used and a single donation can
help up to six different patients.
Red cells have a shelf life of 35 days and platelets only last for 5 days so there is a
constant need for more blood and we can't stock pile it.
New blood donors should be aged between 18 and 60 and be reasonably fit and healthy.
Other resources
NCS Biology Chapter B8.
Pathways Sourcebook Bodywise page 16 gives information about blood groups and blood
donation.
Further information
Butthead 1/2 Dawes Court, High Street, Esher, Surrey KT10 9QD
Guide to the preparation, use and quality assurance of blood components, Council of
Europe Press, 1995, ISBN 92 871 2687 9 available from HMSO
Carey, J., (ed) The FaberBook of Science, Faber and Faber, 1995, ISBN 0 571 16352 1
Hagen Piet J., Blood transfusion in Europe: a 'white paper', Council of Europe Press,
1993, ISBN 92 871 23772
Toynbee, P., 'Did the NHS cheat Jaymee' The Independent 27 October 1995, page 23
The Blood Donor' from The Very Best of Hancock' BBC Video V 5343
National Blood Service, Oak House, Reeds Crescent, Watford, Herts WD1 1QH.
B23 Looking at diffusion (H)
REQUIREMENTS
Each group of students will need:
agar jelly, cubes with sides 2 cm long, made with agar which has been stained dark blue
with 0.1 % DCPIP (allow pupils to cut their own cubes - see Notes)
vitamin C solution (0.1%)
2 beakers
filter paper or blotting-paper
rulers
scalpel
white tile
Access to:
water for washing cubes
Notes:
Agar is most easily prepared by purchasing tablets, adding water as directed and heating in a
pressure cooker. Add DCPIP to give a dark blue colour. The liquid is then poured into a
Petri dish and allowed to set. Larger blocks can be prepared by pouring the liquid to greater
depths in other dishes or beakers.
B4 Transport in plants and animals 33

34 B4 Transport in plants and animals
The agar should be prepared to a depth of 2 cm, so that pupils can cut their own cubes.
The questions, and the table, allow students to find out empirically that a large ratio of
area to volume allows the most rapid diffusion.
The extension questions should help students to realize that the demand for diffusing
molecules is proportional to the volume, while the supply depends on the surface area
through which the molecules can diffuse.
Safety note
The use of scalpels demands special vigilance.
ScO
1 c work quantitatively
On disc
Extra questions can be found on the disc.
B24 Water in and out of cells
Notes on the activity
This activity would be suitable for homework or private study.
Answers to questions
la and b The blood cells in distilled
water take in so much water that they burst
and there is nothing to see under a
if placed in water
the cell swells up
microscope.
When the cells are in 0.85 per cent
sodium chloride solution the water
concentration is about the same inside and
outside the cells. Overall, no water flows in
or out of the cells. The cells look normal
under a microscope.
red blood cell
In 3.0 per cent sodium chloride solution
cells lose water. Water is more concentrated
inside the cells than outside so it flows out
through the cell membrane. The cells shrink.
if placed in a strong salt
solution the cell shrinks
c Unlike plant cells, animal cells do not
have a strong cellulose wall. There is
nothing to stop too much water flowing into
the cell and bursting the cell membrane.
2 This question could lead to a discussion of the importance of the colon for
reabsorbing water which has been used in the digestion of food.
3 This question could lead to a more general review of food preservation by removing
water which is essential as a solvent for metabolism in all living cells, including the
microbes which spoil food. A high salt concentration also preserves food by osmosis.
Dried food has water removed by evaporation. In frozen food, the water forms ice crystals,
so liquid water is not available.
Opportunities for co-ordination
Question 2b gives an opportunity, with more able students, to compare solutions by
reference to their molarity.
and bursts
and crinkles

B25 Osmosis and turgor (H)
REQUIREMENTS
Students will need:
activity sheet
Skill sheet B1 - Using a microscope
red onions or rhubarb leaf stalks
forceps
microscope
2 microscope slides
2 cover slips
2 dropping pipettes
Access to:
concentrated sugar solution (2.0 mol/litre)
distilled water
filter paper
B4 Transport in plants and animals 35
Notes on the activity
The observation with red onion or rhubarb cells is reliable and gives good results.
Answers to questions
cellulose wall
cell
membrane
The student should see a regular structure of cells nucleus
when looking at the red onion or rhubarb tissue
mounted in distilled water. The vacuoles are filled vacuole
with red cell sap. It may be difficult to see the living
material (cytoplasm) around the walls of the cells. It
may also be hard to spot any nuclei.
When students examine the cells mounted in sugar
solution they will see that the cell vacuoles shrink. cytoplasm
The red colour seems to darken and concentrate near vacuole
the middle of the cells as the cytoplasm comes away
from the cell walls. When they replace the sugar
solution with distilled water they can see the
vacuoles filling up again and swelling to fill the
cells.
1 Water passes in and out through the walls of plant cells. The cytoplasm and cell sap of
plant cells contain sugars, salts and proteins. Put some cells in pure water and you find that
the water starts to move through the cell walls and cell membranes into the cells.
As more water passes into the cells the pressure builds up and the cytoplasm presses
outward on the cell walls. The cell walls are strong so they will not break. In time the
pressure builds up so much that no more water flows into the cells.
spaces filled with outside solution
cytoplasm
water out
water in
Plant cell in
distilled water
cell membrane
water in
water out
Plant cell in
sugar solution
non-living
cellulose
cell wall
living
cytoplasm
vacuole
(water and
various
nucleus
water outside
the cell
water diffuses
in both directions
but overall water
tends to flow
into the cell
pure water
(water more
concentrated)
o
•
o
solution of sugars
and salts in water
(waterless
concentrated)
_
O
water
molecules
O__larger
T/*" O • molecules
O • of dissolved
U O substance
part of a membrane hugely
magnified to show holes which
let small molecules through
2 Water flows from where it is more concentrated to where it is less concentrated.
3 When a plant is well watered there is plenty of water flowing up from the roots to the
leaves. All the cells in the stem and leaves swell with water. The pressure in all the cells
helps to keep the plant firm.

36 B4 Transport in plants and animals
When the plant is in dry soil there is not enough water flowing up from the roots to
replace losses by evaporation from the stomata in the leaves. There is then not enough
water to keep all the cells 'pumped up' so the leaves and stems get floppy. The plant wilts.
4 Plant cells in sunlight make more and more glucose. If all the glucose stayed in solution
the cell sap would get more and more concentrated. This would tend to draw water more and
more strongly into the cells and upset the flow of water from one cell to another through
stems and leaves.
Starch is insoluble in water. Making starch builds a store of energy food which does not
upset the water balances in the plant tissues.
Other resources
NCS Biology Chapter BIO.
B26 Active transport (H)
REQUIREMENTS
Each group of students will need:
graph paper
pencils
Notes on the activity
The procedure is detailed on the worksheet. There is some differentiation of questions on
this worksheet; teachers may find that some pupils need assistance when attempting the
more demanding problems.
Answers to questions
The rate of uptake of sulphate ions is faster in aerobic conditions, which suggests that the
presence of oxygen improves the ability of the seedlings to take up sulphate ions. As
oxygen is used in respiration, the process by which energy is made available, it is
reasonable to suggest that the data support the hypothesis that mineral uptake by plants is
an active process. However, the data for anaerobic conditions suggest that in this
experiment diffusion can account for the uptake of some of the sulphate ions.

B27 A summary of mass flow, diffusion and active transport (H)
Notes on the activity
This is another example of a concept map (see B18 for description and reference).
Answer to question
B4 Transport in plants and animals 37
All particles move
together at a
similar rate
^"^
Individua part cles
move n ndomly
^
from higher concentration
of those particles to a
lower concentration (down
their concentration gradient)
\ —•—.
Mass flow
e.g. movement
of air into lungs
------
\\
Diffusion
e.g. movement
of oxygen
molecules from
blood into cells
^^
Energy released by
respiration is needed
for movement of particles
/
from lower concentration
of those particles to a
higher concentration (up
a concentrat on gradient)
Osmosis
e.g. movement of
water molecules
from soil to root
hair cells
^\
Active transport
e.g. ammonium
ions from blood
to kidney tubules
A selectively permeable
membrane is essential
for this to happen
B28 Minerals for plant growth
REQUIREMENTS
Students will need:
activity sheet
Depending on their plans they may also need:
20 healthy Lemna plants of similar size
beakers or jam jars (one per culture solution)
plastic film to cover the beakers or jars, alternatively, Petri dishes with lids
or
about half a dozen healthy cereal seedlings germinated a week in advance (see note 1)
test-tubes (one per culture solution) in rack
cotton wool
aluminium foil or black card or black polythene to surround test-tubes
dropping pipette
or
algal culture solution (see note 2)
conical flasks (one per culture solution)
cotton wool
graduated syringe to dispense 1 cm3 portion
measuring cylinder, 100 cm3
microscope
microscope skill sheet
microscope slide
cover slip

38 B4 Transport in plants and animals
Access to:
a series of culture solutions, one complete, the others each lacking one nutrient (see note 3)
sticky labels
beaker with disinfectant to disinfect syringe
Notes:
1 You can germinate seeds on cotton wool or blotting paper in a margarine tub but the
problem is that the roots stick in the damp medium. It is then difficult to avoid tearing off
root hairs and roots when transplanting seedlings. It is a little more expensive but much
easier to germinate the seeds on wet OASIS foam or vermiculite.
2 A culture of Scenedesmus quadricaudus or Micrasterias thomasiana var. notata in
the complete medium (see note 3) and inoculated a week in advance. Chlorella may also be
used.
3 Tablets for making up the mineral salt solutions are available from biological
suppliers. The Long Ashton water culture reagent set provides a complete medium with
eight other formulations each lacking nitrogen, phosphorus, sulphur, calcium, potassium,
magnesium, iron or sodium. This set of reagents includes trace elements (copper, zinc,
manganese and boron).
4 Use a clear phenolic disinfectant at the manufacturer's recommended dilution. Suitable
ones are 'Cleansol', 'Hycolin', 'Pruntol', 'Stencol' and 'Sudol'.
Notes on the activity
Collaboration between groups will help to make the activity manageable given that all the
investigations need a large number of containers.
In bright light and under warm conditions, Lemna will give distinct results in a month
or two. Add an algicide to avoid the danger that the culture will be contaminated by algae. If
possible, use sterile glassware and boil the solutions before use (unless they are freshly
prepared). Replacing the culture solutions every few weeks helps.
Cereal seedlings show results in about three weeks. Take care not to wet the cotton
wool plugs when topping up the solution in the tubes.
The algal culture will give results soonest. We recommend Scenedesmus
quadricaudus or Micrasteria thomasiana var. notata because it looks attractive through a
microscope.
You can link this activity with the work on the nitrogen cycle and work on variation.
Rooted cuttings of Tradescantia could be used instead of seedlings. You could discuss
with students the advantage of these; since if they are all taken from the same plant, they
will be genetically identical.
Single seedlings may be genetically very different from one another - a good
opportunity to discuss fair testing!
The populations of algae are likely to have a similar genetic range, since the numbers
are so large.
Students working at the higher level will need to know the function of these nutrients,
and symptoms of deficiency, (especially nitrogen, phosphorus, potassium, magnesium).
They should also know that lack of one mineral will limit the rate of growth. This can
be linked with the study of limiting factors in photosynthesis (Bl 1). The 'green-ness' can
be conveniently measured in three ways.
1 Using shade cards produced by paint companies, with different intensities of colour to
make a comparison chart.
2 Using a colorimeter.
3 Measuring the turbidity by seeing what depth of algal culture is needed to obscure a
letter X drawn on a piece of card below the tube.

B4 Transport in plants and animals 39
Answers to questions
1 The pie chart shows the main elements that plants
need from the soil, or from the water solution in
which they grow.
All green plants need nine essential elements. The
six elements named in the pie chart come from the
soil. The other three elements (carbon, hydrogen and
oxygen) are taken in as carbon dioxide and water
during photosynthesis.
Plants also need minute amounts of other
elements which we call trace elements. These include
iron, boron, zinc, copper and manganese.
The elements are present in the soil as ionic
salts. Plants absorb nitrogen as nitrates, phosphorus
as phosphates and sulphur as sulphates.
ScO
1 c work quantitatively
sulphur
trace elements
The elements that plants need from the soil. This
pie chart shows the proportions of the most
important ones. Notice the tiny proportion of all
trace elements shown together.
Other resources
NCS Biology Chapter B15.
B29 Measuring the rate of water loss from leaves
REQUIREMENTS
Each group of students will need:
graph paper
pencils
Notes on the activity
Pupils are required to interpret data obtained from investigations with potometers.
Answers to questions
A complete interpretation would include a consideration of the diffusion of water molecules
from open stomata, and the effect of the atmosphere around the stomata.
Students should discuss the factors which increase the rate of evaporation in general.
They should also realize that light intensity is an additional factor in evaporation from
leaves, since it results in a change in size of the stomata.
Opportunities for co-ordination
There are links with changes of state in Physics.

40 B4 Transport in plants and animals
B30 Water from roots through leaves
REQUIREMENTS
Students will need:
activity sheet
Skill sheet B1 - Using a microscope
Busy Lizzie or celery stalk which has been standing in a blue dye for some time (see note 2)
sharp scalpel and white tile or dissection board
blue dye solution
0.5% eosin solution or food colouring
hand lens
microscope slide
cover slip
dropping pipette
Access to:
pot plants enclosed in plastic bag (see note 3)
thin section cut from stem which has stood in the dye solution (see note 4)
2 rooted Coleus cuttings set up as in part d on the activity sheet (see note 5)
microscope.
Notes:
1 Take Coleus cuttings 14 days
before the demonstration. Stand them in
water with liquid fertilizer to root. Rub
off any stray roots so that all the roots
are in the solution.
Support the cuttings in the plastic
containers. Put a 0.5% eosin solution in
one compartment and water or nothing
in the other compartment.
2 Busy Lizzie is easy to slice thinly.
Celery is difficult to cut neatly across for
sections. Stand some cut plant samples in
dye solution 12 to 24 hours before the
lesson. Others you can put in the dye at
the start of the lesson. Avoid skin contact
with the dye.
boxes glued together
cut down the dividing wall
a little way
— transparent plastic box
0.5% eosin
solution
Cole us cutting
plain water
Coleus cutting
0.5% eosin
solution
roots

3 Surround a pot plant with a plastic bag and stand on a bright window sill for an hour
or so. Later move to somewhere cooler to increase the condensation on the bag.
4 Suitable dyes are dilute methylene blue solution or a blue food dye. Cut thin slices
from a plant stem lying on a white tile. The thickness of the slices is not critical - aim for
about 1 mm and part of the section is bound to be thin enough. If you have a small pool of
water at the cut end of the stem, the slices will float on the water. Use a paint brush to
transfer the slices to microscope slides. Add a cover slip and make sure there is enough
water between the cover slip and the slide.
5 Coleus with lemon-coloured leaves works best. Make two containers for the
demonstration by sticking pairs of plastic indicator-paper boxes together. Then cut a little
way down the dividing wall.
Safety note
Care is needed when using scalpels. Avoid getting eosin on the skin. An alternative is food
colouring.
Notes on the activity
This activity may suggest ideas for further investigation and may spark off questions to test
in a Scl experiment.
The suggested answer for question 3 has an explanation for the observations in part (c).
Answers to questions
1 Students will soon see the inside of the bag turning cloudy. Water evaporating from the
leaves of the plant condenses on the inside of the bag.
Water flows into the roots of a plant from the soil, up its stem to the leaves where it
evaporates into the air. This evaporation of water is called transpiration.
2 Students will see that the dye is not , ,. . , . , ....
.j; , xylem-this is where the dye will be
spread evenly across the stem. The dye
shows up the part of the stem which
carries water from the roots to the
leaves. The bundle of long thin tubes
which carry water is called xylem. Here
is a drawing of a thin section of celery
stalk through a microscope.
B4 Transport in plants and animals 41
Section of celery stalk
(x15)
3 This investigation is to see whether particular leaves have their own water-carrying
tubes which reach from the tips of the roots to the leaves. In the cutting with half its roots
in water and the other half in dye solution, some leaves show dye in their veins while
others do not. This indicates that particular leaves are supplied by particular water-carrying
tubes. In the other cutting, where one set of roots was left in air, the dye appears in the
veins of all the leaves, indicating that the water tubes are interconnected and that water can
be transferred between them when the need arises.
Other resources
NCS Biology Chapter B8.

Nuffield Biology Section B5
Respiration
(Illustrated by humans as organisms)
Context
Respiration is a basic life process for transferring energy from food to the cells of an
organism. The process is inefficient and much of this energy is transferred to the
environment as heat. Human skeletal muscles can respire aerobically or anaerobically and an
understanding of this can influence athletic training and performance.
B31 Where does air go when you breathe in?
REQUIREMENTS
Each student will need:
activity sheet
diagram sheet
The teacher may need some or all of:
sheep or pig 'pluck' (see note 1)
large sheet of plastic or a plastic tray
scissors
plastic tube about 50 cm long
foot or hand pump (see note 2)
disposable plastic gloves
model to show the lungs and heart in a human thorax (see worksheet)
bucket as an alternative model, with the handle representing the ribs
Access to:
plastic waste bag (see note 3)
sink, soap, water and disposable towels
Safety notes
1 You must get the pluck from a butcher or other food shop since the carcase will then
have been inspected at the abattoir by the local health authority. Most butchers can provide
a pluck if given enough notice and you can keep it for a day or two in a refrigerator. A
pluck consists of the lungs, heart, trachea, larynx and parts of the diaphragm. Make sure
that the butcher does not leave the liver attached as it is not needed and can raise the price
considerably.
You need to be alert to the religious, moral and cultural sensitivities in the class when
handling material from dead animals. You may offer alternatives such as models and videos
for students who do not want to see you handling such material.
2 Do not attempt to blow into the tube yourself to inflate the lungs. Use a foot or hand
pump.
3 You should dispose of the pluck quickly by incineration. Alternatively, you should
wrap it up and place it in a dustbin or container used for food wastes which will not be fed
to animals.
4 Ensure that any students who handle the pluck wash their hands with soap and water.

B5 Respiration 43
Notes on the activity
See the introductory notes 'Using and teaching about living things' page 5. You can point
out the C-shaped rings of cartilage which keep the windpipe open and explain that the rings
are incomplete where the windpipe runs alongside the oesophagus. The larynx may also be
present. The diaphragm is made of inelastic collagen fibres, similar to tendons, with muscle
around the edge.
Arteries have thicker walls than veins and so appear less red. They contract when the
animal dies and look smaller than the veins.
The glandular tissue near the larynx is the thyroid gland. This gland produces the
hormone thyroxine which is important in the control of growth, development and body
metabolism.
You can inflate a lung using a foot or hand pump connected to a tube inserted into one
bronchus. Take care to blow and not to suck. The lung must not be inflated by a person
blowing into the lung.
You can take the opportunity to point out features of the heart. Show your students
that the walls of the atria are much less muscular than the walls of the ventricles. The atria
only have to pump blood into the ventricles. Note that butchers sometimes cut off the atria
so you may get a specimen with only the ventricles.
Make a point of washing your hands with soap and water after you have shown the
pluck.
If introduced sensitively, a pluck will arouse great interest. You can start by asking
students to identify the main features including the heart, lungs, windpipe, diaphragm, and
main blood vessels.
Opportunities for co-ordination
There are links with volume and pressure of gases, studied in Physics.
ScO
5 a take responsibility for recognizing hazards in a range of materials, activities and
environments, including the unfamiliar
B32 How you inflate your lungs
REQUIREMENTS FOR SIDE 1
Access to:
parallelogram model of human ribcage
syringe model of human thorax
Notes on the activity
The ribcage model can be used to illustrate
the movement of the intercostal muscles.
Note that the two sets of muscles are
antagonistic, and that contraction of one
set pulls the other set back to its original
length.
In the diagram, the band between P
and Q represents the external intercostal
muscles, which cause the ribs to move
upwards and outwards. A band stretched
between R and S would represent the
internal intercostal muscles, which cause
the ribs to move downwards and inwards.
Parallelogram model of the ribcage
sternum -
rib
backbone
elastic band
(represents the
external intercostal
muscles)

44 B5 Respiration
REQUIREMENTS FOR SIDE 2
Each group of students will need:
water
2 microscope slides
pipette
syringe model of human thorax
wood strips
Notes on the activity
The syringe model can be assembled as cover this hole plunger -push it
. } B , . , . „ n.ui
shown on the right. A finger over the hole
with your linger gently in and out
in the syringe casing will enable the
pressure in the barrel of the syringe to
change when the plunger is moved. The ___
plunger simulates the human diaphragm and **"7
the syringe barrel represents the thorax.
balloon held
Note that the balloon almost fills the tightly by bung barrel
syringe as do the lungs in the thorax.
The procedure is detailed on the worksheet. Syringe model of the thorax.
Answers to questions
Breathing in
• The external intercostal muscles contract.
• So the ribs are pulled upwards and outwards.
• The diaphragm muscles contract.
• So the diaphragm is pulled down.
• Both these movements increase the volume of the thorax.
• So the pressure in the thorax is reduced.
• Therefore air is forced from the atmosphere, into the lungs, where the pressure is lower.
Breathing out
• The external intercostal muscles relax.
• So the ribs are pulled down and in by the force of gravity.
• The diaphragm muscles relax.
• So the diaphragm is pushed up by the abdomen (whose pressure was increased during
breathing in).
• Both these movements decrease the volume of the thorax.
• So the pressure in the thorax increases.
• Therefore air is forced from the lungs, where the pressure is higher, out to the
atmosphere.
Opportunities for co-ordination
There are links with volume and pressure of gases, studied in Physics P14 'The spring of
air' includes Boyle's LawpV = constant, students examine the relationship between
pressure and volume of a gas.
ScO
Id judge when to use IT to collect, handle and investigate scientific information
Other resources
NCS Biology Chapter B7.
A stethograph could be used, Philip Harris produce one for use with their data loggers.

i
B5 Respiration 45
On disc
For students who need some help with the breathing sequences, there is a set of jumbled
sentences on the disc. These can either be copied in the correct order, or they can be cut and
glued.
B33 Understanding asthma
REQUIREMENTS
activity sheet
peak-flow meter
spare mouthpieces
disinfectant solution
(inhalers and nebulizers could be shown as examples of treatments)
Safety note
Students should be made aware of the need to clean the equipment properly before and after
use. No harm should occur with the use of a peak-flow meter although students should be
discouraged from repeatedly exhaling rapidly. Avoid the temptations to 'go for the class
record!' No student with asthma should feel obliged to take part unless they wish.
Notes on the activity
Students may enjoy collecting the data about asthma. It is a good opportunity for students
to discuss how to deal with a person who is suffering from an asthma attack.
^
400-
Peak 30° "
flow 200 -
1
reading ]QQ .
III 2
n -
3 4 5 6 7 8 9 10
M EM EM EM EM EM EM EM EM EM E
Peak flow chart (morning and evening)
in normal person over 10 day period
Readings were taken every
morning and evening for ten
days with a normal person, a
person with mild asthma and
a person with severe asthma.
The results were recorded
on peak flow charts as shown
below.
Peak 30° -
flow 200 -
reading
Peak flow chart (morning and evening) in
person with mild asthma over 10 day period
M EM EM EM EM EM EM EM EM EM E
Peak
flow
reading
Peak flow chart (morning and evening)
in person with severe asthma
M EM EM EM EM EM EM EM EM EM
Answers to questions
1 A bronchodilator relaxes the circular muscles in the walls of the bronchi and
bronchioles. So the tubes dilate, making it much easier to breathe, especially breathing out.
2 Allergic reactions cause inflammation and swelling (compare a wasp sting). The
swelling reduces the size of the airways. Intal prevents this response.
Opportunities for co-ordination
This activity can be related to Chemistry C14 Air pollution.

46 B5 Respiration
ScO
5 a take responsibility for recognizing hazards in a range of materials, activities and
environments, including the unfamiliar
Other resources
NCS Biology Chapter B7.
Pathways Sourcebook Bodywise pages 12-13 gives information about asthma.
Further information
Information about asthma can be obtained from:
Asthma Society and the Friends of Asthma Research Council, 300 Upper Street, London
Nl 2XX (they produce a leaflet on peak-flow measurement for a small charge)
Peak-Flow Meters are manufactured by:
Vitalograph Ltd, Maids Moreton House, Buckingham MK18 1SW
The Yoga Therapy Centre Tel: 0171 833 7267 offers information about relaxation
techniques for asthmatics (as an alternative to the use of drugs).
B34 Investigating respiration
Answers to questions
3 A small count is produced by background radiation and naturally-occurring carbon-14
in the air.
4 The carbon atoms in the glucose eaten by the rats become the carbon atoms in the
carbon dioxide they exhale. For this to happen the glucose molecule must have been
changed inside the rat.
Opportunities for co-ordination
P72 'Radiation from radioactive sources introduces radioativity for the first time.
P73 'Radiation dose: where does it come from?' introduces the idea of background
radiation. P74 'Half-life questions' (on disc) considers some of the uses of radioactivity in
medicine and tracing, including carbon-14.
C26 explains oxidation and reduction.
Other resources
NCS Biology Chapter B9.
B35 How much energy is there in some foods that you eat?
REQUIREMENTS
Each group of students will need:
activity sheet
foods, e.g. biscuits, dry pasta, cereals such as Shreddies, toast, olive oil on mineral wool
water, 100cm3
balance, accurate
boiling-tube
Bunsen burner
measuring cylinder, 100cm3
mounted needle
retort stand and clamp
thermometer, stirring
eye protection

B5 Respiration 47
Note:
It might be convenient to weigh the food before the practical starts; they can then be
provided in small Petri dishes with a note of the mass of each sample.
Safety
A student who is allergic to peanuts or other nuts may also have an allergic reaction to the
fumes produced by burning them. Check with the class as the incidence of peanut allergy
seems to be increasing.
Notes on the activity
The worksheet asks pupils to identify the major sources of error of the apparatus, to suggest
improvements and to evaluate other designs of calorimeters.
One way of collecting class results is to give each pupil a sticky label on which to
write results. Stick the labels onto a single sheet of paper and photocopy that sheet.
Answers to questions
1 This question focuses on heat lost to the surroundings, by conduction, convection
radiation and evaporation.
3 Approximate energy content per g:
Fat
37 kJ/g
Carbohydrate 16 kJ/g
Protein
17 kJ/g
Typical % composition of some suggested foods is:
digestive biscuit
pasta
olive oil
Fat
22
1
100
Carbohydrate
Digestible Fibre
67 3
74 3
0 0
Protein
7
11
0
4 and 5 These questions emphasize the similarity in end-products and energy released by
combustion and aerobic respiration.
6 The answer should focus on the controlled release of energy by respiration, at the rate it
is required and in a form which the cell can use.
7 The end product, lactic acid, is a relatively large molecule which therefore still contains
a large quantity of potential energy. So less energy is released but anaerobic respiration is
still useful as a short-term measure, e.g. in sprinters.
Opportunities for co-ordination
PI6 investigates the energy transferred from our food in various activities.
There is a link with combustion in chemistry, and with energy, including the energy in
molecular bonding. P65 'Heat electric' uses the idea of
energy transferred = 4.2 x mass (g) x temperature rise (in °C)
to measure the efficiency of electric heaters.
Students working at the higher level will realise that the 4.2 in the calculation refers to
the specific heat capacity of water, which is 4.2 J/g °C or 4200 J/kg °C.
Other resources
NCS Biology Chapter B6.

48 B5 Respiration
B36 Investigating cigarette smoke and its effects
REQUIREMENTS
The teacher will need:
Universal Indicator solution
chinagraph pencil
4 cigarettes
2 clamps, with stands and boss heads
2 conical flasks, with rubber bungs, each fitted with 2 bent glass tubes
cottonwool
dish for collecting ash from burning cigarette
filter pump
matches
rubber tubing, short lengths
T' piece, glass
2 hard-glass tubes, with bungs, fitted with tubes shaped to act as cigarette holders
Access to:
fume cupboard
balance
Notes on the activity
Note that there are commercially available kits which could be used as an alternative. In this
experiment it is worth comparing high and low tar cigarettes. The acid nature of cigarette
smoke can be investigated by bubbling it through Universal Indicator solution.
A graphic demonstration of the nature of cigarette smoke can be undertaken, using
Worksheet B36. The harmful effect of cigarette smoke on the health of individuals should
be discussed. Smoking also affects athletic performance, although this is often not
recognized by those athletes who are also smokers! Exercise affects the breathing rate. The
corollary of this is that if smoking reduces the efficiency of the lungs, then smokers must
find exercise more strenuous than comparable non-smokers.
Smokeless fuel has made Britain's cities clean. Imagine the difference that smokeless
cigarettes would make to Britain's lungs. Most of the damage caused by smoking is due to
harmful ingredients in the smoke - tar, carbon monoxide and nicotine. Cigarette smoke also
contains substances that irritate the lungs and increase the production of mucus (phlegm),
which is why smokers cough. Chemicals in the smoke may also gradually destroy the cilia
which reduce the likelihood of infection by sweeping away the phlegm. So in smokers
phlegm accumulates in the bronchi, which often become infected, causing bronchitis. Here
are some details about the things that cigarette smoke puts into the lungs.
Tar is a dark brown, sticky substance, which collects in the lungs as the smoke cools.
It contains carcinogens — chemical substances known to cause cancer.
Carbon monoxide is a gas that combines with haemoglobin, the oxygen-carrying
substance in the red blood cells, even more readily than oxygen does. So it reduces the
oxygen-carrying capacity of the blood by as much as 15% in heavy smokers. Unlike the
reaction with oxygen, the reaction is irreversible.
Nicotine is the addictive drug that makes smoking such a hard habit to give up. It is
also responsible for the yellow staining of a smoker's fingers and teeth.Nicotine can harm
the heart and blood vessels too - it makes the heart beat faster, the blood pressure rise and
the blood clot more easily.
Smoke from cigars and pipes contains more tar and nicotine than cigarette smoke, but
cigar and pipe smokers are less likely to get lung cancer.
ScO
5a take responsibility for recognizing hazards in a range of materials, activities and
environments, including the unfamiliar
Other resources
NCS Biology, Section B7.6.

B37 Smoking
B5 Respiration 49
REQUIREMENTS
Each student will need:
activity sheet
Access to:
leaflet, booklets and posters from anti-smoking organizations
Notes on the activity
Students are likely to have been on the receiving end of anti-smoking campaigns. This
activity gives them the chance to show how they would tackle the problem of persuading
young people not to smoke. In doing so, they consider the effects of tobacco on the way the
human body functions. As a preparative homework, they could be asked to collect health
warnings from cigarette advertisements and packages.
Some points that the students might think about:
• when and where children first feel the temptation to try a cigarette,
• whether or not children are influenced by advertising,
• how they have reacted to past anti-smoking campaigns.
The students should target ways of giving children information about smoking in
interesting and effective ways. What kinds of information are effective for the target agegroup?
What would students say to children who have already tried their first cigarette?
This work could be extended to produce a board game similar to the one in B45 (The
Nitrogen Cycle Game).
ScO
5 a take responsibility for recognizing hazards in a range of materials, activities and
environments, including the unfamiliar
Other resources
NCS Biology, Section B7.6
Pathways Sourcebook Bodywise page 13 gives information about smoking.

Nuffield Biology Section B6
Energy and nutrient transfer
Context
This section looks at the directional transfer of energy based on feeding relationships
between organisms/populations within food webs. The construction of pyramids allows
comparison of the efficiency of this process in different ecosystems. The importance of
mineral recycling and the role of decomposers is considered with regard to maintaining a
supply of minerals for plant growth. Good farming practice is explored with an emphasis
on maximizing crop production to provide food by increasing the efficiency of energy
transfer.
B38 Energy flows
Notes on the activity
This is quite a demanding activity which could be set as homework. It also raises some
interesting issues for discussion. It has links with the vegetarian diet mentioned in Activity
B8. Students working at the higher level need to understand why only some energy passes
from one trophic level to the next.
Answers to questions
1 Cattle maintain a steady body temperature. This takes energy so cattle respire more,
using up energy foods that might otherwise be used for growth.
The body temperature of an alligator goes up and down with the temperature of the
surroundings. In a hot climate, alligators stay warm enough for rapid growth without using
energy resources from the food they eat to control their body temperature.
2 and 3 Big animals, which kill and eat other animals, are near the top of food chains. The
diagram at the top of the activity sheet shows that the energy foods available get less and
less as you go up a chain from producers, to herbivores and then to carnivores. At the top
of the chain there is only enough food to support a few, large carnivores.
4 On average only 10% of an animal's food (with its potential energy) is converted into
body mass. So the rest is not available for use by animals at the next trophic level.
Other resources
NCS Biology Chapter B14.
B39 Food chains and food webs
REQUIREMENTS
activity sheet
plants and animals collected from fieldwork
reference books to help establish the animals' feeding methods
specimen dishes and trays
hand lenses
binocular microscopes

Safety note
Suitable precautions must be taken in all fieldwork, especially near water. (See
Introduction, page 2)
B6 Energy and nutrient transfer 51
Notes on the activity
Some students find the jump from food chains to food webs quite difficult. You will
probably have to remind them that, although food chains are neat and tidy, most animals
have several sources of food. Being a part of several food chains makes an organism less
dependent on particular food sources. It is one of the factors tending towards stability in
ecosystems.
When using the diagram on the activity sheet, students may find it easier to cut out
the organisms and re-arrange them on a sheet of plain paper, to find the clearest way to
show the food web.
Students may search for their own information about feeding relationships, or you
could provide the information below.
Producers - as well as the water crowfoot shown in the diagram algae should be
included.
A heron could be included, to eat the stickleback; also terrestrial insects which are
eaten by the pond-skater.
Detritus should also be included.
Stickleback - a carnivore which eats most of the small animals in the pond. Top of
the pond food-chains, but may itself be eaten by a heron.
Tadpole - a herbivore which eats green algae floating in the water and grazes on the
plants until it grows legs, when it becomes a carnivore and eats small pond animals.
Freshwater shrimp - eats the debris from dead remains of other creatures floating in
the water and at the bottom, also plankton.
Snail - a herbivore which eats leaves and stems of pond plants.
Mosquito larva - a herbivore which feeds on floating debris and algae in the pond
water.
Mayfly nymph - a herbivore which eats algae and plant debris.
Caddis fly larva - a herbivore which eats algae and plant debris.
Waterboatman - the greater waterboatman is a carnivore, it sucks blood from other
small animals.
Water louse - feeds on debris - the rotting remains of plants and animals at the bottom
of the pond.
Dragonfly nymph - a carnivore which eats most small organisms - several nymphs
can 'gang up' to attack a tadpole.
Pond skater - a carnivore which eats smaller terrestrial insects caught by surface
tension on the surface of the pond.
Other resources
NCS Biology Chapters B14, B16.
Pathways Sourcebook Environment pages 20-21 gives information about predation.
B40 Building pyramids of numbers
REQUIREMENTS
activity sheet
Notes on the activity
This follows on from Activity B38 and gives another opportunity to discuss how most
energy obtained by an organism is not passed on to the next trophic level. Students
working at the higher level need to know that most is in fact lost to the environment as
heat.

52 B6 Energy and nutrient transfer
sparrow
hawks
blue tits
caterpillars
cabbages
fleas
rabbits
grass
3 In a simple food chain we just show the names of the organisms at each stage. A
pyramid of numbers like the one on the activity sheets shows that as you go up the food
chain you often find fewer and fewer organisms. Here is another example:

B6 Energy and nutrient transfer 53
4a
Grassland
top carnivores
carnivores
herbivores
producers
Woodland
top carnivores
carnivores
herbivores
producers
b In the woodland the producers are the trees, each with a large number of leaves. Each
tree can support a very large population of herbivores.
Counting the trees in woodland and comparing them with the number of plants in
grassland is misleading (see Activity B41).
Other resources
NCS Biology Chapter B14.
Nuffield Science Calculations, topic 40 (Feeding relationships) gives some more problems
and examples.
B41 Building pyramids of biomass
REQUIREMENTS
Students will need:
activity sheet
squared paper
Notes on the activity
Ecological pyramids are quite difficult to draw. Students also find the idea of a pyramid of
biomass difficult. So this exercise requires some time and patience from everybody.
You might introduce the idea by asking students: 'How many grasshoppers do you need
to give the same mass as one sheep?' Sheep and grasshoppers are both herbivores and
appear at the same level in similar food chains. Pyramids of biomass showing food chains
involving these organisms would look very different from comparable pyramids of
numbers.
If the students are to come to grips with these basic ecological principles rather than
just learning how to draw the pyramids (just a tool in this activity) they need enough time
to reflect on what they have found out.
Answers to questions
carnivores
herbivores
producers
Eniwetok coral reef

54 B6 Energy and nutrient transfer
2 The scientists dry the organisms before weighing them so that they do not include
water. The proportion of water varies from one living organism to another. Measuring
biomass gives a better impression of the extent to which an organism grows as it takes in
energy and nutrients.
3 A pyramid of numbers can be misleading because each organism counts as one, no
matter how large or small it is. An oak tree and a grass plant count the same in a pyramid
of numbers.
Ecologists can overcome this problem by estimating the total mass of all the
organisms at each stage of a food chain.
4 There are seasonal variations in the amount of biomass in a woodland. In the autumn
trees lose their leaves, which then rot away. There is no food for caterpillars. Many insects
die, others survive as pupae. Birds migrate to other parts of the world.
In spring, buds open on the trees. Caterpillars start to feed on the leaves. Adult
butterflies breed to produce many more caterpillars. Birds return, build nests, breed and feed
their fast growing young.
Other resources
NCS Biology Chapter B14.
B42 Pesticides in food chains
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
The activity shows how an understanding of ecology can help us to think about problems
arising from human impacts on the environment.
Answers to questions
i
Cormorant 26.4 ppm Merganser 22.8 ppm
Tern 3.91 ppm
Heron 3.57 ppm
Sneepnead minnow 0.94 ppm
Plankton in river water (0.04 ppm)
2 The DOT is 800 times more concentrated in plankton than in river water. Plankton
float in water and easily absorb pesticides.
3 Here is one food chain from the web with the DDT concentration in parts per million
(ppm) under each name:
plankton
0.04 ppm
silverside minnow
0.23 ppm
pickerel
1.33 ppm
cormorant
26.4 ppm
With a persistent chemical, such as DDT, the concentration of the pesticide in body tissues
rises as you go up a food chain.

B6 Energy and nutrient transfer 55
4a
Animal
caterpillar
blue tit
hawk
Quantity of
pesticide
in the body / (ig
0.1
10
1000
Body mass / g
1
10
100
Concentration of
pesticide
in parts per million
(ppm)
0.1
1.0
10.0
b There is enough pesticide in the tissues of hawks to affect their breeding success.
5 The answers in question 4a assume that none of the pesticide breaks down and that
none is excreted by the caterpillars and birds. In reality birds and other animals do excrete
pesticides. Also pesticides do break down in living tissues, in water or in the soil.
The diagram shows possible pathways for a pesticide sprayed onto farmland.
excreted by animals back into the lake
decomposed by
micro-organisms
trapped in sediments
ScO
1 c work quantitatively
2 c relate scientific knowledge and understanding to the care of living things and of the
environment
Other resources
NCS Biology Chapter B17.
Pathways Sourcebook Environment pages 12-13, 18-19, 26-27, 36-37.
On disc
There is an extract from Silent Spring, by Rachel Carson on the disc, with further
questions.
B43 The carbon cycle
REQUIREMENTS
Students will need:
activity sheet
diagram sheet
textbook
paper glue (solvent free)
scissors

56 B6 Energy and nutrient transfer
Notes:
The set of 'cards' could be used as the
basis of a game. You might ask your
students to devise a game based on the
cards.
The 'ingredients' of the carbon cycle
included on the activity include all the
features which normally appear in
diagrams at this level. There are, however,
important omissions. The oceans have a
crucial part to play in determining the
level of carbon dioxide in the air.
With some students you might like to
introduce some of the concepts used by
environmental scientists including:
reservoirs, sinks and flows. Here is a
simple model of the carbon cycle which
includes the oceans. Putting some figures
to the cycle helps to keep in proportion
the impact of human activity.
Atmosphere
6.2x10 16 mol
,16''
0.77 xlO16 mol/year 0.75x10
mol/year
0.32 x10 16 mol/year
Surface oceans
8.3x10 16 mol
Deep oceans
317x10 16 mol
Ocean sediments
50x10 l6 mol
0.83 x 10' 6
mol/year
16 0.31x10
mol/year
^0.85 x10 1 mol/year
Biosphere
17x10 l6 mol
0.04 x10 16 mol/year
Fossil fuels
42x10 16 mol
Answers to questions
burning of plants
(including wood)
photosynthesis
respiration in plants
carbon in plant tissues (as carbohydrates,
proteins and other chemicals)
/
death of plants
L
carbon in the remains of
dead plants, including wood
decomposers feeding on the remains of dead
plants and animals
\ f
carbon dioxide in the air
herbivores feeding"
on plants
carbon in the remains of dead animals
carbon in the bodies of decomposers (as
carbohydrates, proteins, fats and other
chemicals)
respiration in animals
rv-V.i
carbon in the bodies of herbivores (as
carbohydrates, proteins, fats and other
./ excretion of urine and dropping^
death of animals dung by herbivores\
>
carnivores feeding on
other animals
decomposers feeding
on animal dung
carbon in animal urine and dung
carbon jn the bojjes- of^arnj vores (as
carbohydrates, proteins, fats and other
chemicals)
fossilization (over millions of years) of the
remains of living things
carbon in fossil fuels
"*" (coal, natural gas and oil)
burning of coal and oil
1 Large amounts of carbon are tied up in fossil fuels (coal, gas and oil). The fuels
formed very slowly over millions of years and, but for human activity, would remain

uried in the Earth for many more years. Extracting and burning fossil fuels very
quickly turns the 'trapped' carbon back into carbon dioxide in the air. Plants take carbon
dioxide from the air for photosynthesis. The carbon is then locked up as cellulose and
other chemicals in plant tissues. Wood is a large reservoir of carbon. Trees have a long
life so it can be many years before the carbon in wood returns to the air when wood
burns or rots. Destroying forests returns carbon to the air as carbon dioxide much more
quickly.
2 a A short circuit is a fault in an electrical circuit that allows the current to by-pass
the load. A short circuit may be an accidental connection between two parts of the
circuit providing an easier (low resistance) path for the current. A short circuit wastes
energy (by flattening batteries for example). A short circuit may be dangerous because it
can allow a large current to flow, damaging components in a circuit.
b Burning fossil fuels and wood provides a quick and easy way for carbon to get back
into the air as carbon dioxide. Burning fuels and wood uses up energy resources. Short
circuiting the carbon cycle in these ways may be dangerous if global warming upsets
the Earth's climate.
3 a Measurements at the Mauna Loa observatory in Hawaii show a steady rise in the
concentration of carbon dioxide in the atmosphere. Pictures of the Earth's surface from
satellites show how quickly the world's forests are disappearing.
b Adding carbon dioxide in the air helps to warm up the Earth by the greenhouse
effect. Many scientists think that global warming will lead to damaging climate changes
and a big enough rise in sea level to flood the low-lying lands where many people now
live.
Do plants and animals alter the environment around them?
This is a good opportunity to refer back to Activity B9, to illustrate the carbon
cycle as an example of the balance of nature.
Opportunities for co-ordination
CIS, students burn fuels, producing carbon dioxide.
C47 considers the origin of coal and oil.
C52 discusses the development of the Earth's atmosphere.
Other resources
NCS Biology Chapter B15.
B6 Energy and nutrient transfer 57
B44 The nitrogen cycle (H)
REQUIREMENTS
Students will need:
activity sheet
diagram sheet which they keep
This activity allows you to help your students to see how the various parts of the nitrogen
cycle are linked together.

58 B6 Energy and nutrient transfer
Answers to questions
/ \
/ nitrogen fixation^
denitrification I by bacteria in root
by soil bacteria I nodules and soil
*/ \bactena ^^
/OVxiX.,.-,. !,„„.„,:, SOil _^-
ammonia, monia, NHjjinthe^. NHginthe^. nitrates jtrates , in the
®Y^® bacteria J^^^—"
ftO chanae
Opportunities for co-ordination
C7 1 explains the Haber process.
Other resources
NCS Biology Chapter B15.
B45 the nitrogen cycle game (H)
REQUIREMENTS
students will need:
activity sheet
poppet beads
six-sided game die
This activity is an opportunity to review the nitrogen cycle in an entertaining way. The
design of the game board emphasizes the notion of a cycle.

Nuffield Biology Section B7
Health
Context
This section looks at the role of the body's defence systems in the prevention of infection.
It examines the effects of various drugs on different parts of the body and looks at the
problems associated with drug misuse.
B46 Body defences
REQUIREMENTS
Each student will need:
activity sheet (which may be cut up)
tracing paper or scissors
glue (solvent free)
Notes on the activity
This is a relatively simple activity which might be completed in private study or for
homework. Some students may find it a helpful way in to the more difficult tasks in
Activity B48.
Mucus in the windpipe traps microbes.
Protection by the blinking reflex and eyelashes,
microbes washed out by a watery fluid
Mucus, a sticky liquid, traps microbes
Coughing helps to move the mucus and microbes
out of the windpipe
Body has little chance if needle is not sterile
Unbroken, dry skin provides a covering to
prevent microbes getting in
Plaster covering cut
Blood forms a protective cover or scab.
White blood cells kill microbes in time
Acids kills most microbes
Poisons are removed by sickness and diarrhoea
The low pH of mucus in the vagina protects against some
infection. The normal population of bacteria in and around
the vagina may also give some protection
No real defence here, care especially in swimming pools

60 B7 Health
B47 How does a theory become an accepted fact?
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
The two diseases in this study are caused by bacteria, but the discussion could include
historical evidence for the existence of viruses, before they had been identified by using an
election microscope. You could also discuss the parallel improvements in social conditions
and medicine, both equally important in fighting disease. There may be a possibility of
links with the history department.
Answers to questions
1 Answers might include the vested interest of the older doctors and their resistance to
change.
2 Variables cannot always be controlled in a biological investigation as they can in
physics. If students have carried out an ecological investigation, they will realize the
problems caused by variation between organisms. But by studying thousands of families
supplied by each water company, and living in the same streets, Dr Snow could assume that
they each formed a similar cross-section of the whole population. Variables such as food,
shelter, family size, income, other diseases, could not be controlled but they probably had
the same range in each of the two samples. (You could compare this with the problems of
conducting a clinical trial on a new drug.)
3 Cholera bacteria damage the lining of the colon, so that water is not reabsorbed.
This is a chance to recap on the functions of the colon and kidneys, blood pressure,
osmosis and the reason why pure water could not be injected into the blood. Students may
know of babies who have become seriously ill as a result of dehydration caused by
diarrhoea. By treating the symptoms, patients are given time to make antibodies to destroy
the germs.
4 Louis Pasteur (1822-1895) had a wide-ranging career - testing the idea of spontaneous
generation, studying the optical activity of mirror-image molecules, identifying bacteria as
the cause of wine becoming sour and of a disease of silkworms and developing vaccines
against anthrax, chicken cholera and rabies.
References
Farrell, J. G., The Siege of Krishnapur, Weidenfeld and Nicolson, 1973
Weatherall, M., In Search of a Cure - A History of Pharmaceutical Discovery , Oxford
University Press, 1990
ScO
3 b consider ways in which scientific ideas may be affected by the social and historical
contexts in which they develop, and how these contexts may affect whether or not the ideas
are accepted
B48 Germs and you
REQUIREMENTS
Each group of students will need:
activity sheet
diagram sheet

B7 Health 61
Notes on the activity
This activity offers a way of finding out more about students' knowledge and understanding
of diseases and drugs at the start of the topic.
Decisions, decisions
Below are some typical scenes which the students may act out.
Scene 1 In the doctor's surgery
Here is what the doctor might want to explain to the young person and his parent:
'Often a sore throat is the first sign that you are getting a cold. Unfortunately we don't
have any ways of curing the common cold, which is caused by a virus. All you can do is
wait till you get better. You don't really need drugs.
For a sore throat, anything sucked or chewed helps your body to produce saliva, which
can ease the soreness. Drinking warm fluids can ease the pain too. Some people like a
soothing drink made with warm water, lemon juice and honey.
Bacteria can give you a sore throat too. I can't tell just by looking. We'd have to have
some tests done to find out. Then antibiotics would make you better.
I can't really say why you get more sore throats than your friends. Germs like warm
moist places to grow. Places where there is lots of food. But I can't see why they prefer
your body.'
Scene 2 At the clinic
Here is what the health visitor might want to tell the parents:
'We recommend that all babies should be immunized against diphtheria, tetanus,
whooping cough, polio and measles in the first fifteen months of their life. You may find
that your baby seems uncomfortable and unhappy for a few days after immunization. You
can be sure that it is well worth a little discomfort to make sure that your baby does not
catch diseases that can make a child very ill and maybe harm them for ever.
There would be an end to epidemics of all these dangerous diseases if we could get nine
out of ten babies immunized. There were some scares about whooping cough but we now
believe that it is right for nearly every baby to be immunized. Whooping cough makes
children very ill and can have very serious complications. The risks from the disease are
much more serious than the risks from immunization.
We only make an exception for babies which have already had an epileptic fit. We now
advise immunization even for babies who may have a close relative who is epileptic.'
Scene 3 At the pharmacy
Here is what the pharmacist might say to the customer:
'You need to understand the difference between a disease caused by bacteria and a disease
caused by a virus.
Antibiotics generally only attack bacteria - such as the bacteria which cause
pneumonia, sore throats and tuberculosis.
At the moment there is very little that drugs can do to cure diseases caused by most
viruses - such as colds, chickenpox, and polio. Often a doctor can only give you a
painkiller to make you feel a bit better while your body fights the disease. Immunization is
our main weapon against viral diseases.
Viruses can only multiply inside the cells of the infected animal (or plant). They
change the way the infected cells work so that they make more of the virus. Eventually the
infected cells die, burst and release hundreds of copies of the virus to spread the infection.
This makes it hard for drugs to get at viruses because they are hidden inside the cells of the
infected organism.
Doctors do sometimes give antibiotics to people with viral diseases, not to fight the
virus, but to protect them from other (secondary) infections while their resistance is low.'
Scene 4 At the bedside
Here is what the sick person might say to the visitor:

62 B7 Health
'Of course medicines contain drugs - that's why I take them. Sometimes medicines can
actually help to cure the disease. Sometimes they just make me feel better while I get over
the disease.
I know that there is no cure for this cold I've got. Painkillers make life bearable while
I'm getting better. I find that cough mixtures help even if some doctors say that they don't
do any good.
I have talked to my doctor and got some advice. She says that I should try and avoid
mixing drugs or taking medicines which have lots of active ingredients. She also says that I
will get better anyway in a few days.
I realize that medicines have side effects. Look at the labels on these packets. If they
warn about drowsiness I don't take the medicine before driving. I never get constipation so I
don't need to worry about that. Anyway, you can't buy medicines with more severe side
effects. You have to get your doctor to prescribe medicines like that.
Why should you worry! You drink and smoke. Alcohol and nicotine are powerful drugs
which will do a lot more harm to your body than these medicines ever do to me. So don't
nag on about my pills and potions.'
Types of disease - HIV and AIDS
When students make their list of infectious diseases, this will almost certainly include
AIDS. To realize why AIDS kills, students will need to understand how the immune
system makes antibodies.
Below is some information about HIV and AIDS which could be used as the basis of a
discussion. In a state school HIV and STDs should only be taught within the guidelines of
the school's sex education policy as approved by the governors and in accordance with the
information sent to parents. HIV and STDs are expressly removed from the Science
National Curriculum. For full guidance contact the DfEE.
1 HIV stands for Human Immunodeficiency Virus. AIDS stands for Acquired Immune
Deficiency Syndrome. A person with AIDS is no longer able to make antibodies against
infectious diseases. This is why they may die of a disease such as pneumonia, which most
people would easily recover from with the help of medicines. People infected with HIV
nearly always develop AIDS. It sometimes takes years. During this time they can feel
perfectly healthy but they are infectious. They can pass HIV on to others in the ways
described below even when they themselves are feeling well.
2 HIV can be passed through unprotected intercourse with an HIV infected person. Sexual
intercourse may be vaginal, anal or oral. You can also be infected by sharing a needle with
an HIV infected person. An HIV infected mother can pass on the disease to her baby either
before birth or possibly after birth through her milk.
3 HIV is hard to get and easily avoided. There is still no cure, so preventing AIDS means
that people must protect themselves against HIV infection.
HIV is spread by sexual intercourse. Avoid HIV by being faithful to a partner who is
free of infection and faithful to you. Avoid infection by using a condom correctly during
intercourse.
HIV is spread by injections with unsterilized, shared needles. Those who inject drugs,
for whatever reason, should not share syringes or needles with anyone.
4 AIDS is often in the news because it is a 'new' disease. Doctors first identified AIDS
in the early 1980s. Some people think that it could have existed for 30 years before that.
The number of people infected with HIV is rapidly increasing all over the world and there is
no cure for AIDS. People are interested in the results of any new treatments.
5 The delay between HIV infection and developing AIDS creates worry and uncertainty.
At the moment there is no cure for AIDS. Drugs can only slow down the course of the
disease.
6 You can only tell if someone has been infected with HIV by testing to see if the person
has the antibodies to HIV in their blood.
7 The ease of modern travel allows people to move around from country to country faster
and more frequently. New types of contraception, such as the pill, changed some people's
attitude to sexual relationships. People who are HIV positive may feel and look perfectly
healthy and yet be able to pass on the virus to others through sexual intercourse.
The cartoon sheet which follows could be copied for students to discuss and then write
an account in their own words.

B7 Health 63
AIDS is a disorder of the immune system and attacks the cells which produce
antibodies to the disease.
In people who are not infected with HIV, the appearance of a foreign microbe in the
blood triggers off the production of antibodies specific to the germ. These inactivate the
germ.
The first four frames of the cartoon strip show white cells responding to a flu infection.
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In HIV infected people, the virus enters the T4 cell forcing it to make more of the
virus. The B cells make only a small amount of antibodies. These can be detected in the
blood but are not enough to deal with the virus. The virus multiplies affecting more and
more T4 cells. The T4 cells burst releasing more and more of the virus and affecting more
and more T4 cells.
The body's immune system is damaged. Invasion by microbes which would normally
be made harmless by the white cells causes serious illnesses often leading to death.
The last six frames of the cartoon strip show why infection with HIV breaks down the
immune system.
Answers to questions
1 Vaccines protect people from diseases caused by microbes such as bacteria and viruses.
2 Vaccines are very important because they can stop people getting diseases for which
there is no cure. Preventing disease by vaccination is much cheaper than medical treatments
for people when they are ill.
3 The first vaccines came from cows. Vacca is the Latin for cow.
4 When a person catches a disease such as measles, the body fights it off, producing
antibodies. These antibodies remain in the blood even after the person has recovered. Next
time the person is infected with the measles virus there are antibodies already in the blood.
The antibodies soon make the virus harmless and the person does not get ill. The person is
immune to measles.

64 B7 Health
A vaccine is a special form of a virus or bacteria that causes disease. The microbes have
been changed enough to stop people getting ill. They are, however, still similar enough to
the original microbes for the body to make lots of antibodies.
Dead or weakened microbes still alert the body to produce antibodies but they do not
cause the person to catch the disease and become ill. There are three main types:
• Some vaccines contain microbes that have been changed and made harmless, such as
smallpox, TB and polio vaccines.
• Some vaccines contain microbes that have been killed, such as the cholera, typhoid, flu
and whooping cough vaccines.
• Some vaccines contain toxins that have been altered to make them harmless, such as
tetanus and diphtheria vaccines.
Vaccines give a person immunity to a disease -just as if the person had had the disease
and recovered from it.
5 A worldwide vaccination campaign has wiped out smallpox. Specimens of the virus are
still kept in laboratories (rather like endangered species in zoos).
6 The World Health Organization is hoping to wipe out six killer diseases: measles, TB,
diphtheria, tetanus, whooping cough and polio.
7 Medical scientists do not understand fully the causes of cancer. There are anyway a
variety of causes including ultra-violet light, ionizing radiations, some chemicals, asbestos
and smoking. None of these involve microbes and so vaccination is not possible.
It may be that viruses trigger some types of cancer but until this is better understood it
will not be possible for scientists to develop vaccines to prevent these forms of the disease.
8 There are different types of flu virus. Catching one type of flu means that a person has
antibodies specific to that virus and won't catch that type of flu again. Another flu virus can
still give a person flu. People are only immune to the flu virus they have already been
exposed to (by catching the disease or by vaccination).
Each year the scientists who plan vaccinations have to decide which forms of the flu
virus are likely to affect most people in the coming winter. They make vaccines for a few
of the forms of the virus that seem to be the biggest problem that year.
Note:
During the holiday season, this activity might be linked to a review of the advice now
given to travellers about vaccinations and other means of avoiding infection. See Further
information about health, page 140.
ScO
2 a consider ways in which science is applied and used, and to evaluate the benefits and
drawbacks of scientific and technological developments for individuals, communities and
environments.
Other resources
NCS Biology Chapter B3.
Pathways Sourcebook Body-wise pages 34-35 gives information about vaccinations.
B49 Alcohol
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
This activity looks mainly at the relationship between alcohol and road accidents, but it
could lead to a wider study of some other effects of alcohol on both the drinker and on their
family and friends.
There may be students whose parents are alcoholics so sensitive handling of the topic
is needed.

B7 Health 65
The difference needs to be stressed between a legal alcohol limit for drivers and a safe
limit. Statements such as '5 units of alcohol brings an average man to the legal limit' can
be misleading. Even one unit would greatly increase the accident risk to an inexperienced
drinker - especially one who is also an inexperienced driver whose body mass is below
average. There are also many metabolic variables, inherited and acquired.
Role play might be used to illustrate the reactions of the driver, police, families and
friends, following an accident.
The Department of Transport's Campaign against drinking and driving has been very
successful. The number of people killed in drink-drive accidents has fallen from 1650 in
1979 to 510 in 1994. But that still means ten people dying every week in drink-drive
accidents. And nearly half of these were not drinking themselves.
Opportunities for co-ordination
P88 'Motorway madness' deals with thinking distances and road safety.
ScO
5 a take responsibility for recognizing hazards in a range of materials, activities and
environments, including the unfamiliar
Other resources
NCS Biology Chapter Bl 1.
Pathways Sourcebook Body wise page 17 gives information about drinking and driving.
Further information
Information on drinking and driving is available from the Royal Society for the Prevention
of Accidents (RoSPA) Cannon House, The Priory Queensway, Birmingham B4 6BS.
Alcoholics Anonymous can be contacted at PO Box 1, Stonebow House, Stonebow, York
YO1 2NJ. Their local helpline number is in your local telephone book.

Nuffield Biology Section B8
The nervous system and hormones
Context
This section looks at how organisms respond to changes in both their external and internal
environments. It covers the reception of stimuli and co-ordination of responses which
make complex activity such as sport possible. Students are likely to be familiar with the
effects of eye defects, giddiness and temporary hearing loss which are relevant to this topic.
The section also covers hormone therapy and important commercial applications of plant
hormones.
B50 Stimulus and response
REQUIREMENTS
Students will need:
activity sheets (sides 1-4)
Side 2
pen
sticking plaster with pattern of holes (see activity sheet)
bristle
cork
disinfected hair pin
blindfold
Side 3
torch
Side 4
Either
computer
reaction timer software
or
scale (copy from diagram on next page)
stopwatch
Safety note
Only the blunt end of pins should be used. Each student should be in charge of their own
sterilized pin, which another student will use to test them.
Notes on the activity
Using students as the objects of investigation needs very careful consideration and care.
There should be no compulsion to carry out this activity.
You might organize the activities as a circus or you might arrange for each group to
concentrate on one activity and then 'report back' to the whole class. Side 1 has prompts for
each activity suggesting investigations. Some students might compare the computer
method for measuring reaction times with the ruler method as a study of experimental
uncertainty.

B8 The nervous system and hormones 67
—— cr —
— 21 —
20—
———— .20 s -— 19 —
- 29s —— 40
39-
18—
————.19s —— 17—
16—
- 28s———37-
10 -
— 15 —
—14—
-27s———35—
26-
13-
34—
———— .16s —
12
————.15s—— 11 —
-26s———32-
10—
— 9~
-25s——30-
p
29-
————.12s—— 7 —
n r
— 6 —
-24s —— 27-
38-
36-
33-
31-
28-
. IU S
no -
— 5 —
— 4_
-23s———25-
24 -I
— 3 —
———.07s ——
——— .06 s ——— 2 —
Join the strips end to end
exactly on these cut marks.
-.22s———23H
— 1 —

68 B8 The nervous system and hormones
Answers to questions
Receptors in the skin: (side 2)
Some parts of the body are much more
sensitive to touch than others. The distorted
diagram of a man shows how sensitive
different areas of a human's skin are to
touch.
The table includes typical results from a
'one touch or two' investigation.
Region of skin
Tip of tongue
Palm side of finger tip
Red parts of lips
Tip of nose
Palm of hand
Heel
Back of hand
Forearm
Middle of back, upper arm, thigh
Least distance
points to feel
touches / mm
1.1
2.3
4.4
6.6
11.3
22.0
31.6
39.6
67.0
between
two
Reflex responses (side 3)
Reflex responses are automatic. We make them without thinking. Our bodies respond to
many changes in our surroundings without thought. Breathing, swallowing, shivering and
sweating all happen in this way. This diagram shows the pathway for the nerve impulses
for a reflex response to pain. A sense organ in the skin responds to the hot object. This sets
off a nerve impulse to the spinal cord. Connections in the spinal cord relay the impulse to a
nerve which stimulates muscles in the arm to contract, pulling the hand away from danger.
By the time the brain registers pain the hand has been withdrawn.
cell body of
spinal nerve
relay neurone
cell body of
sensory neurone
cell body of
motor neurone
spinal cord
message from motor neurone
makes muscle contract
hand touches hotplate
This can be drawn as a flow diagram.
Intense
heat
Pain receptor
in skin is
stimulated
impulses
along
sensory
nerve
Central
nervous
system
impulses
along
motor
nerve
Biceps
muscle
contracts
Arm bends,
pulling hand
away from
hot plate

B8 The nervous system and hormones 69
When studying the pupil reflex students will see that the subject's
pupils get smaller when the tester switches on the light. The size of the
pupil is controlled by muscles in the coloured iris. Note that when
light shines on only one eye, the pupil of the other eye shrinks too.
This is used by doctors when checking for brain damage, in which
case the pupils may not both change diameter together.
.228
of a
sec.
If you can't do
better than this -
be very, very
careful on the road
Reaction times (side 4)
Here is part of a card for testing reaction times produced by the Royal
Society for the prevention of Accidents. Alcohol and other drugs can
affect reaction times making it much more likely that a driver (or
someone working with machinery) will have an accident.
The reaction time for a reflex is the time taken for a nerve impulse
to travel from a sense organ to the spinal cord or brain and back to the
muscles.
In this activity the response to a squeeze on the shoulder is not an
automatic reflex response. Students have to make a conscious reaction
to feeling a squeeze on their shoulder and then act by squeezing their
neighbour's shoulder. They should find that practice will help the group
to cut down the time it takes for the signal to travel round the circle.
ScO
Id judge when to use IT to collect, handle and investigate scientific information
Other resources
NCS Biology Chapter Bl 1.
.217 Daydreaming?
.204
.191
.161
.144
Still too slow! I'm
not taking a lift in
your car
Not bad at all -
carry on practising
Good! You should
have no difficulty in
.177 braking quickly or
jumping out of the
way
Excellent! You
should be very
safe
That was amazingly
fast!-Butcould
you do it a second
time?
.125
This is not reactionit's
thought reading!
B51 Nerves or glands?
REQUIREMENTS
Students will need:
activity sheet
diagram sheet
textbook
Notes on the activity
This is a straightforward activity which you can
discuss with the class and then set as homework.
For the class demonstration, you could use cut-out
cardboard glands with Velcro fixed at the back, and a
large outline of the body, with Velcro in the correct
places for attaching the glands.

70 B8 The nervous system and hormones
The nervous system
brain
Position of endocrine glands in the body
cells in the
ear which
detect sound
vibrations
light
sensitive
cells
spinal cord
motor nerve
muscle with receptors
which detect changes
in tension
spinal nerves
sensory nerve
sensors
in the
skin
pituitary gland (beneath
hypothalamus of brain)
thyroid
gland
pancreas
adrenal glands
(capping both
kidneys)
testes (paired)
ovaries (paired)
B52 Hormones to control blood glucose (H)
REQUIREMENTS
Students will need:
activity sheet
diagram sheet
Notes on the activity
A video, computer program or talk from a diabetic student can help to introduce this
activity. Students may also find it helpful to have access to explanatory leaflets and
booklets written to help diabetics.
The task is demanding, requiring sophisticated information processing and
communication skills.
All students will want to cut up and colour in the diagrams to illustrate their account.
Some may find it helpful if they can cut up the information grid and rearrange the
statements before writing their explanation.
Answers to questions
a After a meal, enzymes in the gut break down starch to glucose. Small glucose
molecules pass from the gut into the blood. The level of the glucose in the blood rises.
Cells in the pancreas respond to the rising glucose concentration by producing
insulin and releasing it into the blood. Insulin is a hormone which lets glucose into all
the cells in the body. Increasing the amount of insulin speeds up the removal of glucose
from the blood by muscle, liver, brain and other cells.
During exercise the muscles use energy and the level of glucose in the blood falls.
Glucose concentrations also fall some hours after a meal when little or no sugar enters
the blood from the gut.
When the glucose level in the blood falls, the pancreas cells make less insulin.
This limits the uptake of glucose by cells in the body. The liver stops storing glucose
as glycogen. If the glucose concentration falls too far, other cells in the pancreas

produce another hormone, glucagon, which encourages liver cells to turn glycogen back
into glucose and release it into the blood.
'Feedback' is a term used to describe systems. A signal about the state of the
system 'feeds back' to the control devices. With negative feedback a change in the state
of the system leads to a response which limits the change and tends to bring the output
back to where it was before.
b Many diabetics depend on insulin injections because the cells in their pancreas no
longer make insulin. Without insulin none of the body cells can take in glucose so the
glucose concentration in the blood rises. In time it rises so high that it spills over from
the blood into the urine. Diabetics produce more urine when the glucose concentration
is high so they feel thirsty and drink a lot.
Without insulin the cells cannot get the glucose they need for normal respiration,
even though there is plenty of sugar in the blood. The cells start to break down fats to
get energy for other living processes. This produces fatty acids and ketones. Ketones,
such as acetone, enter the blood. They evaporate easily so they escape from the blood
into the lungs. The air breathed out by an untreated diabetic has a fruity, ketone smell
(like peardrops or nail-varnish remover).
Untreated diabetics steadily lose weight when their body cells cannot use glucose
from the blood and start to break down fats instead.
c Insulin is a protein. Diabetics cannot take the hormone by mouth because their
digestive enzymes would destroy it. Instead diabetics regularly inject insulin. Diabetics
control their blood glucose level by balancing the carbohydrate in the food they eat
against the insulin they inject. A diabetic will have an injection about 30 minutes
before a meal so that insulin gets into the blood in time to allow cells to take in the
glucose from digested food. Ideally the insulin concentration rises and falls in line with
the blood sugar concentration.
Diabetics often have a carbohydrate snack between main meals to stop the insulin
still in the blood lowering the glucose concentration too much. They may need extra
snacks if they take more exercise than usual and their muscles 'burn up' more glucose.
Control is easier if the food contains carbohydrates which the body has to digest
before absorption into the blood. Sugary foods such as sweets, jams and fruit juices are
not so good because the soluble sugars are quickly absorbed and there is a sudden rush of
sugar into the blood.
Other resources
NCS Biology Chapter B12.
Pathways Sourcebook Plants and animals, pages 18-19.
Leaflets and booklets from the British Diabetic Association.
On disc
The disc has a girl's description of her life as an insulin-dependent diabetic. This comes
from the Pathways Sourcebook Plants and animals, pages 18-19.
B8 The nervous system and hormones 71
B53 Hormones and cycles (H)
REQUIREMENTS
activity sheet
scissors
glue (solvent free)
Notes on the activity
This is an important activity, but not an easy one as it includes the concept of negative
feedback. For pupils working at the higher level, it is worth referring to Activity B52.
Both systems are controlled by negative feedback, which restores the concentration to a
mean level. But during a month, the concentration of female sex hormones varies

72 B8 The nervous system and hormones
greatly, compared with glucose which only varies slightly about the mean, on a much
shorter time scale.
Answers to questions
1 The menstrual cycle begins as 2 The increasing amount of FSH in 3 As the ovum grows, the ovary
the pituitary gland starts releasing the blood stimulates the growth of begins to release oestrogen into
FSH into the bloodstream. an ovum in one of the ovaries. the bloodstream.
4 The rising level of oestrogen in
the blood causes two things to
happen:
• less FSH is released-so
no more ova will develop,
• the lining of the uterus
thickens to be ready to
receive the fertilized ovum.
Key:
FSH *
LH
a
oestrogen
•
progesterone •
where the
hormone
comes from
•
where the
hormone £J
acts
8 If the ripe ovum in the oviduct is
not fertilized within a few days,
the 'yellow body' stops making
progesterone and breaks up.
As the level of progesterone falls,
the thickened lining of the uterus
breaks up and menstruation
(bleeding or a 'period') occurs.
7 The 'yellow body' releases
progesterone into the
bloodstream. Progesterone
prevents the pituitary gland
releasing either LH or FSH.
6 The sudden flow of LH in the
blood causes the release of the
ripe ovum from the ovary into the
nearby oviduct. This is ovulation.
In the ovary, the small sac which
held the ovum begins to develop
into a 'yellow body' (corpus
luteum).
5 The ovum continues to ripen,
and the increasing amount of
oestrogen eventually triggers the
release of LH by the pituitary
gland.
b Contraceptive pills contain chemicals which have the same effect on the body as
oestrogen and progesterone. Oestrogen stops the pituitary gland producing the hormone
FSH. This means that eggs stop developing in the ovaries.
Progesterone alters the way the wall of the uterus develops each month making it
less likely that any fertilized egg will implant and start to develop.
Progesterone also thickens the mucus produced by the cells lining the cervix. This
makes it harder for sperm to get through. Progesterone may also help to stop ovulation.
The pill effectively mimics pregnancy. During pregnancy the ovaries and the
placenta produce oestrogen and progesterone which stop the ovaries producing any more
eggs. So a woman taking the pill regularly is infertile.
c Infertility is fairly common. Between 10 and 15 per cent of couples are infertile. It
is equally likely to be the man or the woman who is infertile.
Treatment of the woman with hormones can be effective if she is infertile because
there is something wrong with the glands that influence the menstrual cycle. This is
one of the more successful treatments. The woman takes a 'fertility pill' which contains
a chemical that stimulates her ovaries like a hormone.
Unfortunately, parents are not always counselled about the high risk of twins or a
higher multiple birth (triplets or more). The number of such births has trebled in the

last few years. Half these extra births are the result of IVF. The other half are caused by
'fertility pills'.
Other resources
NCS Biology Chapter B20.
B8 The nervous system and hormones 73
B54 Tropisms in shoots
REQUIREMENTS
Students will need:
activity sheet
sharp scissors
black film can
Access to:
seedlings of cress, mustard or rapid-cycling brassicas
marker pen
filter paper
Blu-tack
Notes:
This is a tropisms activity which works quickly and produces interesting, results which can
be explained quite simply. It only takes a lesson to complete provided seedlings are used
which grow rapidly.
It is a reliable experiment which should provoke some useful discussion. Some of this
discussion may suggest further questions to investigate by experiment. You should allow
some time at the end of the lesson for class discussion of the results obtained. You should
also encourage students to try the follow-up activities suggested below.
If students discuss what happens with others who have done the investigation they will
find that results vary. The hypocotyl always bends upward, but the result depends on where
you cut the seedling off. If tissue at the end of the cut hypocotyl is root material it bends
down. (This is more likely to be the effect of gravity on the less turgid root tissue than a
growth response.) If it is shoot material it bends up. Shoots are negatively geotropic - they
grow in the opposite direction to the force of gravity. Roots are positively geotropic - they
grow in the same direction as the force of gravity. Try examining the hypocotyls or repeat
the investigation with two new seedlings, cutting root material on one and shoot material
on the other.
Other resources
NCS Biology Chapter Bl 1.
B55 Tropisms and plant hormones (H)
REQUIREMENTS
Students will need:
activity sheets, sides 1 and 2
Access to:
reference material, such as biology textbooks
Notes on the activity
This interpretation exercise is pitched at a high level. Students might start by discussing the
descriptions of the investigations in class and then complete the activity for homework.
Discussing the design of the experiments to see how they test a hypothesis (or model) will
help students when they are designing their own Sc 1 investigations.

74 B8 The nervous system and hormones
Some students will find it helpful to be able to refer to other sources of information
such as biology textbooks to supplement the activity sheets and commentary.
Answers to questions
Investigation 1
1 Which part of the tip of a growing plant responds to light?
2 Covering the tip with foil does not stop the shoot growing but prevents it growing
towards the light. The shoot with an uncovered tip bends towards the light. It looks as if it
is growth in the region a little below the tip which makes the shoot bend.
3 There must be some sort of connection between the tip and the part of the shoot which
grows. This could be a chemical connection - a hormone. It could be an electrical
connection involving cell membranes - rather like nerve cells in animals.
Investigation 2
1 Does the tip of a shoot
control growth?
2 The shoot does not grow if
you cut off its tip. Put the tip
back and it starts to grow again.
Something from the tip makes
cells grow.
3 Cells divide to make more
cells in the tip itself. The cells
which grow bigger are in the
region below the tip.
the cells in this region are dividing
the cells in this region are expanding
this diagram shows where cell division and
expansion take place in a growing shoot
Investigation 3
1 Can we separate the hormone which affects plant growth from plant cells?
2 A gel (gelatin or agar jelly) consists of water trapped in a loose network of big
molecules. Soluble chemicals can diffuse in and out of the water trapped in a gel.
3 This investigation shows that the plant hormone can diffuse into an agar gel.
Growth stops when the tip of the shoot is removed. The tip goes on making the
hormone which spreads into the agar. Putting the agar gel on to the cut end of the shoot
lets growth start again. Hormone diffuses from the gel into the region below the tip
where cells grow.
This shows that there does not have to be a direct connection between the tip and the
growing cells. It is therefore unlikely that the signal is electrical, but much more likely
that it is chemical.
Investigation 4
1 Is diffusion of a chemical hormone responsible for phototropism?
2 Cutting off the tip and putting it back on the shoot with gelatin in the cut does not
prevent phototropism. Putting a piece of metal foil in the cut does stop phototropism.
Hormones cannot diffuse through metals.
Investigation 5
1 Does a shoot respond to light because there is more of the growth hormone on one
side than on the other?
2 Hormone from the cut tip diffuses into the agar jelly. Putting a piece of this jelly on
one side of a cut shoot makes the shoot grow and bend even in the dark. This is not an

effect of agar jelly on its own. A fresh, untreated piece of the gel does not make the shoot
grow or bend.
The shoot seems to bend because it grows more in the region underneath the jelly with
the hormone.
3 Phototropism
The results of these
investigations suggest that the
shoot tip is sensitive to light.
Normally the tip produces a
hormone which spreads down to
the cells below. The cells grow
evenly all round the shoot. The
shoot grows straight.
When lit from one side,
growth is faster on the side away
from the light. For some reason
the hormone from the tip
concentrates on the dark side. The
part of the shoot on the side away
from the light grows more so the
shoot bends towards the light.
Other resources
NCS Biology Chapter B11.
. shoot
Lit from the side the shoot grows towards the
light. The hormone concentrates on the side
away from the light.
B8 The nervous system and hormones 75
Lit from above the shoot
grows straight. The
hormone spreads out
evenly from the tip.
shoot
B56 Rights and wrongs of using hormones
REQUIREMENTS
Students will need:
activity sheet
library books
Notes on activity
This activity provides a structure for discussion which encourages everyone in a group to
take part even if they are normally reluctant contributors. Stress from the start that there are
no right answers.
Step a is tackled by individuals and might be a task for homework.
A group size of three to six is fine for step b. Groups aim to reach a consensus.
The grid can be copied onto a transparency for an overhead projector. In step c each
group can record its responses with a tick for statements they all agree with, a cross for
statements they all disagree with, and a blank where they could not reach agreement.
Final discussion can concentrate on the statements which provoked differences of view.
ScO
2 b use scientific knowledge and understanding to evaluate the effects of some applications
of science on health and on the quality of life
Other resources
Pathways Sourcebook Plants and Animals page 20-21.
On disc
The disc has an article called 'Is it natural?' from Pathways Sourcebook Plants and
Animals. The article is about the hormone BST, used to increase milk-production in cows.

Nuffield Biology Section B9
Homeostasis
Context
The maintenance of a constant internal environment is important to well being and
efficiency in all organisms. Changes from the norm have important implications as the
signs, symptoms and causes of various diseases. Hypothermia is a well known example of
the effects of the failure of homeostatic mechanisms.
B57 Keeping a steady state
REQUIREMENTS
Each student will need:
activity sheet
record sheet
Access to:
sink, soap, water and disposable towels
Optional:
blue cobalt chloride paper
liquid crystal thermometer
Safety note
For the activity suggested below
Using students as the objects of investigations needs very careful consideration and care.
There should be no compulsion on them to carry out the activity nor should it become
boisterous or competitive.
It is wise to check with the form tutor or PE department that all students in the class
are fit for the suggested ways of exercising.
Any student who is known to be epileptic, asthmatic or suffer from other bronchial
conditions and/or is excused from the normal school PE activities should not take part in
this type of investigation. See also Safeguards in the school laboratory, ASE, 10th edition
1996.
Notes on the activity
A possible investigation here would be for students to measure their skin temperatures
before, during and after exercise. They can do this at various sites on the body (such as the
forehead, wrist, ankle, and neck) with liquid-crystal fever strips. They might also use blue
cobalt chloride paper to see if they can find a relationship between surface temperature and
the extent of perspiration. Skin needs washing after contact with cobalt chloride paper.
Alternatively, use waterproof low-allergy plaster and record the mass (to nearest 0.01 g)
before and after exercise.
There are links with the work on food chains (Activity B38). Potential energy from
food is transferred to the surrounding air, as heat. This occurs at all levels of the food chain.

B9 Homeostasis 77
Answers to questions
Message (nervous
impulse) along
motor nerves to
breathing muscles
This could usefully be compared with the reflex actions in Activity B50. No sensory nerves
are needed in this reflex arc, because the sensory cells are located in the brain.
Slight rise
in core
temperature
Special sense
cells in the
'thermostat'
in the brain
Messages (nervous
impulses) along
motor nerves
to the liver
and muscles
decreased
metabolic
rate
capillaries near
the surface dilate (diameter
increases) - called vasodilation
more blood travels
near the surface
heat is lost by radiation
temperature returns
to normal

78 B9 Homeostasis
4 A graph could be plotted with skin temperature
on the horizontal axis and units of sweat released
while jogging on the vertical axis.
5 When resting the rate of sweating stays
constant until the skin temperature is above 33 °C
then it rises gradually.
6 The rate of sweating rises much more sharply
with skin temperature when jogging. As well as
cooling the skin, sweating has to carry away the
energy from contracting muscles, which heats up
the blood during exercise.
7 Sweating puts water onto the surface of the
skin where it evaporates. Water (like all liquids)
needs energy to evaporate. The energy is needed to
separate the water molecules so that they break free
from the forces loosely holding them to the other
molecules in the liquid.
As it evaporates sweat takes the energy it needs
from the skin, which then cools.
40-i
CO
o 30-|
0>
03
o>
cc
20-
10-
loggmg
resting
30 31 32 33 34 35 36 37
Skin temperature (°C)
8 Low temperatures slow down body processes. People begin to suffer ill effects if their
core body temperature falls below 35 °C. This is called hypothermia. As the core body
temperature falls towards 28 °C it becomes increasingly likely that the person will die.
Most animals die if their body temperature reaches 45 °C. High temperatures damage
enzymes which control all the chemical changes in living things.
9 In the first 25 minutes of the experiment sweating keeps down the man's skin
temperature despite the high temperature in the hot room.
10 Drinking a lot of cold water chills the man's inner (core) body temperature. The
man's body reacts by cutting the rate of sweating. As a result there is little to cool the
skin so the skin temperature rises sharply in the hot room.
Blood circulating under the skin starts to heat up and, as it circulates, warms the core
of the man's body. As the core inner temperature rises again the rate of sweating
increases and so the skin temperature beings to fall. Eventually the man's body returns to
a steady state.
Opportunities for co-ordination
There are links with changes of state in Physics.
P25 students use electronic sensors.
P62 (Radiation) and P64 (Keeping heat in) are also relevant to thermoregulation.
Other resources
NCS Biology Chapter B12.
B58 What does dialysis do to blood?
REQUIREMENTS
Each student will need:
activity sheet
Visking tubing, 15 cm
rubber band
beaker, 100ml
glass rod
thermometer
Bunsen burner and heatproof mat
disposable plastic gloves
eye protection
the end cut from an old syringe

B9 Homeostasis 79
Access to:
distilled water
glucose test strip, Clinistix (see note 1) (or Benedict's test)
protein test strip, Albustix (see note 1) (or Biuret test)
silver nitrate test solution, 0.01 mol/1 (see safety note )
dropping pipette
artificial 'blood' (see note 2)
Notes:
1 For details of sources see 'Other resources'. The colour changes depend on the
individual test strips and are usually printed on the container. The strips are expensive. They
could be cut lengthways to reduce the cost.
2 Prepare artificial 'blood' by adding to 100 ml water: 0.5 g albumin, 0.5 g salt, 1.0 g
glucose, a few drops of cochineal.
Safety note
Silver nitrate is corrosive or irritant at a concentration of between 0.2 M and 0.5 M.
Supervise your students closely when using the solution. If it is spilled on the skin, the
area must be washed carefully, using a large quantity of running water. Eye protection is
needed when using silver nitrate, or doing Benedict's or the Biuret tests. Remember, Biuret
requires sodium hydroxide solution. The chloride test only requires a very dilute solution.
Notes on the activity
Many students will need help when it comes to'appreciating the significance of the results.
They see another use of Visking tubing but this time with 'model' blood. Again they have
to infer the movement of particles (molecules) from the results of unfamiliar tests. Glucose
and salt pass through the tubing. The red blood cells (modelled by a red pigment in this
experiment) and proteins remain inside the dialysis tubing. The kidney, unlike Visking
tubing, does not simply depend on diffusion through semi-permeable membranes, but can
'pump' some chemicals up a concentration gradient, particularly ammonia, which is very
toxic.
Answers to questions
1 Glucose and salt can pass through the dialysis tubing.
2 Protein and red blood cells do not get through the dialysis tubing.
3 Small particles (such as the particles of sugar and salt) can get through the very small
holes in the dialysis tubing.
The holes in the dialysis tubing are too small to let through red blood cells and large
particles such as protein molecules.
4 Urea particles are small enough to pass out of the 'blood' into the water outside the
dialysis tubing.

80 B9 Homeostasis
5 Urea with some water and salt has been
filtered from the blood.
6 Urine is mainly water with urea and
salts.
7 The dialysis fluid is the same but with
the addition of glucose.
8 In the kidney, glucose is first filtered
from the blood but is then returned to the
blood at a later stage.
9 The glucose concentration in the blood
and in the dialysis fluid is the same.
Glucose molecules move in both directions
through the membrane all the time but
overall there is no change. The
concentration on both sides stays the same.
This makes sure that the glucose
concentration in the blood returning to the
body remains at the same level and is not
lost in the waste dialysis fluid.
water
molecule.
urea
molecule
blood plasma
O
glucose
molecule
o
o
o
o
D— i
D
D
dialysis
tubing
dialysis fluid
10 Digestion of proteins produces amino acids. Breakdown of amino acids in the liver
produces urea. A simple word equation for this process of deamination is:
amino acid —* carbohydrate + ammonia
V
ammonia + carbon dioxide
urea
Normally the kidneys remove urea from blood. People on dialysis eat a low protein diet to
keep down the amount of waste urea to be removed. A lower intake of salt and water also
reduces the amount of these that need to be excreted.
Other resources
NCS Biology Chapter B12.
Pathways Sourcebook Bodywise page 31 gives information about dialysis.

Nuffield Biology Section B10
Cell division
Context
The role of the nucleus in controlling and co-ordinating the cell is a basic biological
concept. The presence of genes on chromosomes has implications for cell function,
hereditary diseases and family likeness. Mitosis and meiosis play important roles in growth,
development and reproduction.
B59 A model of mitosis (H)
REQUIREMENTS
Each group of students will need:
piece of cloth or rough surface about 1/2 m x 1 m (e.g. dishcloth)
string
12 pieces of coloured wool, 18-20 cm in length (4 pieces of each of 3 different colours)
cotton thread
scissors
Blu-Tack or Plasticine
2 small rings (to pull the threads through)
sticky tape
Notes on the activity
Pupils are introduced to the process of mitosis by making a model. It is not intended to
refer to individual 'stages' in the mitotic process; the whole should be seen rather as a series
of events merging into each other.
The idea of genes as sections of the DNA in a chromosome which are responsible for
particular characteristics can be developed. It is sometimes the case, however, that a
combination of several genes is responsible for a given characteristic.
Answers to questions
1 The chromosomes separate from their partners and move towards the poles of the cell.
2 The chromosomes have been replicated (copied) exactly, and each new nucleus contains
an exact copy of each chromosome because of the way the chromosomes have separated.
Other resources
NCS Biology Chapter B21.

82 B10 Cell division
B60 Cells dividing (H)
REQUIREMENTS
Students will need:
activity sheet
scalpel (see safety note 1)
cutting board
stoppered flat-bottomed tube
watch glass
mounted needle
teat pipette
microscope slide
cover slip
eye protection
Access to:
roots in fresh, growing condition (see note 1)
dilute hydrochloric acid
water bath at 60 °C
distilled water
acetic orcein or other suitable
stain in dropper bottle (see note 2)
paper towels
microscope and lamp
scissors to cut paper
plain paper
paper glue (solvent free)
Optional for the teacher:
projection microscope
toothpick
Notes:
1 Some people have success with garlic or onion roots; others prefer peas or beans.
Crocus corms are better still with fewer, bigger chromosomes. (Philip Harris can supply.)
Bulbs and seeds can often be induced to produce roots in the laboratory all the year round.
Arrange bulbs or corms with their bases sitting on water, by supporting them in a beaker
with matches or toothpicks. Special vases for this purpose are available but not really
necessary. Keep the bulbs in the dark or in subdued light.
Bulbs tend to become dormant during the autumn and winter. This can be overcome by
keeping them in a refrigerator for 4-6 weeks. If they are then treated as shown in the
picture, roots should be produced within a week.
Seeds of Vlciafaba can be germinated all the year round and will produce suitable root
material. The following procedure can also be adopted. Soak the seeds in water for 24-36
hours.
Remove the cracked testas and plant the seeds in damp vermiculite.
After two days when the radicle is about 2 cm long, remove 2-3 mm from its tip. This
will stimulate growth of lateral roots.
After a week in damp but not flooded vermiculite a crop of 15 beans should provide
sufficient roots for a class of 30.
If you use peas you may need to carry out trial germinations to find how long it takes
to produce roots at the right stage for the investigation. This varies with the conditions,
including the temperature and the time of year.
2 Prepare acetic orcein by placing 45 cm3 glacial acetic acid with 55 cm3 distilled water in
a flask fitted with a reflux condenser. Add 1-2 g synthetic orcein and some anti-bumping
granules. Boil gently for 10-15 minutes. Allow to cool and filter. Prepared acetic-orcein
can be obtained from biological supply agencies.

B10 Cell division 83
Safety notes
1 Be vigilant while your students are using scalpels. Check that they dispose of waste
roots correctly.
2 The stain is corrosive, so ensure students keep it away from their skin and eyes.
Notes on the activity
Most students can achieve some success with this activity. It is important that the material
separates out enough to form a single layer of cells without squashing them completely.
Students have three samples to use. Suggest that they go through the squashing and tapping
process with the section taken from furthest from the tip first. When they have examined
this sample they will know better how to deal with the other sections.
You may want to introduce the term mitosis. All the stages of mitosis should be
visible in the samples from a whole class. A projection microscope, if available, is
particularly useful with this activity, as you can point out the structures which students are
looking for. A video sequence will also emphasize the smooth transition from one stage of
mitosis to the next. Following the practical activity, students could make the flick book
(Activity B61).
An observant student with a carefullyadjusted
microscope should be able to see
this amount of detail. These are cells close
to the tip of the root of a lily.
The diagram below arranges the stages into a cycle (called the cell cycle).
membrane round
the nucleus
chromosome
cell membrane
Chromosomes are visible in the
nucleus just before the cells
divide.
two 'daughter'
cells each with
a nucleus
The chromosomes shorten and
thicken. They can now be seen
to consist of two paired strands.
cell starting to
split in two
The chromosome pairs gather The chromosomes pairs split and
near the middle of the cell. move to opposite i !>:>'J" Lana
After cell division the chromosomes are no longer clearly visible.
During this in-between stage each chromosome duplicates
itself again ready for another division.
The cell divides. Each new cell
forms a nucleus with a complete
set of chromosomes.
Answers to questions
1 The chromosomes are in the nucleus of the cell.
2 Mitosis is the name for this type of nuclear division. At the beginning of mitosis, a
copy is made of each chromosome. Under the microscope we see a chromosome with its
copy, joined together. The pairs of chromosomes then line up in the middle of the cell and
are pulled apart to opposite ends of the cell. Then the cytoplasm divides, leaving one copy
of each chromosome at each end. Thus each of the new cells has a full set of chromosomes.
In mitosis the chromosomes copy themselves before the cell divides in two. Each new
cell gets one full set of chromosomes.

84 B10 Cell division
B61A flick book to show mitosis (H)
REQUIREMENTS
scissors
glue
stapler
Notes on the activity
Before using this worksheet, students should examine slides, photographs or diagrams of
cells undergoing mitotic division of the nucleus. It is probably inappropriate for students to
memorize the terms used to describe the stages of mitosis. It could be argued that this tends
to make students think of the process as a series of jerky steps rather than a smooth and
continuous process. The use of a flicker book attempts to overcome this problem. The
important points to bring out of this activity are as follows:
• the genetic information is stored in thread-like chromosomes,
• the chromosomes are copied immediately before division so that, when they are visible
for the first time, each chromosome appears as one double thread. Each copy is called a
chromatid,
• the genetic information in each chromatid is the same,
• the chromatids separate so that each daughter cell receives the same genetic information
as the parent. As soon as the chromatids separate they are called chromosomes.
For brighter students, the diagrams could be given in a random sequence so that they
have to be arranged correctly before they are stapled together.
Students should be able to identify key structures such as: nucleus, nuclear membrane,
chromosome, chromatid, pole, spindle, equator.
They could also be asked to write a narrative explaining the sequence of pictures.
Other resources
There is computer software for making flick books, e.g. MAC Flipbook.
B62 DNA, genes and protein synthesis (H)
REQUIREMENTS
Each group of students will need:
activity sheet (including disposable copy of side 3)
scissors
sticky tape
Notes on the activity
The ideas of genes as particular sequences of bases in DNA and the synthesis of proteins
are introduced by a series of 'cut out' models. The essence of this activity is not for the
pupils to remember the details but to appreciate that:
• The genetic code represented by the sequence of bases along the DNA can be translated
into a message which is read during protein synthesis, and
• Particular amino acids are coded by groups of three bases (triplets).
As an extension exercise, students could be asked to suggest how DNA replicates itself in
terms of the nucleotide pairing.
Background information
All the stages mentioned in the worksheet are catalysed by enzymes. For example, an
enzyme catalyses the unwinding of DNA, another enzyme catalyses the condensation
reactions which make the mRNA, and other enzymes are responsible for binding the tRNA
to the ribosomes. RNA stands for ribonucleic acid; it differs from DNA in having the base
uracil in place of thymine, and having a different sugar from that in DNA. The code itself
is non-overlapping; sections of the same gene are not used for more than one type of

B10 Cell division 85
protein. The bases on the mRNA are complementary to those on the DNA. Proteins are
synthesized on the ribosomes, where the mRNA and tRNA carrying the amino acids come
close to each other and form specific bonds between the triplets on the mRNA and the
anticodon bases on the tRNA. The codons on the mRNA are specific for particular amino
acids, but many amino acids have more than one code; for example, the amino acid glycine
can be coded for by GGG, GGA etc. The example on the worksheet gives GGG as the
messenger code for glycine, and this corresponds to the DNA code CCC. The amino acids
are attached to the tRNA earlier in the processes. As the ribosomes and mRNA move over
each other, the tRNAs are brought to the mRNA one by one and the protein chain is
gradually built up, as shown diagrammatically below.
. protein chain growing
amino acids
incoming tRNA
mRNA
Answers to questions
ribosome
1 Condensation is a reaction in which pairs of molecules join together with the
elimination of a small molecule (in this case, water). Other examples include building up
starch from glucose. Digestion (hydrolysis) is the reverse of condensation.
2 The weak bonds between the bases are those which are the most likely to break.
3 This is a mutation, which would prevent the correct protein being made by the gene. In
an adult it may only affect a few cells. A mutation in a developing embryo may affect a
large part of the body. Mutations can be passed on in the gametes. They are then called
inherited diseases.
Opportunities for co-ordination
C17 explains how polymers are made
Other resources
Pathways Sourcebook New life pages 22-3 and 25 give information about DNA.
B63 Chromosomes in sex cells (H)
REQUIREMENTS
Students will need:
activity sheet
diagram sheet

86 B10 Cell division
Notes on the activity
At this level the important idea is that the chromosomes copy themselves once but the
nucleus divides twice, thus halving the number of chromosomes in the nucleus of each sex
cell.
Answers to the question
5 The cells in the ball
keep dividing as it
moves down the oviduct.
It is now called an embryo
4 After several hours, a
ballot cells is formed
3 The fertilized
cell divides
6 Implantation. The
embryo sinks into
the soft lining of the
uterus
\
placenta
forming
b Match the diagrams and captions as follows:
A - Chrosomes ...
B - Each chromosome ...
C - The nuclear membrane ...
D - The chromosome pairs ...
E - The two copies ...
F - Four nuclei ...
1
Nuclear division to make the nucleus of body cells
(mitosis)
The chromosomes double - the nucleus divides once
Two nuclei are made
Nuclei are identical
Each new nucleus gets a full set of chromosomes
Takes place during growth and maintenance of the
body and in asexual reproduction
2 Fertilization.
A sperm nucleus
fuses with the
egg nucleus
1 Ovulation. The ovary
releases an egg into the
oviduct
Nuclear division to make the nucleus of sex cells
(meiosis)
The chromosomes double but the nucleus divides
twice
Four nuclei are made
Nuclei are all different
Each nucleus gets a half set of chromosomes
Takes place in ovaries, testes and pollen sacs
cell in the testis
dividing to form
sperm
dividing to form
*'
eggs
"If® fertilization
i
T
(46) fertilized cell (zygote)
i
n.isn ball of dividing
sfon cells (embryo)

B10 Cell division 87
3 When gametes are being formed, the number of chromosomes in their nuclei is halved.
So when an egg and sperm nucleus join at fertilization, the original number (46) is
restored.
parent's body cells
46 chromosomes
sperm
23 chromosomes^
. fertilized egg
• 46 chromosomes
child's body cells
46 chromosomes
23 chromosomes
Other resources
NCS Biology Chapter B19.

Nuffield Biology Section B11
Variation
Context
This section explores the causes and types of variation in organisms. The relative
importance of genetic and environmental contributions to variation are considered.
B64 Variation in people
REQUIREMENTS
Students will need:
activity sheet sides 1 and 2
Access to:
rulers
tape measures
bathroom scales
Desirable but not essential:
computer and suitable database program
data from previous classes for comparisons
Note:
Various database programs are suitable for processing data. Students can interrogate most
school databases to get the information mentioned on side 2, but students should not be
identified by name.
Notes on the activity
There is a danger that activities such as this can provoke overt racial prejudice. You will
need to be sensitive towards the feelings of students who vary markedly from the norm.
Such differences may be brought out in this activity. There are many reasons for variations
in size and early or late growth and development. Avoid the term 'normal' to mean average
or close on the norm, as this implies that extreme values are 'abnormal'. Instead, you could
talk about 'the normal range' since this includes the extremes.
If you are going to use side 2 you should ensure that some students measure the
heights and masses of students in the class. Computers make the storage and retrieval of
data for comparisons within and between year groups simple and effective. You can also
build up a growing data file year by year.
Point out that the value of a pie chart is that it displays the distribution of heights or
masses in the whole sample studied.
Some students will need help with the terms range, commonest value and average
value. It may be worth checking with the Maths department to find out how they define
these terms. Discourage students from using the term most popular instead of commonest
and comment on the difference in meaning.
Some questions which might be investigated:
• Do tall people have a wide arm span?
• Do people with a wide arm span also have long legs?
• Do people with long legs walk faster?
• Are boys or girls more likely to be left-handed? (Note that this one is discontinuous.)

B11 Variation 89
Continuous variation, controlled by Discontinuous variation, controlled
many pairs of genes and by the
by a single pair of genes or a small
environment.
number of pairs.
height
handedness
mass
nose shape
reach
fingerprints
arm span
shape of thumb
leg length
shape of ear lobes
length of stride
tongue rolling
freckles
blood group
(Some examples, such as eye colour and
tongue rolling, are not as simple as was
once thought and should not be used as
examples to explain Mendelian
inheritance.)
When we plot the results of measuring continuous variation we often get a 'bellshaped'
curve. Most individuals are close to the centre of the range - the norm. The
number of individuals differing from the norm falls away as the difference from the norm
gets bigger. We call this pattern of variation a normal distribution.
Children inherit some features from their parents. The drawing shows some examples
of inherited features. Other inherited features are: sex, thumb shape, handedness, and the
general form of fingerprints.
hair colour
hair type
(straight or wavy)
freckles
shape of ear lobe
skin colour
Children pick up some features from the conditions in which they live or grow (their
environment). These features include such things as the language they speak, their ability to
swim, and the amount and types of food they like to eat.
Many features are affected by both inheritance and environment (which includes diet) -
height, for example.
Note: The quotation at the beginning of the activity sheet is from The Task by
William Cowper (1781-1800).
ScO
Id judge when to use IT to collect, handle and investigate scientific information
Other resources
NCS Biology Chapter B22.
Nuffleld Science Calculations, Topic 41 (Continuous and discontiuous variation).

90 B11 Variation
B65 Variation in ivy leaves
REQUIREMENTS
Students will need:
activity sheet
ruler
Access to:
ivy leaves or ivy growing up a tree or wall (see note 1)
measuring instrument (depending on students' plans) (see note 2)
Notes:
1 It may be convenient to pick some ivy leaves, put them into labelled plastic bags, and
then use them with several classes. Another possibility is to do this activity as part of a
field course or field study week. If so, students can measure the leaves on the spot. You
may even be lucky enough to have some suitable ivy growing in the grounds of the school.
2 Suitable measuring instruments might include: tape measures, metre rules,
thermometers (or temperature sensors with portable data loggers), light meters or light
sensors with portable data loggers), narrow range pH paper.
Safety notes
1 Students should wash their hands after handling ivy leaves.
2 If possible use spirit-in-glass rather than mercury-in-glass thermometers.
Notes on the activity
This activity concerns variation brought about by environmental differences. Students
planning a Sc 1 investigation will want to measure variables which might affect the ivy
leaves. This activity is also an important opportunity to revise work on plant growth.
Factors which might affect the growth of leaves include: brightness of sunlight,
moisture, temperature, degree of shelter from the wind, moisture content of the soil,
nutrients in the soil, distance along the stem from roots to the leaf, height above the
ground. There is also a difference between ivy leaves growing on a stem which is attached,
and leaves growing on an unsurported stem, e.g. above a fence.
Students might set out to answer questions such as these:
• Do ivy leaves grow bigger in sunny or shady places,
• Do leaves near the ground grow bigger than leaves up a tree?
They might collect samples of about 50 leaves from different parts of the same plant. It
then seems likely that any differences in their growth are due to changes in the environment
and not to heredity.
You could refer here to Activity B28. If cuttings, all taken from the same plant, are
used to study mineral deficiency, the investigation will be a fair test since there is no
genetic variation. If different plants are used, such as duckweed, a large group of plants is
needed in each solution, with the assumption that each group will have a similar range of
genetic types.
Here are some sample results from a student who measured the widths of 35 leaves
from an ivy plant.
Leaf widths in mm
23 34 35 47 89 87 66
84 26 57 75 32 96 75
46 35 22 21 8 19 17
65 56 43 38 67 21 42
18 77 23 43 55 65 35
The lowest value is 8 and the highest value is 96. To display these results as a frequency
diagram, put them into groups which increase in equal steps.

B11 Variation 91
Group
Width range
/ mm
Number of
leaves
1
0-19
4
2
20-39
12
3
40-59
8
4
60-79
7
5
80-99
4
Other resources
Nuffield Science Calculations, Topic 41 (Continuous and discontiuous variation).
B66 Generations of tomato plants (H)
REQUIREMENTS
Students will need:
activity sheet parts 1 and 2
Access to:
parent, FI and F2 tomato plants grown in pots (see note)
colouring pens or crayons
Note:
Tomato seeds for genetic demonstrations are available from Philip Harris. The lesson kits
contain seeds of the parental type, as well as of the FI and F2 progeny. For this activity use
the cotyledon colour set (H13270/0). This set illustrates monohybrid inheritance with
incomplete dominance. (F! means first filial generation.)
Notes on the activity
We have deliberately suggested an example to illustrate the independent assortment of genes
before introducing the theory of dominance.
The activity sheet asks students to make predictions before they have a theoretical basis
for doing so. This is worth doing because it will encourage many of them to take a closer
look at the seedlings. They are quite likely to predict that the FI generation will be yellowgreen.
This helps to emphasize the surprise that the F2 seedlings are not yellow-green but a
mixture of green and yellow.
Invite students to consider a model in which each parent plant contributes a single
instruction (gene) about seedling colour. The Fj seedling thus receives two different
instructions and ends up with a seedling colour which is in between. What then happens in
the next generation? Does each F! seedling hand on a single instruction which says be
yellow-green? The results show that this is wrong, hence the need for a more complex
model, illustrated by side 2 of the activity sheet.
You may want to raise the question 'How can we tell that these effects are not due to
mineral deficiencies?' The answer is that all the plants were grown in the same compost to
make this a fair test. This is an opportunity to refer to the study of plant nutrition.
Which type of pollen joins with which ovule (egg) is pure chance. The complete
diagram shows that if we grow lots of seeds we can expect to get two yellow-green
seedlings for every green seedling and every yellow seedling.

92 B11 Variation
First cross
alleles in parent
body cells
G allele: seed leaves green
Y allele: seed leaves yellow
alleles in sex cells
alleles in cells of firstgeneration
plants (F^
Second cross
F, plants used
as parents
alleles in sex cells
alleles in cells of green leaves yellow-green leaves^ yellow leaves
second-generation ~
plants
GY
Students working at the higher level should be able to construct their own genetics
diagrams. An alternative form, which they may find easier, uses a grid called a Punnett
Square (named after R. C. Punnett, an early geneticist):
Second cross
F, plants used
as parents
alleles in
sex cells
alleles in cells
of secondgeneration
plants
yellow-green
leaves
GY
M3J or (Y)
©
©
x
GD
GG
green
GY
yellow-green
yellow-green
leaves
GY
CD or CL
(V)
GY
yellow-green
YY
yellow
The probabilities of finding each genotype in the F2 generation are therefore in the ratio 1:2:1.
In this example, where neither allele is dominant, the ratio of phenotypes is also 1:2:1.
Other resources
Nuffield Science Calculations, Topic 42 (Inheritance of characteristics) and Topic 38
(Testing predictions). This explains the Chi-squared test for more advanced students.
B67 Making an identification key
REQUIREMENTS
activity sheet
paper
scissors
felt tip pens
other key sheets

Notes on the activity
This is really revision of Key stage 3 material. Teacher input may be required for the
simple mechanics of using a key and you might like to have other keys available.
The lichen key was chosen as you might like to fit identification keys into work on
pollution and it makes a change from the usual keys available. It is always best to show
pupils the real thing if possible, but take them to the lichens rather than the other way
around!
B11 Variation 93
How to use the key:
• Start at the pair of descriptions numbered 1. Decide which description fits the lichen
you are trying to identify.
• THEN move to the new pair of descriptions whose number is shown next to the
description that fits your lichen.
• Carry on like this until you get to a line which has the lichen name at the end of it.
To test understanding of a key you may like to use these questions in your
discussion with students.
Answers to questions
• What lichen names do you get if you follow these paths through the key?
start at 1 end at 4
start at 1 end at 2
start at 1 end at 3
• Which lichens could not be identified if you started at 2 ?
Asking pupils to modify the key also tests understanding and the efficiency with
which they do it gives a good indication of understanding.
The construction of a table of information using a key can be used as extension
material. For example a published arthropod key could be translated into a table like this:
Characteristics
Exoskeleton
present
Body divided into
head, thorax and
abdomen
Has wings
Has jointed limbs
Has antennae
Animal
A
yes
yes
no
six
one pair
Animal
B
yes
no
no
many
more than
six
two pairs
Animal
C
yes
yes
two pairs
six
one pair
Animal
D
yes
no
no
eight
no
Animal
E
yes
no
no
many
more than
six
one pair
Animal
F
yes
yes
one pair
six
one pair
The last activity can throw up lots of useful discussion points about key construction.
A dichotomous key has repeated pairs of questions, so that there is a series of pairs of
branches. Each branch ends in the name of one of the organisms, or else in another
question. If students have specimens to move about and group together, then key
construction is easier to understand. You could use the lichens as an example. If you don't
have actual specimens, you could cut out the five diagrams separately from the activity
sheet. You could use the keys with other groups and they could make attractive wall
displays.

94 B11 Variation
1 Where do
they grow?
Flat
Parmelia
subrudecta
On the bark
2 Are they flat
or branched?
Branched
3 How long are
the branches?
Bright
orange
Xanthoria
On rocks
4 What colour
a re they?
\
Pale
grey-green
Parmelia
saxatilis
Long and
dangling
Usnea
Short
Evernia
The questions are then numbered and the key can be rewritten as it is on the activity sheet.
Notice that the number of pairs of questions is always one less than the number of
organisms.
ScO
4 a use a wide range of scientific and technical vocabulary and conventions, and to use
diagrams, graphs, tables and charts to communicate information and to develop an
argument

Nuffield Biology Section B12
Inheritance (Mendelian genetics)
Context
This section deals with Mendelian genetics. The way in which gender is inherited in
humans is used to introduce the concept that both parents contribute equal amounts of
genetic information to their offspring. Monohybrid inheritance involving simple
dominance is developed using 'family tree' pedigree analysis. The concept is considered
that some diseases may be inherited and that it is possible to predict the chance that this
may happen. Genes are defined as functional units of DNA. The basic principles of
cloning and its significance in producing crop plants is considered. Selective breeding as a
means of creating desired combinations of characteristics is explored. The principles of
genetic engineering are outlined and an opportunity is provided to discuss some of the
issues arising from this technology.
B68 Breeding with beads (H)
REQUIREMENTS
Each group of students will need:
beads, plastic 'poppet', in 2 contrasting colours; 200 of each colour
3 beakers for the beads
marker pen or chalk
Notes on the activity
The procedure is detailed on the worksheet.
This simulation exercise works well, provided that the students fully appreciate what
the beads and the beakers symbolize. It is important that the concepts of genes and alleles
are explained carefully, since this is a fertile area for confusion.
Provided that the number of zygotes 'made' is small compared with the number of
beads in the containers it does not matter whether the beads are retained or returned after
being taken out.
B69 Skipping a generation (H)
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
The study of family trees in which inherited characteristics skip a generation leads to the
idea that one inherited instruction 'overpowers' the other hence the notion of dominant and
recessive characteristics.
A simple model of a simple pattern of inheritance uses small pieces of coloured card
to represent two alleles of a gene controlling a characteristic. Take two pieces of A4 card,
one white and one coloured. Cut each piece of card into 180 small squares. Put all the
squares of card into a box and mix well. Now pass the box round the class and ask each
student to take out two squares, without looking. Tell them that the coloured squares
represent the dominant allele of a gene controlling, say, ear lobe shape. Now students can
count the number of offspring which will show the feature controlled by the dominant
allele.

96 B12 Inheritance
This is a good moment to point out to students that the examples used in the
activities are deliberately oversimplified to help students to master the basic ideas of
genetics. In general (and including eye colour) characteristics are affected by more than one
gene and patterns of inheritance are complex. This can help to deal with questions such as
'If this is right, how come I've got black hair and both of my parents have fair hair?' Such
exchanges may be the beginnings of a discovery that the student was adopted or abandoned,
which can be painful and needs very careful handling.
In Steve Jones' book The Language of Genes, he makes the point that all visible
characteristics are determined by both nature and nuture. It is actually an important thing
to stress - that some genetic conditions prevail regardless of environment whereas others
(like the Himalayan mutation of Siamese cats - leading to black extremities due to cold)
need special conditions to reveal them. He makes the observation that, if we were all
tobacco smokers, lung cancer would be a genetic disease. People with genes predisposing
them to lung cancer do not usually develop it without the environmental trigger.
Answers to questions
1 None of the grandparents' children has red hair.
2 Four of the grandchildren are boys.
3 Two grandchildren have red hair: one boy and one girl.
4 The grandchildren have three uncles.
5 In these diagrams we use these symbols:
• B for the dominant allele for brown hair,
• b for the recessive allele for red hair.
The grandparents carry a pair of identical alleles: BB if they have brown hair and bb if
they have red hair. They are therefore homozygous for hair colour.
The first generation of children, including Tom Davies and Mary Jones, all inherit one
dominant allele (B) and one recessive allele (b). This means that their genotype is
heterozygous, and they show the dominant phenotype (brown hair).
Students should appreciate that a genetic diagram shows probabilities. So if a parent
is homozygous, only one gamete need be drawn, since all the gametes will have the same
gene. Students may prefer to draw two each time, for consistency, but this makes some
diagrams unnecessarily complex.
Fj phenotype
brown hair
brown hair
genotype
Bb
Bb
gametes
(jT) (V)
F2 genotypes
and
phenotypes
©
©
BB
brown
©
Bb
brown
©
Bb
brown
bb
red
F2 genotypes
ratio of probabilities
of genotypes
F2 phenotypes
ratio of probabilities
of phenotypes
BB Bb bb
1:2:
brown hair
1
red hair
3 : t
6 Emma and Simon both have red hair. They must have inherited the recessive allele
from both parents (bb).
7 Tracey, Richard, Paul and Robert have brown hair. They must have inherited at least
one dominant allele, but they may have inherited two (either Bb or BB).

B12 Inheritance 97
ScO
4 c present scientific information in symbolic or mathematical form
Other resources
NCS Biology Chapter B22.
B70 Sex-linked inheritance (H)
REQUIREMENTS
Students will need:
activity sheet
textbook
Notes on the activity
This topic needs careful handling in the classroom (see the notes on Sensitive issues,
pages 5-6). First, there is the question of students who suffer from the disease concerned.
All teachers are likely to come across these diseases at some time in their career. School
medical records may be good but they are not infallible: assume that every class may
include a sufferer, a friend of a sufferer or a relative of a sufferer. Take care not to use
words like mutant. Avoid using 'normal' to describe a person with the dominant
phenotype as this implies that a sufferer is abnormal, i.e. talk about a person with normal
blood clotting not a normal person.
Teachers should also be aware that discussion of inherited diseases can identify
parentage, or students could discover that they were adopted. Teachers should be very
careful about references to what parents are like. If these lessons cause distress in students
or lead to chains of questions outside the point of the lesson, the parents should be
informed as soon as possible.
Answers to questions
1 People with haemophilia cannot make the protein which helps blood to clot. If they
cut themselves they keep on bleeding. If bruised, they go on bleeding inside the body.
Even small cuts and bruises can be dangerous.
2 The main treatment for haemophilia is to inject the missing protein, factor VIII.
Someone with haemophilia may need other injections to treat the effects of the disease, for
example injections of enzymes to remove blood which has bled into joints.
3 Family life can be enjoyable and energetic even if one of the family has haemophilia.
Others in the family have to keep the problem in mind and they help him with the
injections. Injections can take a long time and be painful. This can be distressing for
everyone involved.
4 Haemophilia is a sex-linked disease. The cause of the disease is a gene on the X
chromosome. The form which causes the condition is recessive.
A woman has two X chromosomes, so she can be a symptomless carrier (she can
carry the gene without being affected by it). The dominant gene on the other X
chromosome means that her body makes the protein for blood clotting.
A man with the recessive gene on his single sex chromosome is affected by the
disease because the Y chromosome is short and carries few genes other than those which
determine masculinity. So there is no second copy of the gene for blood clotting.

98 B12 Inheritance
5 Parental father with normal carrier mother with
phenotypes blood clotting normal blood clotting
Parental
genotypes
XHY
XHXh
gametes
F, genotypes
and
phenotypes
©
©
XHXH
girl with
normal bloodclotting
©
XHX"
carrier girl with
normal bloodclotting
0
XHY
boy with
normal bloodclotting
XhY
boy with
haemophilia
6 If the mother is a carrier there is a 1 in 2 chance that:
• a daughter will be a carrier,
• a son will be affected.
7 A sex-linked characteristic is a recessive characteristic controlled by a gene on the X
chromosome. So it is much more common in males, who do not have the chance of a
second, dominant allele to hide its effects.
8 Only a daughter of a haemophiliac man and a carrier mother can inherit two X
chromosomes both with the allele for haemophilia.
Haemophilia affects one male in 25 000. Assuming the frequency of female carriers is
similar, then the chance of both parents having the haemophilia gene is 1/25 OOO2. Their
daughters would have an equal chance of being a carrier or having haemophilia. So the
chance of the daughter having haemophilia is 1/25 OOO2 x 1/2
9
Parental
phenotypes
father with colour
blindness
mother homozygous
for normal colour vision
Parental
genotypes
XbY
x
xBXB
gametes
F, genotypes
and
phenotypes
(x")
©
©
XBXb
carrier girl with
normal colour
vision
XBY
boy with
normal colour
vision
Note that a man cannot pass the recessive gene to his sons because they inherit his Y
chromosome, not the X chromosome.
ScO
4 c present scientific information in symbolic or mathematical form.
Other resources
Pathways Sourcebook New Life pages 16-17
Nuffield Science Calculations, Topic 42 (Innheritance of characteristics).

B71 Two inherited diseases (H)
B12 Inheritance 99
REQUIREMENTS
Students will need:
activity sheet
textbooks
Notes on the activity
See B70 for comments on sensitive handling of the topic.
Answers to questions
1 Inherited disorders are caused by a change in a gene, which therefore does not code for
the correct protein, e.g. the sickle-cell gene has the codon GUA instead of GAA. It
therefore codes for valine instead of glutamic acid. This single amino acid difference makes
the haemoglobin much less efficient at carrying oxygen. It also tends to crystallize and
distort the shape of the red cells.
If an infectious disease (e.g. rubella) affects an unborn baby, then the resulting
damage, e.g. blindness, would be called congenital, not inherited. It could not be passed on
to future generations.
2 Alleles are alternative forms of genes. In many cases, one allele will only have an
effect if no other alleles are present. It is then said to be recessive, e.g. the gene for cystic
fibrosis. A gene which has an effect even in the presence of other alleles is said to be
dominant, e.g. in the ABO blood groups, the allele for group O is recessive to the other
two alleles. In this case the genes for groups A and B are equally dominant (co-dominant).
Sickle-cell anaemia is another unusual case, where the gene for normal haemoglobin is not
completely dominant.
An individual who is heterozygous for an inherited disorder is said to be a carrier.
This is not to be confused with the carrier of an infectious disease (e.g. typhoid fever) who
harbours the germ, and can pass it on, without showing symptoms themselves.
3 Cystic fibrosis affects the lungs. Thick mucus coats the cells which line the tubes in
the lungs. This clogs up the lungs and makes breathing difficult. The mucus also blocks
the pancreatic duct and so affects digestion, making it difficult to digest fats.
4 People with cystic fibrosis have to clear the thick mucus from their lungs. A face
mask can help them to cough up mucus. They take pills before a meal to help with
digestion. They also take extra vitamins. It is important to avoid infections, especially
lung infections, so they start taking antibiotics if they catch a bacterial disease.
5 The allele for cystic fibrosis is recessive.
6
Parental
carrier father carrier mother
genotypes
Ff
Ff
gametes (7) (7) (7) (7)
F, genotypes
and
phenotypes
©
0
©
FF
not
affected
Ff
carrier
0
Ff
carrier
ff
cystic
fibrosis
7 A baby can only get cystic fibrosis if he or she inherits two recessive alleles, one
from each parent. This means that both parents must be carriers (Ff)-

100 B12 Inheritance
8 If both parents are carriers, there is a 1 in 4 chance that any baby will be affected by
cystic fibrosis.
9 In sickle-cell anaemia, the haemoglobin is much less efficient at carrying oxygen
causing anaemia. The red blood cells become distorted into a sickle shape, and can then
block the capillaries, causing serious illness.
10 In sickle-cell trait, there is only slight anaemia. The malarial parasite cannot live in
red cells with sickle haemoglobin, so the heterozygous condition has survival value in
areas where malaria is endemic.
11 The chance is 1 in 2. So in areas with malaria, this allele has spread.
Other resources
NCS Biology Chapter B22.
Pathways Sourcebook New life pages 16-17, 20-21 gives information about inherited
diseases.
B72 Genes (H)
REQUIREMENTS
Students will need:
copies of the activity sheet
textbook
Notes on the activity
This activity leads to a basic summary of the key ideas which students meet in this topic.
For some students you may want to cover up the lowest box and the bottom two diagrams
so that they concentrate on the idea that genes are carried by chromosomes in the nucleus
of the cell.
Students working at the higher level could expand on the worksheet to explain an
example such as sickle-cell haemoglobin (see Answers to questions for B71).
The job done by the nucleus of a cell
The nucleus is the control centre of a cell.
The strands seen in the nucleus when cells divide
The strands are chromosomes. Every cell in the body has identical chromosomes with the
same genetic information.
The materials of which genes are made
Molecules of DNA in chromosomes carry the genetic code which controls development
and life processes in living things. The letters DNA stand for deoxyribonucleic acid. A
DNA molecule consists of two long strands spiralling round each other.
The job of a gene
A gene is a section of the DNA molecule. Genes control all the characteristics which
children inherit from their parents. In the simplest examples, one pair of alleles (one from
each parent) controls one characteristic, e.g. nose shape. But many characteristics which
show continuous variations, e.g. human height, depend on many pairs of alleles.
Substances formed in cells under the control of genes
Each gene controls the formation of a protein. All enzymes are proteins, and it is enzymes
which act as catalysts for all the chemical processes in cells. So the sequence is:
gene —> protein (enzyme) —> chemical reaction —> characteristic
Opportunities for co-ordination
C17 explains how polymers are made.
Other resources
Pathways Sourcebook New Life pages 14-19

B73 Genetic engineering (H)
B12 Inheritance 101
REQUIREMENTS
Students will need:
activity sheet
Optional access to:
modelling materials
Notes on the activity
This activity covers the use of genetic engineering and includes some revision questions
about the action of insulin. The activity should be introduced with a brief review of the
work on insulin and then a discussion of the key ideas on the sheet before students attempt
it.
The process of excision and joining of sections of DNA can be modelled by making
wool genes and cutting and inserting genes at the relevant place. Restriction endonuclease
enzymes cleave the DNA, and different types of enzyme cut the DNA at specific base
sequences. Plasmids are small sections of DNA which have an independent existence in the
cytoplasm and are not part of the ordinary DNA of a cell. They are found in many
organisms and the cell can normally survive without them. To date, most genetically
engineered proteins have either used plasmids or viruses to convey the foreign gene, not
the main DNA of the cell. Another fascinating way of introducing genes is to literally
shoot the cells with gold particles coated in DNA. Some of these cells then take on the
new characteristics.
In the manufacture of genetically engineered insulin, only a small proportion of the
bacterial cells is successfully infected with the changed DNA. A gene with antibiotic
resistance is used as a marker to recognize bacteria which have been successfully infected.
Such bacteria containing the insulin gene may be identified by growing the bacteria on a
medium containing the antibiotic: only those with antibiotic resistance survive.
Other proteins which have been genetically engineered include human growth
hormone and vaccines for hepatitis B and foot-and-mouth disease. In 1992 genetically
engineered factor VIE was first used in the UK to treat a haemophiliac patient undergoing
surgery. Genetically engineered blood products avoid the danger of infection by viruses
such as HIV and hepatitis.
Answers to questions
1 Many diabetics need regular injections of insulin to control their blood glucose level.
2 Insulin reduces the amount of glucose in the blood. It accelerates the rate at which the
liver converts blood glucose to glycogen. It makes the body cells take up glucose from the
blood. And it causes some cells to make more protein.
3 There are various reasons why insulin was the first product from genetic engineering
to come on to the market.
• there are many diabetics worldwide and they have to inject insulin every day - so the
demand for insulin is big enough for the pharmaceutical companies to recover their
development costs,
• the number of diabetics is increasing in developed countries,
• insulin is expensive to produce in other ways,
• some diabetics do not respond well to insulin extracted from animals such as pigs -
human insulin is better for them and some people have moral objections to this use of
animals,
• insulin is one of the simplest proteins, and is controlled by a relatively short length
of DNA,
• the supply of insulin from the pancreas of animals such as pigs, sheep or cattle is
limited. Genetically engineered insulin allows supply to be matched to demand.

102 B12 Inheritance
Answers to extra questions on disc
4 The culturing of micro-organisms is easier to control and there are fewer problems
with the quality of the extracted material and continued supply of material.
5 A temperature of 35-40 °C, adequate nutrients and sufficient oxygen for respiration (if
the bacterium is aerobic).
6 The initial research and setting up of the industrial plant is expensive. Hygiene factors
are extremely important and procedures to avoid contamination are necessary.
7 White cells are collected and the gene for interferon is isolated using 'cutting'
(excision) enzymes. The rest of the process follows that shown for insulin.
Completed diagram and notes
A gene provides the instructions for a cell to
do a particular job.
the part of DNA molecule in normal human
cell which controls the production of insulin
DNA strand ==?£=
DNA molecule from
a human cell
Enzymes, acting as chemical scissors, cut the
insulin gene from the human DNA.
gene for human insulin
double strand of
plasmid DNA
'cutting' enzyme
An enzyme cuts the circle of
DNA in a bacterial cell.
A genetic engineer switches genes
from the cells of one type of organism
to the cells of another organism.
The bacterial DNA takes up the fragment of
DNA which includes the insulin gene.
circle of DNA
in a bacterialcell
(called a
plasmid)
bacterium
Bacteria reproduce very quickly. In the right
conditions bacterial cells divide every 30
minutes or so.
When cells divide they make copies of their
DNA, so each new cell has a full set of its
own DNA.
bacteria grown on industrial scale
o)
normal bacterial DNA
Bacteria with the insulin gene produce insulin
in a fermenter.
Other resources
Pathways Sourcebook New life pages 26-7 gives information about genetic engineering.
On disc
The disc includes an extract from the Pathways Sourcebook New Life, pages 26-27. The
disc also has extra information on genetic engineering, for more able students, and the
extra questions 4-7.

B74 Genetic engineering - the issues (H)
B12 Inheritance 103
REQUIREMENTS
Students will need:
activity sheet
library books
audio tape recorder and tape
Notes on the activity
Discussion of some of these issues is at a high National Curriculum level, but they are
relevant to all students. This activity is accessible to all students and allows differentiation
by outcome. The idea of using tapes means that the activity provides students with a
different way of presenting their work which is fun to try. If this is not possible in your
situation you could invite the students to produce a written product (tape script or
magazine article) or a video tape. This might be an opportunity for collaboration between
the Science department and the English department in your school. If time allows, it is a
good idea to provide students with a target audience for their tapes. The tapes could be used
in the classroom with younger students or could be played to parents and governors at an
open evening.
Possible answers to questions
Q Please tell us something about the work you do.
A Here are some actual answers from staff Involved in plant breeding at the John Innes
research centre:
Jonathan Crouch: 'I am trying to produce a variety of oilseed rape which is resistant to
diseases. I travel round the world hunting for wild plants with natural resistance.'
Isobel Parkin: 'I study oilseed rape. I am mapping the genes on the chromosomes and I am
trying to find out more about the way rape reproduces.'
lan King: 'I am running a breeding programme which is trying to develop a strain of
wheat which can grow in salty water.'
Tracey Pittaway: 'I am part of a team which is mapping the genes of the millet plant. We
are trying to find out what the genes do and where they are on the chromosomes.'
Q What is the difference between plant or animal breeding and genetic engineering?
A 'Plant breeders try to produce better crops by the traditional method of crossing one
variety of a plant with another. They might try and combine high yields with disease
resistance. They would do this by taking the pollen from one parent plant and using it to
pollinate the flowers of the other parent plant.
Genetic engineering involves taking the genes from one living thing, say a plant, and
putting them in the cells of another plant. Genetic engineering has only been possible
since scientists began to understand about DNA and the way cells make proteins.'
Q Can you point to any successes of genetic engineering? What are these successes, and
how do they improve our lives?
A 'Genetic engineers have put the genes for making human insulin into bacteria. Now
diabetics inject themselves with pure human insulin instead of insulin extracted from
animals. Genetic engineers have taken a gene from an Antarctic fish and put it into
tomatoes. The tomato plants are more resistant to cold weather and so can be grown earlier
or for longer in cool climates.
Q What is it about genetic engineering which seems to worry the general public?
A 'People worry that genetically engineered plants, animals or bacteria might do more
harm than good. Here are some of the fears which people have:
• a plant with added genes might turn out to be a fast growing weed which was very
difficult to control,
• bacteria with added genes might escape from a laboratory and cause an epidemic of a
new disease,

104 B12 Inheritance
• genetic engineers might start playing around with human genes - perhaps trying to
make super-brainy or super-healthy people.'
Q What can scientists do to help the public understand the benefits and risks of genetic
engineering?
A 'Scientists working on genetic engineering find the work exciting and adventurous,
but they have to remember to explain what they can and cannot do. Some of the fears
come from people who imagine that scientists are much cleverer than they really are. We
have to tell people what we are trying to do in our research and we have to show people
the methods we use.'
Q Do you have any worries about the effects of genetic engineering? If so, what are the
things which you worry about?
A 'My biggest fear is that there will be so much prejudice against genetic engineering
that the politicians will pass laws which stop or slow down our research.'
Q What would you like to see happen in the future with genetic engineering?
A 'I look forward to a new Agricultural Revolution. Many people worry about the
effects of modern agriculture on the environment. They fear the long-term effects of the
fertilizers and pesticides which now vastly increase crop yields. I hope that we can use
genetic engineering to produce new varieties of plants which will make us much less
dependent on chemicals for our food.'
Q Who should control genetic engineering research? Politicians? Scientists? The general
public?
A 'Funding for research comes from industry and from governments. So as scientists we
have to persuade politicians and industrialists that what we do is important and worth
paying for. As with other advances in technology, biotechnology will change the way we
live and how we think about the world. This means that it is important that we debate the
issues in public.'
ScO
2 e consider the power and limitations of science in addressing industrial, social and
environmental issues and some of the ethical dilemmas involved
4 a use a wide range of scientific and technical vocabulary and conventions, and to use
diagrams, graphs, tables and charts to communicate information and to develop an
argument
Other resources
Pathways Sourcebook New life pages 12-13 and 26-7 gives information about genetic
engineering.
On disc
Pathways Sourcebook New Life pages 12-13 and 26-27.
B75 Cloning a cauliflower (H)
REQUIREMENTS
Students will need:
activity sheet sides 1 and 2
test-tubes plugged with non-absorbent
scalpel (see safety note 1)
cotton wool and capped with aluminium
cutting board
foil, each with 23 cm3 of plant tissue
blunt-ended forceps growth medium (see note 1)
sterile Petri dish
small plant pots
metal forceps (see safety note 3)
Bunsen burner and mat
eye protection

B12 Inheritance 105
Access to:
piece of cauliflower curd (the white part)
cloth soaked in bleach (see safety note 2)
ethanol (see safety note 3)
bleach solution in small beaker (see note 3)
sterile distilled water in three small beakers
a well lit draught-free place
growth medium (see note 1)
aluminium foil
cotton wool
peat
clingfilm
a video about practical microbiology
Notes:
1 To make 1 litre of plant tissue growth medium dissolve granulated sugar (20 g),
Murashige and Skoog medium (4.7 g) and agar (10 g) in 725 cm3 distilled water. Add in
25 cm3 kinetin stock solution (see note 2), then dispense into test tubes. About 23 cm 3
per tube are needed. Plug the tubes with non-absorbent cotton wool and cap with
aluminium foil. Autoclave at 121 °C for 15 minutes in a pressure cooker. When cool, the
tubes may be refrigerated until needed.
2 Kinetin stock solution contains 0.1 g kinetin in 1 litre of distilled water. Kinetin does
not dissolve readily in water, but adding one or two pellets of sodium hydroxide helps.
Store the stock solution in a refrigerator at 4 °C. Wear plastic gloves when handling
kinetin.
3 A suitable bleach is 20% Domestos solution, which consists of chlorate(I) solution
with added detergent.
Safety notes
1 Be vigilant while your students are using scalpels. Check that they dispose of waste
cauliflower correctly.
2 Students should take care using bleach solution, especially those with sensitive skins.
Ensure all splashes on the skin are quickly and thoroughly washed off. Eye protection
must be worn. Sterile working is crucial to success.
3 Take great care with ethanol, keeping the stock bottle well away from naked flames.
Ensure that only very small volumes are used for sterilizing metal forceps. Dipping
forceps in ethanol and burning off the solvent heats the surface of the instruments to 70 °C
and kills any contaminating organisms. Check that students do not heat forceps directly in
a flame. Burning ethanol is hazardous, so consider using pre-sterilized plastic forceps.
Notes on the activity
This challenging practical is based on information in a booklet about practical
biotechnology from the National Centre for Biotechnology Education (see Further
information about inheritance). See also number 13 in the ASE's Experimenting with
Industry series. In view of the attendant hazards this is an activity we would only
recommend for groups of trustworthy students likely to be able to master the practical
skills involved.
You may find it helpful to let your students watch a video about practical
microbiology which demonstrates aseptic techniques (see under Further information).
Cauliflower is ideal for plant tissue culture in schools because it is readily available,
robust enough to withstand being handled by students, and grows rapidly. Growth can be
seen within a fortnight and plantlets are ready for transplanting within 12 weeks.
Keep the tubes with the explants in a warm, light place. Growth should be visible in
10 days, and any contamination will also be obvious in this time. If the explants do not
grow, the likely reason is that the bleach was not fully rinsed from the plant tissue.

106 B12 Inheritance
Answer to question
Cut small pieces of
tissue (explants)from
the plant
Sterilize the
explants in
bleach
Wash 3 times in
sterile water to
remove bleach
Rinse off growing
medium and plant
out in moist peat
Cover tubes and keep
in a warm, light place
for several weeks
Transfer to a sterile
growing medium in
tubes
ScO
2 a consider ways in which science is applied and used, and to evaluate the benefits and
drawbacks of scientific and technological developments for individuals, communities and
environments
Other resources
NCS Biology Chapter B22.
B76 Plant and animal clones (H)
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
Tissue cultures show that single cells of carrot phloem can grow into whole new carrot
plants when kept in suitable containers and supplied with the proper nutrients and plant
growth substance IAA. For continued cell division, cytokinins are also required.
Answers to the questions
1 A new plant produced by cloning has chromosomes identical with those of the parent
plant. So clones grown under the same conditions are identical because they grow from
cells which are genetically identical. The nuclei are produced by mitosis.
2 The advantages of cloning in agriculture are that a lot of plants can be produced very
quickly and cheaply from a few plants. A new strain of plants can be exploited quickly and
efficiently. Also a relatively easy way of eliminating viral disease. The cloned tissue is
taken from young healthy parts of the plant which the virus has not had the chance to
infect (apical meristems are usually free from infection).
Cloned plants are genetically identical. They ripen uniformly, which makes harvesting
easier.
Some people worry about farmers sowing enormous acreages of genetically identical
crops. They fear that pests will sweep through such fields quickly. A population of
genetically identical organisms is highly vulnerable both to pests and to environmental
changes.
3 Gardeners have used traditional methods to clone plants, including:
• taking cuttings from stems or leaves,
• layering - tying a stem down to the ground, so that it sends out roots,
• grafting onto 'root stock',
• using vegetative organs, e.g. potato tubers, corms, bulbs etc.
4 Traditional methods of cloning take quite large pieces cut from plants and grow them
in soil or potting compost. Modern methods of tissue culture start with very small pieces
of plants -just a few cells, or even single cells. Biotechnologists begin by growing the

B12 Inheritance 107
cells in solutions which contain all the nutrients needed for growth, taking great care to
keep out microbes.
5 Tissue culture is a more difficult and complex technique than taking cuttings or
grafting, but it is a more efficient way to produce plants in large numbers. On a small
scale it is more expensive than gardeners' methods, but on a large scale it is cheaper.
6 a It is more difficult to clone animals than plants because generally animals are more
complex organisms. The cells in animals are more clearly differentiated at an earlier stage
of development. Any plant cell will develop into a whole new plant under the right
conditions. Animals have to grow from an egg cell.
b It is more difficult to clone mammals than amphibians because the egg cell is very
much smaller.
7 The baby rabbit will resemble rabbit 1. The egg has developed under the control of the
DNA in the chromosomes from liver cells of rabbit 1. The baby rabbit has inherited all its
genes from rabbit 1.
8 a The offspring are not all the same with normal animal breeding. A farmer cannot be
sure that young animals will inherit all the desirable features of their parents. Cloning an
animal with special features (such as rapid weight gain or high milk yield) would allow a
farmer to produce many genetically identical animals with the same features.
b If all the animals in a herd or flock are genetically identical they will be equally likely
to catch a disease or be harmed in bad weather. In time repeated cloning could easily lead to
a loss of genetic variety in farm animals. Then it would be difficult - perhaps impossible
- to breed new varieties with features needed to thrive under new conditions.
9 In 1982 the British government set up a committee, chaired by Mary Warnock, to
consider new developments in medicine and science affecting human fertilization and the
development of embryos. The committee was asked to consider the social, ethical and legal
implications of these developments. One of the difficult issues is to decide when a
developing embryo becomes an individual with human rights. Hardly anyone regards
sperm cells or unfertilized eggs as having human rights. Almost everyone believes that a
newborn baby has human rights. The problem is where to draw the line in between.
Opponents of any research into human embryos think that a fertilized egg has the same
right to life as a child or adult. Others believe that the benefits of embryo research are such
that experiments with embryos should be allowed for a few days after fertilization - up to
the point at which it is clear that the developing ball of cells is likely to continue to
develop into a person. This is about 14 days after fertilization. It is possible to remove a
cell from a very early embryo. The embryo is then frozen. The 'cell sample' is allowed to
grow on so that genetic tests are possible. If the 'cell sample' is healthy, then the donor
embryo is healthy. It can then be implanted into the mother to develop in the normal way.
PCR techniques make it possible for DNA from a very small number of cells to be
copied. This may well be a future option. The Warnock committee was in favour of
limited embryo research intended to help people to have healthy babies and to avoid
genetic diseases.
The committee and the government were quite sure that it is ethically wrong to
attempt human cloning or any other method for creating people with special
characteristics. Following the report from the committee, the government proposed a law
to make human cloning a criminal offence.
ScO
2 a consider ways in which science is applied and used, and to evaluate the benefits and
drawbacks of scientific and technological developments for individuals, communities and
environments
2 e consider the power and limitations of science in addressing industrial, social and
environmental issues and some of the ethical dilemmas involved
Other resources
NCS Biology Chapter B22.

108 B12 Inheritance
B77 Selective breeding
REQUIREMENTS
Students will need:
activity sheet
Access to:
scissors for cutting paper
glue (solvent free)
Notes on the activity
The development of different breeds of cattle provides a good example of selective breeding
for particular characteristics. Jersey cattle not only yield creamy milk but they mature
quickly, and are useful for improving native cattle in regions where heat tolerance is needed.
The Highland breed is very hardy, often being grazed in mountainous areas, but is slow to
mature. There is some variation in Friesian (Holstein) cattle: the North American type
being primarily bred for milk whereas the Dutch type is mainly used for meat. The Hereford
is a hardy breed which matures early and adapts itself to a wide range of climates from near
Arctic conditions in Canada to the Australian outback. The Simmental is widely bred in
Europe and, although mainly used for meat, can produce high milk yields.
Continuing inbreeding of animals and plants eventually reduces the diversity of the
gene pool and can lead to loss of productivity and decreased resistance to disease.
Outbreeding, which is especially useful for plants, involves crossing individuals from
genetically distinct varieties or strains, that are homozygous (pure breeding) for the required
characteristics. The results from such crossings, which are called F! hybrids, exhibit
advantages such as increased fruit size and increased resistance to disease. Some commercial
F! hybrids do not exhibit significant increase in yield, but have the advantage of genetic
consistency.
Match the pictures and captions as follows:
A-l
B-4
C-3
D-5
E-2
Answers to questions
1 The Simmental is bred in many places in Europe. Although kept mainly for meat, it
can produce high milk yields.
2 Highland cattle are hardy. This hardiness can be passed on to other cattle by a planned
breeding programme.
3 a Bread wheat has more seeds and the seeds are larger than the seeds from wild wheat.
Bread wheat has a thicker stem than wild wheat.
b A growing wheat plant forms leaves, a stem and the seed head. Breeding can increase
the yield of the seeds by developing varieties which concentrate growth on the seeds and put
less into forming the stems which end up as straw which is no longer valuable for
thatching. Developing varieties with shorter, stiffer stems also helps to prevent the wind
and rain from knocking down the growing crop before harvest time, now that the ears are so
heavy. Also the seeds must not be dispersed from the stem before they are ripe for
harvesting.

B12 Inheritance 109
Name of breed
Dachshund
Siberian husky (Arctic husky)
Pekingese
Whippet
German shepherd (Alsatian)
Rottweiler
Labrador retriever
Purpose
Hunting badgers (also foxes and
rabbits)
Sleigh dog
Companion/pet
Hunting/racing
Tending flocks of sheep
Originally bred as guard dogs and to
herd cattle to market
Sports dog, for finding and bringing
back game shot by owner
Characteristics developed by
breeding
Elongated body
Short legs with large paws for
digging
Powerful jaws
Stamina
Powerful but quick
Dense, warm coat
Small
Long silky coat
Loud yap to warn about strangers
Fastest sprinting dog
Streamlined shape
Short coat
Deep rib-cage
Good eyesight (used instead of nose)
Very responsive to training
Good at herding
Observant and watchful
Good stamina
Strong, muscular,
Loyal
Prepared to defend their owner or
territory
Good sense of smell
Stamina
Dense, waterproof coat
Powerful tail (used as a rudder when
swimming)
ScO
2 a consider ways in which science is applied and used, and to evaluate the benefits and
drawbacks of scientific and technological developments for individuals, communities and
environments
Other resources
Pathways Sourcebook New Life pages 10-11 gives information about artificial selection
and cattle, and 12-13 gives information about plant breeding.
Darwin's Origin of Species has many references to domesticated species.
Books with pictures and descriptions of breeds of dogs will be found in the public library
and probably in the school library too.
B78 Potato cyst eelworm and potato blight (H)
Notes on the activity
There are opportunities for links with History. At the end of the 16th century Sir Walter
Raleigh brought only a few potato tubers back from America to Ireland. The gene pool,
which provided the ancestry for all the potatoes of Europe, was therefore extremely small.
These plants were propagated vegetatively, producing a clone of identical plants. If
one plant was affected by disease, it would quickly spread through the whole area.
This would be a good place to review the differences between vegetative and sexual
reproduction.

110 B12 Inheritance
There is also a chance to discuss the relative merits of breeding resistant varieties,
using pesticides and using biological control (see below).
The life cycle of the potato cyst eelworm
In spring newly hatched
nematodes enter the root
and fed on it
About 10% of the eggs
in each cyst hatch
each year.
Females (fewer
than males) feed
and become very
fat The body
sticks out of the root
the head stays
inside.
Males (more
numerous than
females) leave
the root to
fertilize females
from the outside,
Overwintering.
If left in the soil,
the cyst darkens and
falls away from the root
Fertilization.
The fertilized female's
body, containing
500 eggs, becomes
even more swollen.
This is the cyst
Answers to selected questions
2 The idea is to put over the general concept of transferring genes without going into
methods like protoplast fusion or anther culture. You may have to examine the life cycle
of the potato. Breeding done by pollination will involve planting seeds (not the same as
'seed potatoes' - that is a form of cloning) and then collecting the tubers grown from the
seeds. From then on cloning methods are possible.
3 Methods involving pollination will not work.
4 The pollen would carry one copy of all the genes of the wild plant.
5 Take the F, from the cross between wild and cultivated types and cross them to the
cultivated variety. Check the offspring of this cross for resistance and cross them to the
parental cultivated line again; check the offspring for resistance and cross them to the
parental cultivated line; and so on, repeating this for five or six generations.
ScO
1 b use and bring together information from a range of secondary sources
2 b use scientific knowledge and understanding to evaluate the effects of some applications
of science on health and on the quality of life

B12 Inheritance 111
Other resources
Pathways Sourcebook New life pages 10-13 gives information about artificial selection.
Further information
Hobhouse, H. Seeds of change. The story of the first winter of potato blight in Ireland.
Papermac, 1992
Wilson, A. The story of the potato Henry Doubleday Research Association, 1993.
National Centre for Organic Gardening, Ryton on Dunsmore, Coventry, Warwickshire
CV8 3LG.
Tudge, C. Food Crops for the Future, Blackwall, 1988, ISBN 0-631-15082-X.

Nuffield Biology Section B13
Evolution
Context
In this section the importance of the fossil record in providing evidence for the evolution
of different species is considered. The work of Darwin and Wallace is summarized.
Students should appreciate that genetic variation may give rise to organisms which have a
selective advantage and that these organisms may reproduce and alter the gene frequencies
of future populations. Organisms which are at a selective disadvantage may become
extinct. The principle of natural selection should be illustrated by a number of examples
(e.g. sickle-cell anaemia, peppered moths, antibiotic resistance, banded snails etc.).
B79 Fossils
REQUIREMENTS
Students will need:
activity sheet
textbooks
Notes on the activity
There are various ways you could organize this activity in the classroom. You could give
each student a photocopy of the activity sheet to cut up and stick bits into their written
record. Alternatively, students could use the sheet as a prompt and produce their own
continuous piece of prose in response to the first activity. They could copy the writing and
drawings for the second.
Fossils are organic remains, buried by natural processes and permanently preserved.
To be preserved, animals and plants have to end up in places where they can be buried
before disintegrating or being eaten. Only very occasionally are remains of soft parts found
in rocks. Usually it is the hard parts, the skeleton or the shell of an animal, that are
preserved. Often the fossil is not the original material of which the animal was made - the
bone is gradually replaced by other minerals, so that what remains is like a cast of the
original. Sometimes the animal itself is not found, and only its tracks, or burrows it made
in the sea floor, survive in the rocks.
Countless creatures and plants must have lived on Earth without leaving a trace. So
fossils do not tell the whole story of life - they are more like clues which can help to
build up a picture of what organisms looked like and how and where they lived.
Match the text and pictures as follows:
1 -C
2-A
3-B
Opportunities for co-ordination
C44 and C47 refer to fossil-bearing rocks.
Other resources
Pathways Sourcebook New life pages 34-35 gives information about fossils.

B80 A theory based on natural selection (H)
B13 Evolution 113
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
This activity uses a discussion technique based on concept mapping. Point out to students
that there is no right outcome for this activity. It can be worthwhile to ask groups of
students to present and justify their maps to the rest of the class.
Explanation of the terms
Inheritance
There are many characteristics which are passed on from one generation to the next. They
are inherited. Puppies grow up to be dogs and bitches. Kittens grow up to be cats. A
fertilized egg contains all the information in its chromosomes which it needs to develop
and grow into an adult organism.
Natural selection
The members of a species which are well adapted to their environment are the ones which
are most likely to survive long enough to reproduce. Gradually their descendants make up
a larger proportion of the population. Other, less successful, forms become less common
and may die out. The changing proportions of speckled and dark varieties in the
populations of moths around Manchester illustrate how this can happen (see B83).
Number of offspring
All species can produce more offspring that the minimum needed to reproduce themselves.
If they produce more than the minimum and enough of the offspring survive, the
population increases. If they produce too few the species declines and may become extinct.
See Teachers' Notes on B81, which shows why a pair of frogs must produce over 300
eggs to ensure the survival of their species.
Origin of species
A species is a group of organisms which can interbreed with each other and produce fertile
offspring. The modern theory of the way in which animals and plants change and produce
new species is based on Darwin's theory of natural selection.
Struggle for existence
All organisms compete with members of the same and other species for resources such as
food, and with members of their own species for a mate.
Survival of the fittest
In this case the 'fittest' is the organism which can best survive the environment in which
it lives - as biologists put it, the one which is best adapted. Organisms which are well
adapted to living in a habitat are the ones which survive long enough to reproduce. More
successful varieties of the species make up a growing proportion of the population.
Variation
Variation is very important in a population of organisms. There is quite a lot of variation
within most populations. This is often a good thing. Variation can help a species survive
when the environmental conditions change. One variety in the population may be better
adapted to the new conditions and ensure the survival of the species as a whole.
Other resources
NCS Biology Chapter B23.
Pathways Sourcebook New life pages 28-9 gives information about mutations.

114 B13 Evolution
On disc
Extracts from Pathways Sourcebook New Life, pages 36-37 are on disc.
B81 How many offspring?
REQUIREMENTS
Students will need:
activity sheet
Access to some of the following:
annual or biennial weeds and garden plants (see activity sheet)
insect eggs on a leaf (e.g. butterfly eggs on cabbage)
fruits or vegetables with seeds (e.g. tomato) (see safety note 1)
For the suggested practical work students need:
hard roe of herring, smoked roe may be easier to find than fresh or frozen (see safety note 1)
Petri dish
mounted needle (see safety note 2)
reference books
Access to:
balance
click counter (optional)
Safety notes
1 Dispose of waste organic material with care. Ensure that students wash their hands
after the activity.
2 Students must take care when using sharp instruments.
Notes on the activity
The activity introduces one of the key parts of Darwin's thinking about evolution: that
organisms are able to produce vast numbers of offspring of which only a few survive to
breed. The activity also gives students the chance to practise the skill of making order-ofmagnitude
estimates. You may need to explain to students the value of estimates of this
kind and encourage them not to waste time pursuing an over-precise right answer.
Encourage different groups to explore different examples to produce a wide range of
estimates. Students are likely to be amazed by the number of seeds they find in a tomato,
for example.
Although Darwin's theory is intended for students working at the higher level, all
students will be able to enjoy this activity.
Estimates of animals
Here is an example of an estimate. A dog might have about 6 puppies to a litter and
reproduce 8 times in its lifetime. That makes 48 puppies. The estimate is tens.
Order of magnitude estimates:
• dog - tens
• herring - millions
• stick insect - hundreds
• butterfly - tens
• bird - tens
• frog - hundreds
• chicken - tens
• cat - tens
• mouse - tens
• hamster - tens
• cows - tens

B13 Evolution 115
The fish which lays the largest number of
eggs is the ocean sunfish. It may lay up to
300 000 000 eggs at one time.
Here is a way to find the number of eggs in
the hard roe of a herring.
a Find the mass of the hard roe (eggs) of a
herring.
b Weigh out 1 g of the eggs.
c Put the eggs in a dish and just cover them
with water.
d Use a mounted needle to separate the eggs.
Count the number of eggs in 1 g.
e Multiply the mass of the whole roe (from a)
by the number of eggs in 1 g. This gives the
number of eggs in one roe. A female herring has
two roes, so double the number to get the number
of eggs produced by the herring in one season.
Petri dish
herring roe
mounted needle
If you do this,
wash your
hands
afterwards
Estimates of plants
Pea pods contain about 20 seeds. A pea plant is an annual, which means that it lives for
one season, so it flowers and sets seeds only once. There might be 20 pods on a plant.
That makes 400 peas. The estimate is 'hundreds'.
• pea - hundreds
• lupin - hundreds
• broad beans - tens
• geranium - tens
• groundsel - hundreds
• dandelion - hundreds
• tomato - hundreds
Answers to questions
1
caterpillars killed
by disease
caterpillars killed by parasites
caterpillars eaten by birds
pupae killed by disease
pupae killed by parasites
healthy adults
2 Out of the 300 or so eggs laid by a female frog, some are not fertilized by the male's
sperm, which he releases into the water at the same time as the female lays her eggs.
• Some fertilized eggs fail to develop. The rest become tadpoles.
• Some tadpoles are eaten by dragonfly nymphs and small fish. The rest become adult
frogs.
• Some adult frogs get eaten by herons and pike.
• Some adult frogs die from parasite infections.
• Some adult frogs don't survive hard winters when they hibernate in the mud at the
bottom of ponds.
• Some adult frogs get killed on the road on their way to the spawning ponds.
• Two or three may reach adulthood and spawn themselves.
3 The plant produces 2 seeds each year, so after n years there are 2" plants.

116 B13 Evolution
Number of years
1
2
3
4
5
6
7
8
9
10
•
20
Number of plants
2' = 2
2 2 = 4
23 = 8
24 =16
2 5 = 32
26 = 64
27 = 128
28 = 256
29 =512
2 10 = 1024
•
220 = 1 048 576
Most plants produce many more than two seeds each year. In fact they produce
enormous numbers, but only very few of these survive the hazards of growing to maturity.
The common field poppy produces about 17 000 seeds on each plant. They are small
enough to be blown away by the wind. Many of them land on places where they cannot
germinate. About 3000 seeds from each plant differ from the rest and will only germinate
after several months or even years - whatever the conditions. Seeds will not germinate if
they are washed too deep in the soil. These seeds will only begin to develop into new
plants if brought to the surface by digging or ploughing - for example in cornfields and
beside new roads.
On disc
Extracts from Pathways Sourcebook New Life pages 36-37 (under B80).
B82 Darwin's Century (H)
REQUIREMENTS
the top part of the activity sheet and one catalogue extract
alert your librarian
large paper for posters
supply of bold felt tip pens
Notes on the activity
The students need some knowledge of what the Darwin-Wallace theory means.
This activity is intended to give pupils an opportunity to address the nature of
scientific ideas - specifically how scientific controversies can arise from different ways of
interpreting empirical evidence.
It is a good opportunity to use IT to collect and handle scientific information and to
make use of the school resource area.
The suggested way of presenting this activity is to cut up the sheet and distribute
single extracts around the class. The pupils then pair up and carry on as instructed. There
are more pro-Darwinian slips than anti so you will need to distribute sufficient Agassiz
and Cuvier slips to ensure matches can be made. You may also need to warn librarians!
It is interesting to note that Richard Owen is always described as the only man
Darwin hated, and Darwin did say Owen should be ostracised by every naturalist in
England. Yet the unpublished letter (from which the extract on the activity sheet is taken)
is remarkably generous in its appreciation of Darwin's theory. It was written at a time
when monuments to Darwin were being discussed. It was one of the major discoveries of
the sale at Sotheby's.
Owen coached Bishop Samuel Wilberforce before the debate on evolution with
Thomas Huxley. This 'change of heart' after Darwin's death could provide another way
into the activity. It obviously leads onto the answer to the question about Wilberforce

B13 Evolution 117
and the British Association debate in 1860 at Oxford. Part of the argument Huxley and
Wilberforce had, could usefully form the basis of pupils explaining it in their own words.
A useful part of it is quoted in Nuffield Biology Text Year V The Perpetuation of
Life 1967 p 201.
When Wilberforce in 1873 fell on his head in a riding accident Huxley said 'For once
reality and his brain came into contact, and the result was fatal.'
At the 1959 Darwin centennial celebration at Chicago University a musical was
performed. The actor playing Huxley sang the words:
'I don't see that the Bishop has reason to sneer,
And I have no wish to abuse him;
But taking this line,
If I had to incline
Toward ape or divine,
Would I choose him?'
An easily obtained summary of all the controversy is to be found in Chapter 11 of
Darwin a Life in Science by M. White and J. Gribbin.
Depending upon the strength of your resources an extension activity might be -
'What modern day books could usefully form the basis of a collection about evolution?'
Another suggestion might be to look for modern day controversy which surrounds
Darwinian theory. A good example is the application of Darwinian theory to diseases as
outlined in Evolution and Healing -The New Science of Darwinian Medicine.
Answer to question
The debate between Bishop Wilberforce and Thomas Huxley referred to in the main notes,
marked the turning point of the controversy over evolution in Britain. Huxley continued
to defend Darwin, earning the name 'Darwin's bulldog'.
ScO
3 a develop their understanding of how scientific ideas are accepted and rejected on the
basis of empirical evidence, and how scientific controversies can arise from different ways
of interpreting such evidence
Other resources
The Pathways Sourcebook New Life, pages 36-37, provides extracts from Darwin's
Origin of the Species.
On disc
Extracts from Pathways Sourcebook New Life pages 36-37 (under B80).
References
Browne, J., Charles Darwin Voyaging Volume 1 of a Biography, Jonathan Cape, 1995,
ISBN 0 224 04202 5 and Volume 2 when it is published
Darwin's Century The Jeremy Norman Collection The Catalogue of the sale on 11
December 1992. Sotheby's 34-35 New Bond Street London W1A 2AA
Nuffield Biology Text Year V The Perpetuation of Life , p 201, The Nuffield
Foundation, 1967
Nesse, R. and Williams, G. Evolution and Healing The New Science of Darwinian
Medicine , Weidenfeld and Nicolson, 1995, ISBN 0 460 86140 9
White, M. and Gribbin, J., Darwin A life in Science, Chapter 11 'Battles with Bigotry'
Simon and Schuster, 1995, ISBN 0 671 713 531

118 B13 Evolution
B83 Selection in action (H)
REQUIREMENTS
Students will need:
activity sheet
textbooks with photos of peppered moth and banded snails
Notes on the activity
This activity will allow students to explain 'fittest' in terms of fitting into an ecological
niche, rather than being physically fit.
They might also take the opportunity to revise some basic ideas about food chains and
predator-prey relationships.
The next activity, B84, gives students a chance to use a model of predator/prey
relationships.
Activity B85 looks at evolution in the flu virus. You could thus discuss different
time-scales for evolution:
flu virus -1 year
peppered moth - 10 years
horse (Equus from Eohippus) - 50 million years
Answers to questions
1 A possible explanation is that the dark form of the moth has a gene for colour which
has changed (mutated).
2 One of the biggest problems of the theory of natural selection is finding proof for it.
When scientists examined the changes in the proportions of speckled and dark moths they
thought that it was important evidence to support the theory.
Lichens grow on tree trunks. They make tree trunks look a speckled grey colour. They
are very sensitive to air pollution. Air pollution kills the lichens, the dead lichens turn
black, and soot in the air makes the tree bark darker.
A tree in an area free of air pollution has plenty of lichens on its trunk. The speckled
form of the moth is camouflaged against this background. Any dark moths are easier to see
and more likely to get eaten by the birds.
Air pollution from burning coal killed the lichens in the Manchester area and
blackened tree trunks. As a result the black form was better camouflaged. The birds ate
more of the speckled form.
3 The thrush's anvil is a stone. The thrush smashes the shell so that it can eat the body
of the snail.
4 Yellow snails are better camouflaged when new leaves and grass have grown in the
spring.
5a Snails with no bands or just one band are more common in woodland.
b Yellow snails with several bands are more common in grassland and hedgerows.
6 The percentage of yellow shells is higher in hedgerows and grassland. This suggests
that the numbers of yellow snails would increase if there was a decrease in the amount of
woodland.
Other resources
NCS Biology Chapter B23.
Pathways Sourcebook New Life page 40

B13 Evolution 119
B84 Using models to explain selection (H)
REQUIREMENTS
Activity 1
margarine tubs containing vermiculite coloured with food colouring
long grain rice (dyed in assorted colours using food colouring)
forceps
stop watches
Activity 2
metric tape measure (10 m long) or string knotted at 1 m intervals
4 wooden pegs or skewers
part cooked spaghetti (not too soft) in two colours - preferably one that is easily seen, e.g
yellow and the other green
clipboards and metre rulers
Notes:
Activity 1
Vermiculite can be stained with a strong solution of food colouring. Yellow, green, red and
blue dyes are quite good. The staining is best done by putting the dye and vermiculite in a
polythene bag, sealing it with a rubber band and shaking it. The vermiculite is then spread
on newspaper and dried. Grains of long grain rice (uncooked) can also be stained and dried in
a similar way. It is wise to prepare quite large quantities since it is a tedious process.
Various combinations of vermiculite and rice grains can be tried. Obviously green grains in
green vermiculite are harder to see than red grains, but you can experiment with say, blue
and yellow grains against a green background. Pupils will find that some colours blend
with certain backgrounds and not others. Parallels between this experiment and the Peppered
Moth or Banded Snail examples are fairly obvious.
An interesting variant is to make students try the experiment once and then repeat it
using a coloured filter over the eyes (or try it under different coloured lights).
There are a number of obvious 'errors' in this experiment. It takes no account of
heterozygosity for example. It assumes that prey is located only by colour and so on, but it
does give an opportunity to obtain interesting data which should stimulate discussion.
You will need to be sensitive to students who are red-green colour blind.
Activity 2
It is actually better to use coloured pasta than to try using food colouring which tends to
wash off or bleach in rain or strong sunlight. To make sure the two colours are placed
randomly, a coin could be tossed. The local birds are usually quite obliging at removing
pasta within a day or two. Again there are a number of 'errors'. The taste of the different
types of pasta may vary and, if it rains, the dye may wash off. Interesting results are
obtained if the pasta is placed on a different surface, e.g. a tennis court or bare ground. The
pattern of predation might also indicate whether birds 'graze' areas of ground or whether
they are more selective.
B85 New types of flu
REQUIREMENTS
Students will need:
activity sheet
diagram sheet

120 B13 Evolution
Notes on the activity
This is quite a demanding activity which requires students to interpret data and represent it
on a map. (Note that this is a map of Europe after World War I, and the borders of some
countries are different from those of today.)
Answers to questions
1 and 2 Flu is caused by a ;
virus. A person doesn't gain
permanent immunity after
catching flu. The problem is
that the virus keeps changing its
genetic make-up. Mutations
mean that the pattern of proteins
on the outside of the virus is for
ever changing. The immune
system works by making
antibodies which recognize the
proteins of the virus. Antibodies
cannot identify and destroy a
new form of the virus when its
pattern changes. As a result, a
new form of the virus can spread
rapidly in the right conditions.
Diffusion of flu into Europe, spring 1918
4 In 1918 World War I was coming to an end. Large numbers of people in the armed
forces were on the move. Troops were shipped from the USA to Europe to help with the
fighting. The civilian population was living under stress with food shortages and a poor
diet.
5 The first European outbreaks were all in ports. The first UK outbreak was probably in
Glasgow - one of the main ports where ships from the USA docked to unload people in
the armed services. On the continent the spread of the disease followed the main lines of
communication.
6 a It seems that the second outbreak was caused by a new form of the flu virus. People
who were immune to the earlier form were not immune to the new variant.
b Brest is a port. It was a big transit centre with thousands of troops disembarking on
their way from the USA to the battle front. At the same time ships were leaving for
destinations all over the world to take troops home or to collect war goods. Shortly after
the second wave began in Europe, there were outbreaks of the disease in Boston,
Massachusetts; and in Freetown, Sierra Leone - one of the major African ports. The
outbreak spread rapidly across the world, reaching San Fransisco and Bombay before the
end of September. It was kept out of Australia until early 1919.
7 Measures might include:
• ensuring that any ship with a case of flu on board is not allowed to dock for a week,
and then keeping passengers and crew in isolation for a fortnight,
• sterilizing ships before they dock,
• obliging people who have been in contact with the disease to wear face masks until it
is clear that they are not infected.
The first case in New Zealand was reported in October. The Australian government
enforced strict regulations and kept out the disease until January 1919. This gave the
medical services time to prepare. There is some evidence that the longer an epidemic goes
on, the weaker the virus becomes. In Australia at least 13 000 people died (a death rate of
0.25%). In New Zealand the death rate was 0.5%, while in some parts of the world the death
rate reached 2.5% or more.

B13 Evolution 121
Other resources
The Pathways Sourcebook New Life, pages 38-39 gives information about evolution in
microbes.
On disc
The Pathways Sourcebook New Life, pages 38-39 gives information about evolution in
microbes.

Nuffield Biology Section B14
The impact of human activities
Context
Most students are interested in and concerned about environmental issues such as pollution
and loss of species through extinction. These affect our quality of life. This section
examines the biological principles involved.
Fieldwork - planning and safety
Fieldwork activities are an important and enjoyable part of any environment course and can
be appreciated by all students whatever their National Curriculum level of performance.
We hope that you will be able to give your students some 'hands on' experience of
organisms in their environment. Fieldwork gives you an opportunity to encourage a
respect for living things and environments. You can make use of school grounds, rural
science units, parks, cemeteries and the other pieces of 'spare habitat' available to every
school, even in inner city areas.
Successful fieldwork has to be planned well in advance. Even work within school
grounds may require liaison with colleagues. For instance, if you want to use the school
field you should check with the PE department first.
The programme of study for Sc2 specifies that, at Key stage 4, students should make
a more detailed and quantitative study of a habitat, including investigations of the
abundance and distribution of common species, and ways in which they are adapted to their
environment. The programme also states that students should approach current concerns
about human impacts on the environment through fieldwork.
Fieldwork in a local park
Here is a description of two 'field days' organized by a science department in an 11-18
comprehensive school towards the end of the summer term. The two days became a
recognized part of the school calendar and were scheduled a year in advance. See the notes
on safety considerations during fieldwork on pages 3—5.
Notes on the activity
The days involved a team of teaching staff, technicians and post-A level students working
with all the year 10 science students. The aim was to investigate the factors which
influence the fauna and flora in and around a stream running through a park about a mile
away from the school.
Students were carefully briefed during one or two preparatory periods, then the teachers
took them out into the park on both mornings and returned to the lab in the afternoons for
further practical investigations, identification of specimens and writing up the results.
In two mornings groups of students can study the following:
• the rate and direction of flow of the river or stream,
• evidence of silting and succession,
• mapping part of the river to show the depth,
• temperature variations in and around the stream,
• sampling and identifying organisms at regular intervals,
• a belt transect from the river bank,
• use of quadrats and a belt transect to study the distribution of plants near a path,
• identification of trees,
• observation of insects (especially on a sunny day),
• evidence of human impact on the area.

A detailed plan helps students to achieve more. Assign activities to small teams of
staff and helpers who brief the students and supervise their work. Establish a circus of
tasks and a timetable so that groups of students move round the circuit at regular intervals.
REQUIREMENTS
For field days like this, students may need access to:
a map of the area
nets
plastic dishes
a long length of string with marks at 0.5 m intervals
stop clocks or watches
quadrats
tape measures
metre rules
plastic buckets
hand lenses
thermometers (or temperature sensors with portable data loggers)
light meters (or light sensors with portable data loggers)
identification keys
clipboard inside a clean polythene bag (with the sealed end held by the clip, the bottom
end open)
B14 The impact of human activities 123
Fieldworkinawoodorcopse
A small clump of trees, copse or small area of woodland can provide a focus for several
investigations. The overall aim is to investigate the influence of the tree canopy on other
organisms. Students can:
• map an area showing the positions of the trees,
• choose and identify a tree,
• measure the circumference and calculate the diameter,
• measure the height of the tree using a clinometer,
• map out on a grid, by making measurements, the extent of the canopy and its shape,
• observe how the leaves are arranged in the canopy,
• measure and plot the light intensity in various areas,
• identify and map out the other plants under the canopy,
• search the leaf litter for organisms and identify them,
• sample insects by catching them, e.g. with a sweepnet, pooler or pitfall trap,
• look for evidence of other animals,
• observe the same tree at intervals over a period of months.
B86 Patterns in the distribution of a simple plant
REQUIREMENTS
Each group of pupils will need:
clipboard
graph paper
paper
pencils
quadrat, 10 cm2 (made from transparent plastic)
string, marked at 10 cm intervals
Access to:
trees close to the school grounds

124 B14 The impact of human activities
Notes on the activity
The procedure is detailed on the worksheet. It is important that pupils are shown exactly
what Pleurococcus looks like before they attempt to study its density on the tree trunk.
Much of the success of this exercise depends upon the pupils' ability to estimate sensibly
the percentage of bark covered by the protist.
B87 Investigating plant populations
REQUIREMENTS
Depending on their investigations, students may need:
activity sheets including the techniques sheet
quadrats, or cardboard and scissors to make them (see note)
thirty-metre tapes
light meters or light sensors
Access to:
a counting device using a push button (optional)
graph paper
calculators
identification keys
Note:
You may decide to provide ready-made quadrats. Alternatively students can make their own
from card. Home-made quadrats are less durable but are biodegradable if mislaid!
Notes on the activity
The activity sheets include prompts to suggest investigations but it is left to students, to
come up with particular questions on which to base their inquiries. You will have to
assess what is feasible in the locality of your school given the resources available.
You can ask students to come up with ideas for a random sampling strategy with
quadrats. They can use random numbers to determine the number of paces to take in a
given direction and the toss of a coin to decide whether to turn to the left or the right
before taking more paces.
When counting plants they will have to decide whether to count leaves or roots. What
do they do if leaves overlap the edge of the frame? Students will have to decide on a rule.
With students aiming at higher levels, you may decide to encourage a more rigorous
approach to random sampling and a more formal statistical treatment of results with an
analysis of errors in techniques.
It is difficult to represent adequately the size of organisms on the activity sheets. We
have used a system which is consistent but which, we know, has its limitations. We think
that this activity is a good opportunity to teach students how to indicate scale on diagrams
and to explain the way in which it is indicated in the materials. Students should be shown
specimens of some of the plants indicated on the sheets so that they can compare their
sizes with the diagrams. They should be encouraged to relate this to the indication of size.
ScO
4 a use a wide range of scientific and technical vocabulary and conventions, and to use
diagrams, graphs, tables and charts to communicate information and to develop an argument
Other resources
NCS Biology Chapters B13 and B16.
Pathways Sourcebook Environment pages 24-25 gives information about studying
habitats.
Nuffield Science Calculations, Topic 39 (Sampling plants) explains the quantitative
method.

B88 Red squirrels (H)
B14 The impact of human activities 125
REQUIREMENTS
Students will need:
activity sheet
Notes on the activity
The main content of the worksheet is based on R. E. Kenward's work on the British red
squirrel, described in Biological Journal of the Linnean Society, 1989, 38, pages 83-90.
There is an opportunity here to discuss other introduced species and their effect on the
'balance of nature' in the area where they are introduced, e.g. the New Zealand flatworm,
now found in Britain and a serious predator of earthworms. Both the flatworms and
earthworms are eaten by beetle larvae, so a new balance will develop. As the number of
earthworms decreases, there will be more chance of the beetle larvae eating flatworms,
rather than earthworms. So the earthworm population will recover.
Answers to questions
1 The two squirrels may compete for food for much of the year (e.g. tree bark and fungi
in January, buds and shoots in May). In autumn, grey squirrels eat more acorns, red
squirrels eat more hazelnuts if both are plentiful. However, the grey squirrel is more
adaptable and can eat hazelnuts if necessary.
2 Both squirrels build dreys of twigs among the branches of trees. Grey squirrels may
take over a rook's nest. Red squirrels may make a den in an old, enlarged woodpecker's
nest. It is unlikely that the number of squirrels is limited by suitable sites for a drey.
3 There has been a decline in the number of hazel trees.
4 Students could approach this in the same way as a Scl investigation, making sure
that it is a fair test. They might, for example, suggest choosing two areas of the woodland
which are similar in all other respects (a chance to discuss the problems of fair testing in
environmental work!). One could be planted with a high density of oak trees, the other
with the same density of hazel. Equal numbers of red and grey squirrels could be introduced
into each area, and the population sizes recorded for the next few years.
There is an opportunity to mention the food trap used in Thetford Forest. This is
weighted to favour the red squirrel, as red squirrels weigh 350 g and grey squirrels 700 g.
food reservoir
45cm
15cm
Stop on roof
prevents trapdoor
swinging past the
vertical
Cou iterweight.
Adjustable magnet
holds trapdoor up -
strong enough to
support weight of red
squirrel.
Trapdoor falls open under
greater weight of grey,
preventing it from reaching
the food, while red can
cross the trap safely.
Wire mesh stops grey pushing
trapdoor up from below.

126 B14 The impact of human activities
Other resources
Nuffield Science Calculations, Topic 37 (Sampling animals) gives examples of capturemark-recapture
for estimating the size of a population.
B89 Types of pollution
REQUIREMENTS
Students will need:
activity sheet
textbooks
Notes on the activity
This activity could be the basis for discussion in class or set as a homework. Students
may want to cut out the diagram, label it more fully, perhaps colour it and add it to their
notes.
This activity will give you a good idea of the level of general knowledge about
pollution among students in your class. Many will be confused and unable to distinguish
the causes and effects of problems such as the greenhouse effect and the 'hole' in the ozone
layer, acid rain and other forms of air pollution. This is an opportunity to clarify some of
these issues.
Answers to questions
Type of
pollution (air,
water, living
things)
Air
Air
Air
Where the
pollution
comes from
Coal and oil-fired
power stations,
motor vehicles,
industry
Burning coal, oil,
natural gas and
wood
Leaks from
refrigerators and
air conditioning
plants. Also from
foam insulation
The main
pollutant(s)
Sulphur dioxide
and nitrogen
oxides which
form acid deposits
on buildings and
acid rain
Carbon dioxide
Chlorofluorocarbons,
(CFCs)
The damage
done by the
pollutant
Limestone
buildings decay
and metals
corrode. Acid
water in rivers
and lakes kills
fish and other
living things
Adds to global
warming by the
greenhouse effect
Destroys ozone in
the stratosphere
creating thinner
regions (or
'holes' in the
ozone layer)
How to stop
the pollution
Burn low-sulphur
fuels. Remove
sulphur dioxide
from power
station fumes.
Redesign engines
and boilers to
form less
nitrogen oxides
Save energy
resources by
insulating homes,
using more
efficient lighting
and machinery,
cutting out
unnecessary travel
Replace CFCs
with alternative
chemicals

B14 The impact of human activities 127
Water
Water
Water
Water and living
things
Sewage outfalls,
wastes from
intensive animal
farming
Land ploughed
and fertilized to
grow crops
Cooling towers
in power stations
and industrial
plants
Horticulture and
agriculture
Organic matter
Nitrates
Warmer water
Persistent
pesticides
Oxygen levels
fall rapidly as
bacteria
decompose
organic matter.
Fish and other
living things die
Fertilizes algae in
rivers and lakes
(eutrophication).
When the algae
die and rot,
oxygen levels in
the water fall
rapidly so that
fish die
Lowers the
solubility of
oxygen. Speeds
the metabolism
of animals and
plants. So
animals need
more oxygen but
there is less
available
Disrupt food
chains and webs.
Kill natural
predators.
Accumulate in
food chains
Treat all sewage
before pouring it
into rivers or the
sea. Improve farm
systems for
handling, storing
and disposing of
animal wastes
Seed new crops
soon after
ploughing. Limit
the use of
fertilizers
Operate combined
heat and power
systems with
hotter cooling
water used for
heating homes,
offices and
factories
Use selective
pesticides which
rapidly break
down in the
environment. Use
biological control
Opportunities for co-ordination
P97 'What happens in a power station?' considers the treatment of waste gases in a power
station.
ScO
2 c relate scientific knowledge and understanding to the care of living things and of the
environment
Other resources
Pathways Sourcebook Environment pages 4, 14-15, 16-17, 32-33, 34-35.
B90 Monitoring water pollution
REQUIREMENTS
Students will need:
activity sheet
indicator animals sheet
net
disposable gloves
plastic tray

128 814 The impact of human activities
Safety note
Refer to the notes at the beginning of this section and on pages 3-5, for advice about
fieldwork. Depending on the water and the pupils, you may feel disposable plastic gloves
are a good idea.
Notes on the activity
You may want to give your students a fuller briefing about sampling techniques and
indicator animals. A video can help. The Animal Ecology booklet of the National
Environment Database project is also helpful.
Discourage students from trying to catch fishes and encourage them to treat all living
things with the respect they deserve. Please note that you could collect water samples for
Activity B91 whilst doing this activity.
A video camera, if available, makes an excellent 'notebook' for this kind of activity.
The tape can be played back during subsequent lessons and used to answer questions such
as 'How did it breathe?', 'How did it move?'. You can also film creatures which students
cannot identify at the time for later study. You might build up a library of the creatures
found in your local stream for showing before the students go out. Such a tape can be
paused, rewound and viewed again - unlike the animal!
If you can persuade a parent or colleague to operate the camera for you it can prove
immensely useful. However, it is a good idea to brief them beforehand so that they
concentrate on getting shots of the animals not snaps of the students.
There are various species of all the creatures shown on the sheets so don't be surprised
if the animals which your students find do not look exactly the same as those shown in
the pictures.
You can link this activity to the work of the National Environment Database project
which will give your students experience of feeding data into a database and down loading
information for analysis. You will need the project's publications and software together
with a suitable computer. (See under Further information - addresses.)
As well as being an exercise in pollution monitoring, this activity also gives students
further opportunities to study ways in which living things are adapted to survive in their
natural habitat. You can lead into this by asking students to consider why some organisms
can only live in unpolluted streams while others survive despite pollution.
Notes on the animals
The indicator animals are usually quite easy to find if the students have a bit of patience.
They are all delicate so students should handle them very carefully. Return them as soon as
possible to the place where they were collected.
Note that the easiest way to tell the difference between mayfly and stonefly nymphs is
to count the number of tails. Mayfly nymphs have three, while stonefly nymphs have
two. Students may not see any stonefly nymphs even in clean water. The caddis fly larva
makes its own little house. If there's apiece of twig walking around the white tray, it's a
caddis fly larva.
Bloodworms and sludge worms are red because they have haemoglobin like humans.
They take in oxygen, by diffusion, over the whole of their bodies. This allows them to
survive in water with lower oxygen concentrations than other similar organisms can cope
with.
Mayfly and stonefly nymphs breathe using external gills. They have no haemoglobin
so the oxygen circulates in their bodies in solution. This means that they need a higher
concentration of oxygen in the water where they live than bloodworms and sludge worms.
In unpolluted water, however, the nymphs are more mobile and compete successfully for
food with the worms.

B14 The impact of human activities 129
Answers to questions
Comparison of streams A and B
Mayfly Caddis fly Freshwater Water Blood Sludge
nymph larva shrimp louse worm worm
b Comparing the bar chart
with the table of indicator
animals suggests that stream A
is only slightly polluted while
stream B suffers high pollution.
The stream B might flow
through a heavily industrialized
area or be fed by the outflow
from a sewage works. Regular
pollution from farming wastes
could also be responsible for the
low oxygen levels, which mean
that bloodworms can live in the
water but not mayfly nymphs or
caddis fly larvae.
(ij| stream A
B stream B
ScO
2 c relate scientific knowledge and understanding to the care of living things and of the
environment
4 a use a wide range of scientific and technical vocabulary and conventions, and to use
diagrams, graphs, tables and charts to communicate information and to develop an
argument
Other resources
NCS Biology Chapter B17.
Pathways Sourcebook Environment pages 32-3 gives information about water
purification.
The Pathways Sourcebook Environment, page 34 has an article on our use of river water,
which is also on the disc.
On disc
Extract from the Pathways Sourcebook Environment, page 34.
B91 Nitrates in water
REQUIREMENTS
Students will need:
activity sheet
nitrate test strips (see note 1)
a range of water samples (see note 2)
Students will find useful but not essential:
a computer and printer
nitrates survey database
Notes:
1 Nitrate test strips are available from Merck Limited. An alternative approach would be
to use the nitrate test kits for aquaria.
2 The activity could involve rain water, pond water, stream water and tap water.
Alternatively, in an agricultural district, it might be interesting to compare streams near a

130 B14 The impact of human activities
dairy farm with those near arable farming. You might decide to make up fictional water
samples using the figures quoted on the sheet as a guide.
Safety note
Emphasize the need for hand washing if water other than tap water is used.
Notes on the activity
There is a Field Studies Council Booklet which supplements the work in this activity
called Nitrate - Environment and Health. This booklet gives details of a number of
possible investigations and explains how the nitrate test strips work.
The KEY datafile on disc includes records of measurements made by the Field Studies
Council over a year. It contains up-to-date statistics and information. Water companies and
the National Rivers Authority can also provide up-to-date information on nitrates in water
supplies.
Here are examples of the hypothesis you can test with KEY and the datafile:
• Are high levels of nitrate in streams due to run-off from arable areas?
• Does the altitude of a sampling site affect the likelihood of finding nitrate in the water
tested?
There are forces at work in the soil tending to remove the nitrogen which the farmer
adds. The crop's intended nutrient is turned into a pollutant of air and waterways.
NH4* can evaporate straight into the atmosphere as ammonia gas (NH3+ ).
Nitrifying bacteria turn the NH4 to nitrate and denitrifying bacteria convert this NCy
to nitrogen and oxides of nitrogen, which also diffuse into the air. These are the most
important reasons for soil loss of nitrogen during summer.
If the soil is too cold for crops to absorb nitrogen - or the crops are harvested and the
soil is bare - surplus NO,- is leached out of the soil by rain, and runs off into the
waterways. It may accumulate in groundwater - and in high concentrations can be
dangerous. It converts to nitrite, NO2-, which in humans can combine with the
haemoglobin in the blood. This inhibits oxygen uptake and in babies may lead to
methaemoglobinaemia or 'blue baby syndrome'. More commonly, excess nitrogen
running into ponds or lakes leads to algal blooms - excess of algae, which die and then
they decay. The bacteria causing this decay rob the waterway of oxygen, so that everything
may die. Run-off of nitrogen occurs mainly in winter.
This run-off can be caused by both excess artificial fertilizer and organic manures
applied at the wrong time: slurry on bare autumn fields is among the worst culprits.
Recent research at the Rothamsted Experimental Station in Hertfordshire has shown that
the main source of run-off in the 1980s was grassland that was ploughed up during World
War II to make way for arable food crops. The nitrogen from the rotting grass has taken
more than 40 years to work its way down to the groundwater.
ScO
2 c relate scientific knowledge and understanding to the care of living things and of the
environment
Other resources
NCS Biology Chapter B17.

B14 The impact of human activities 131
B92 Acid in the air
REQUIREMENTS
Students will need:
activity sheet
plant seedlings in small pots - barley and maize
transparent plastic bags with seals
tongs
cotton wool
textbooks
Access to:
Campden tablets, available from Boots or home-made wine suppliers
sticky labels
tweezers
Note:
It may be best to use plastic bags if the seedlings are to be left in a fume cupboard.
However, watch for low light effects on the seedlings.
Safety
Sulphur dioxide is an irritant which will affect asthmatics.
For this reason, the trays of seedlings should be clearly labelled with a warning, and
dismantled in a fume cupboard or outside in the open air.
Notes on the activity
There is scope within this experiment for students to compare the effect of sulphur dioxide
on a wide range of plants. This is worth doing because susceptibility varies a great deal.
More able students could be encouraged to speculate about the reasons for these differences.
They could then test their theories by experiment.
Here are some of the key points about acid rain which students might mention in their
articles:
• The pH of unpolluted rain is naturally about 5.0 because of dissolved gases such as
carbon dioxide. The pH of acid rain is lower than this - in the range 2 to 5.
• Coal and oil contain sulphur. When these fuels burn the sulphur turns into sulphur
dioxide. Sulphur dioxide reacts in the air and in clouds to form sulphuric acid. Sulphuric
acid makes rain water more acid.
• Some sulphur dioxide enters the air naturally from volcanoes and the decay of dead
plants, but in Europe about 90 per cent of sulphur dioxide in the air comes from industry
and motor vehicles.
• Burning fuels produces oxides of nitrogen because the temperatures get hot enough for
nitrogen from the air to combine with oxygen. Oxides of nitrogen add to acid rain because
they turn into nitric acid in the atmosphere. Motor vehicles produce most of the oxides of
nitrogen but power station boilers also produce a lot.
• Living things in lakes may die if the pH falls below 5. Many thousands of lakes in
Norway and Sweden have little or no life.
• Acid rain speeds up the corrosion of metals.
• Acid gases in the air speed up the decay of stonework, especially limestone.
• Many trees in Europe are dying. Some scientists say that this is due to acid rain.
Other experts disagree and say that the damage is done by drought, disease, pests or other
types of air pollution.
Opportunities for co-ordination
P97 'What happens in a power station?' considers the treatment of waste gases in a power
station.

132 B14 The impact of human activities
ScO
2 c relate scientific knowledge and understanding to the care of living things and of the
environment
Other resources
NCS Biology Chapter B17.
Pathways Sourcebook Environment pages 14-16.
B93 How do pollutants affect Chlorella?
REQUIREMENTS
Students will need:
activity sheet
table lamp
light sensor
glass jar
magnetic stirrer
eye protection
Access to:
Chlorella culture
datalogger and software
a safe place to leave the apparatus overnight
detergent, acid and nitrate solutions (see note)
Note:
The exact details of setting up the experiment and calibrating the sensor will depend on the
equipment used.
For instance, if you use a Philip Harris Sensor with a Philip Harris Universal
Interface, you calibrate for Datadisc using the following procedure.
From the main menu press C to calibrate
Select the channel, e.g. press 1
Press P for Philip Harris Sensor
Press L for the Light Sensor Log range
Press Enter
Switch the sensor to BAIT. Press Spacebar
Switch the sensor to ON. Press Spacebar.
Notes on the activity
This experiment is a good example of the use of datalogging equipment because it
closely models the use of control electronics in biotechnology to monitor fermenters. It
demonstrates the way that dataloggers can be used to monitor experiments over long
periods of time and to plot graphs directly. It is easy to set up and works well.
The activity needs careful classroom management when using a datalogger because
only one group can use the equipment at a time. You might arrange for this activity to run
in parallel with some of the other activities which require less apparatus.
If a datalogger is not available, students can withdraw samples at regular intervals and
take readings using a colorimeter.
Students may need help in interpreting graphs of growth, particularly in relating
gradient to rate of growth.
This would be a good opportunity to compare a range of growth curves, e.g. the
human population over the last 2000 years, populations of a related predator and prey, and
length of a simple insect, such as a locust, to show the 'steps' in the graph, related to
moulting.
The following may be helpful to students in their investigation.

Suppose students are studying the effects of warm water from power-station cooling
towers on wildlife in rivers. If so, they will be investigating the effect of temperature on
the growth of the Chlorella culture. The first thing to decide is the range of temperatures
to use. Water for a power station in summer is taken in at about 18 °C and discharged at
about 27 °C. In winter the range might be 7 °C to 20 °C. So in the investigation they
might try to cover the range from about 5 °C to 30 °C.
The results from the datalogger will be a series of traces, one for each set of
conditions. The steeper the graph, the faster the rate of growth of the culture. To turn this
'steepness' into a number draw, a tangent to the curve, then find the gradient.
The bigger the gradient, the faster the rate of growth of the culture. Students could
plot a graph of these rates of growth against the variable they are investigating to give you
a better picture of the pattern of the relationship between the variables.:
ScO
Id judge when to use IT to collect, handle and investigate scientific information
2 c relate scientific knowledge and understanding to the care of living things and of the
environment
B94 Global warming
REQUIREMENTS
Students will need:
activity sheet
Access to:
library books
Notes on the discussion
B14 The impact of human activities 133
Actions which might
help to cut down on
greenhouse gases
• cycling to work
• investing in nuclear power
• installing a gas boiler
• supporting social and
economic development in the
developing world
• recycling aluminium (if it
leads to more sustainable
technologies)
• fitting loft installation and
using more efficient light bulbs
• planting a tree
• stopping smoking (much
wood is burnt to cure tobacco)
Actions which have little
or no effect
• buying chairs made of wood
• putting rubbish on a compost
heap (makes no difference - the
rubbish rots more slowly but
gives off nearly as much carbon
dioxide in the end)
• not mowing the lawn
Actions which might do
more harm than good
• getting rid of a deep freeze (if
scrapped without recovering
CFCs)
• fitting a catalytic converter (if
it makes the engine less
efficient)
• installing a gas boiler
• supporting social and
economic development in the
developing world (if it leads to
rapid economic growth on a
Western model)
Opportunities for coordination
Chemistry Activity C14 also considers global warming.
ScO
2 c relate scientific knowledge and understanding to the care of living things and of the
environment

134 B14 The impact of human activities
Other resources
Pathways Energy resources Sourcebook pages 18-19.
SATIS 1206 The greenhouse effect. Association for Science Education (1991)
B95 In defence of modern farming (H)
REQUIREMENTS
Students will need:
activity sheet
They may also need access to:
recent newspaper and magazine articles
audio or video tape recorder
Notes on the activity
This activity provides students with two views of modern farming methods. They
summarize the opposing points of view.
There is an opportunity to make this activity topical. Most water companies publish
news sheets or bulletins which may contain details of recent incidents and the prosecution
of farmers. Students could be invited to collect similar items from newspapers and
magazines for homework. "Which? is a good source of up-to-date information on the
consumer issues connected with this topic. You could also make use of environmental
series on the TV such as Country File. Students could find out the cost of free-range and
battery eggs (of the same size) from the supermarket, and the cost (per kg) of free-range and
battery-reared chickens.
Another approach to the activity is to develop the pesticides theme. There is a relevant
ICI video presented by David Bellamy called Safety side up. The British Agrochemicals
Association have produced a series of leaflets about pesticide use. To spray or not to spray
is a resource pack produced by Hobsons working with the British Crop Protection Council
and the Association of Agriculture. Pesticides in farming can also be approached through
computer software.
Nitrates in water is a discussion pack produced by the Association of Agriculture. It
includes genuine responses from environmental and farming organizations to an enquiry
from an imaginary MP.
Opportunities for co-ordination
C67 considers the benefits and costs of producing fertilizers.
ScO
1 b use and bring together information from a range of secondary sources
2 a consider ways in which science is applied and used, and to evaluate the benefits and
drawbacks of scientific and technological developments for individuals, communities and
environments
Other resources
NCS Biology Chapter B15, B17.
Pathways Sourcebook Environment pages 12-13 (organic farming) and pages 36-7
(biological control).
On disc
The two articles mentioned under Other resources are available on the disc.

B14 The impact of human activities 135
Answers to questions
When students study the two farming methods they may produce the following
comparisons. They may also wish to add other aspects of farming, such as monoculture,
loss of hedgerows and erosion.
Varieties of
crops
Sources of
nutrients
Animals reared
Methods of
looking after
animals
Dealing with
pests and
diseases
Treatment of
wastes
Quality of the
produce
Impact on
wildlife
Intensive farming
Monoculture — the same crop grown year
after year. Short stemmed varieties to give
as much yield as possible in the grain
Chemical fertilizers
Limited range of animals in large numbers
- maybe kept indoors much of the year
Chickens in battery cages. Regular use of
drugs to prevent disease in animals.
Hormones used to control or promote
growth
Crops sprayed routinely with herbicides,
fungicides and insecticides
Straw burnt. Animal wastes stored in slurry
tanks. Slurry used to fertilize grassland. A
danger having too much slurry to dispose of
Reliable product of consistent quality. May
have traces of pesticides
Pesticides greatly reduce the variety of
insect life. Larger, hedge-free fields provide
fewer habitats for wildlife
Organic farming
Crop rotation including plants with
nitrogen-fixing root nodules. Tall varieties
chosen to shade out weeds
Manures, compost and minerals
Smaller numbers with greater variety of
animals. Balance between arable and
livestock farming
Free range chickens. Drugs avoided except
when animals are ill. Poorer conversion of
food to flesh when temperature is lower
Pesticides not used. Biological control of
pests where possible. Weeds controlled by
harrowing and by growing tall varieties.
Weeds ploughed in to enrich the soil at the
end of the year
Straw ploughed back into the soil or used
as bedding for animals. Animal wastes used
as manures to fertilize crops
Appearance and quality may be more
variable. Pesticide free. Flavour and
nutritional value a matter of opinion
Ploughing and manuring can cause as
much, or more, nitrate run off than using
chemical fertilizers. Smaller fields with
hedges to provide homes for predators
which control pests
B96 Plant protection in Thailand (H)
REQUIREMENTS
Students will need:
activity sheet
sample of okra would be useful
Notes on the activity
As well as being the basis of a worthwhile data analysis exercise, this activity also shows
that scientific research is now of worldwide importance.

136 B14 The impact of human activities
Answers to questions
1 Here are two graphs displaying selected data.
8 16 24 32 40 48 56 64 72 80 88 96
Days from start of experiment
8 16 24 32 40 48 56 64 72 80 88 96 104
Days from start of experiment
eggs-insecticide
x————x virus treated
insecticide treated
larvae - insecticide
*-__-_-x eggs-virus
+—————f
larvae-virus
2 The numbers of larvae start to fall on the virus plot soon after spraying starts. The
number of eggs continues to rise in much the same way on both plots suggesting that
adults are not affected by the virus and go on laying eggs. If the virus affected the eggs one
might expect a delay until infected eggs fail to hatch while existing larvae survive.
The infected larvae die before they become egg-laying adults so after a time the
infection of larvae leads to a fall in the number of eggs.
3 On day 34 on the insecticide plot there is a peak in the number of larvae and a peak in
the number of damaged pods. There are smaller peaks in the numbers of larvae and damaged
pods on day 55 too. It looks very much as if the larvae damage the pods.
The pattern is similar on the virus plot where the much lower peaks in the numbers of
larvae more or less match the rise and fall in the numbers of damaged pods.
4 The numbers of larvae, damaged flowers and damaged pods were much less on the virus
plot than on the insecticide plot. In this trial the virus was clearly effective. The scientists
had more to do, however, before they could recommend lots of farmers to spray with the
virus. They needed to do more experiments to check the longer terms effect of spraying. The
bollworm was becoming resistant to pesticide; could it similarly gain resistance to the
virus? Are other living things affected by the virus?
Since the virus infects the larvae, the time to spray is a few days after the farmers sees
the eggs. By then the eggs have hatched and the virus infects and kills off the emerging
larvae before they can do much damage.
5 Pesticides are toxic chemicals and high doses may affect plant growth. With higher
doses it is more likely that traces of the pesticide will remain in the harvested crop.
Customers are increasingly worried about pesticide residues, and importers in Japan and

Europe will not buy crops if pesticide levels are too high. This cuts the value of the
farmer's crop.
6 There is not enough information to decide whether or not biological control is
worthwhile. Spraying with the virus is more expensive but at the time of the trial it was
much more effective than the insecticides. The extra cost would be worthwhile if it
increased the quantity and quality of the crop to justify the expense.
ScO
4 a use a wide range of scientific and technical vocabulary and conventions, and to use
diagrams, graphs, tables and charts to communicate information and to develop an
argument
Other resources
Pathways Sourcebook Environment pages 36-7 gives information about biological control.
B14 The impact of human activities 137_

Nuffield Biology
Further information and addresses
Further information about plant nutrition
Booklets posters and other sources of information
Bell B and Brook A (1984) Aspects of Students Understanding of Plant Nutrition: full
report, Childrens Learning in Science Project, Centre for Studies in Science and Maths
Education, University of Leeds.
Bell B, Barren J and Stephenson E (1985) The construction of meaning and conceptual
change in classroom settings: case studies in plant nutrition, Childrens Learning in
Science Project, Centre for Studies in Science and Maths Education, University of Leeds.
Science and Plants for Schools (SAPS) publish a series of leaflets and newsletters
describing the results of their continuing programme to develop new techniques and ideas
for the study of plants in schools.
Science for survival by Adam Cade (1988), published by WWF, provides some interesting
information and activities involving plants, with an emphasis on rain forests.
Further information about food and digestion
Booklets, posters and other sources of information
Local health authorities and superstores offer a wide range of free useful leaflets.
Davies, J. and Dickerson, J. 1991 The nutrient content of foods. The Royal Society of
Chemistry
Diet, nutrition and prevention of chronic disease. World Health Organization
Enjoy healthy eating. Health Education Authority
Finding out ... what happens when I drink. Hobsons Scientific 1989
Food for thought. Health Education Council
Marshall J and Heughan A Eat for life diet. Vermillion
SATIS Units 104 What's in our food?, 108 Fibre in your diet, 302 Living with kidney
failure, and 703 Vegetarianism might be used to complement this topic. The SATIS 14-
16 series is published by the Association for Science Education. See also Update 91 with
its suggestions for updating and improving the units.
Sources of equipment and materials
The digestive system (Bioset Ml7). Banta
Human X-ray print set from Philip Harris, showing the progress of food along the
intestine.
Further information about human physiology
Booklets, posters and other sources of information
Body can you spare a part? TVS Education
Clinistix (used to detect glucose in urine) and Albustix (used to detect protein in urine) can
be obtained from a local pharmacy or from Ames Division, Bayer Diagnostics Ltd.
Finding out... what happens when I breathe. Hobsons Scientific 1987
Finding out... about medical research, Hobsons Scientific 1988 has a section on heart
disease.
'Heart information' series from the British Heart Foundation
Making a new start and Beating heart disease. Health Education Authority

Further information 139
SATIS units 603 The heart pacemaker, 802 Hypothermia might be used. The SATIS 14-
16 series is published by the Association for Science Education. See also Update 91 with
its suggestions for updating and improving the units. A radio programme in the SATIS 14-
18 series to accompany Unit 603 available on tape from the ASE.
Twice blessed. National Federation of Kidney Patient Associations
The UK Transplant Co-ordinators' Association (see 'Addresses') distributes short, clear
leaflets for doctors, nurses and other health professionals. These may be available from your
local transplant co-ordinator. There is a list of addresses for transplant co-ordinators in Unit
7 Kidney transplants of SATIS 16-19 from the ASE.
Computer animation and videos
Graphics of the working heart and lung are included with the software for LogIT (see
below).
Graphic hearts program, Griffin and George, YTH-150-A shows half-heart and whole heart.
The names and technical details are pitched at quite a high level.
'The body machine', Science in Action
'Blood and circulation in the living body', Focal Point Audiovisual
Sources of equipment and materials: data logging equipment
LogIT from Griffin and George is compatible with BBC B/Master, Archimedes, RM
Nimbus and IBM computers. The heart and breathing monitor program gives complete
coverage of the ideas contained in this topic.
The heart monitor and the breathing monitor (which measures breathing rate and tidal
volume) can be used simultaneously. Graphics of the working heart and lung are included,
the latter being particularly good. The heart monitor straps round the chest next to the skin.
Good contact can be achieved using KY gel. The heart sensor can be used remotely and the
results fed into the computer later.
Fitness analysis software (YTH-146-R) is available for LogIT and includes calculation of
fitness index for controlled activity. It is suitable for use at several levels of difficulty and
comprehensively covers aerobic and anaerobic activity. The breathing monitor is not remote
but has a lead long enough to allow press-ups or cycling on an exercise bicycle. Breathing
rate and tidal volume can be monitored simultaneously and displayed.
Educational Electronics supply 'Sense and control' with a pulse monitor and software for
the BBC Master. The software includes real time plots of pulse and pulse rates, calculation
of fitness index, and a beating heart simulation which can be synchronized with the
student's pulse. Student worksheets and a comprehensive teachers' guide are available.
Slides and photographs of tissues
Prepared microscope slides from Philip Harris or Griffin and George
The breathing organs of the body (Bioset M21), Banta
The circulatory system (Bioset M22), Banta
Human blood (Bioset M6), Banta
Further information about the carbon and nitrogen cycles
Booklets, posters and other sources of information
The Alternative Technolgy Centre at Machynlleth, the Henry Doubleday Research
Association and the Soil Association all publish leaflets on composting technology.
SATIS units 201 'Energy from biomass', 803 'The Technology of Toilets', 1206 'The
greenhouse effect' might be used to complement this topic. The SATIS 14-16 series is
published by the Association for Science Education. See also 'Update 91' with its
suggestions for updating and improving the units.
Wallcharts and booklets from Shell covering biological cycles.

140 Further information
Further information about health
Booklets, posters and other sources of information
Information about vaccination before holidays abroad from British Airways Travel Clinics
and from the Medical Advisory Service for Travellers abroad.
ABPI 1991 Medicines, health and you. Poster set with booklet of activities sent free to all
UK schools and colleges in 1991. Further copies are available from the ABPI.
AIDS - working with young people, a teaching pack from AVERT
AIDS and young people, a simple but explicit booklet from AVERT
Thomas G ADDS and you game. Cambridge Resources Packs
Leaflets about AIDS from Scriptographic publications Ltd.
Morgan D (ed) 1991 Aids andyou, an illustrated guide to HIV and AIDS 2nd edn. BMA and
the Health Education Council
Drug misuse: a basic briefing and other leaflets from the Health Publications Unit.
Finding out about... medicines and drugs. Hobsons Scientific 1990
Finding out about... drinking and driving. Hobsons Scientific 1989
Finding out about... smoking. Hobsons Scientific 1989
SATIS Units 203 Drinking alcohol, 606 The Tristan da Cunha dental surveys, 609
Hitting the target - with monoclonal antibodies, 805 The search for the magic bullet, and
909 AIDS might be used to complement this topic. The SATIS 14-16 series is published
by the Association for Science Education. See also Update 91 with its suggestions for
updating and improving the units. Also relevant is activity 7.7 'Tooth decay in England in
Wales' in the SATIS Atlas.
So you want to stop smoking and other leaflets from the Health Education Authority
Sensible drinking, No 5 in Sainsbury's 'Living Today' series deals with alcohol
Slides
Smoking and health (Bioset M73), Banta compares healthy and diseased lung tissues.
Further information about cancer
Booklets posters and other sources of information
Cells, cancers and communities, by A. Charlton, Stanley Thornes (pupils' resource book
and teachers' book), 1988
Talking about cancer, by B. Johnson and S. Lennon, Marie Curie Memorial Foundation,
28 Belgrave Square, London SW1X 8QC (a multimedia pack)
Can you avoid cancer? Health Education Council booklet
Booklets and leaflets from the Cancer Research Campaign and the Imperial Cancer Research
Fund.
Videos
Can you avoid cancer? BBC video series from BBC Enterprises. Each video is about 25
minutes long. Video 1 covers basic facts
Further information about nerves and hormones
Booklets posters and other sources of information
Leaflets and booklets from the British Diabetic Association.
Slides
Microslides of body cells are available from biological suppliers.

Further information 141
Further information about reproduction
Booklets posters and other sources of information
'Build a flower' from J C Torrance's Biological games and puzzles is a useful model using
cutouts of individual structures to build up an entire flower.
The Health Education Authority and the Family Planning Association publish a range of
information leaflets and booklets. The lists change often, so it is best to write for a current
catalogue.
SATIS 206 'Test tube babies' contains information and discussion questions on the
problems of infertility and the technique of in-vitro fertilization.
Science and Plants for Schools (SAPS) are continually testing new techniques and ideas for
the use of plants in schools.
Videos and slides
The BANTA Bioset M29 Reproduction in mammals has 8 slides showing the development
of an embryo (for use with a bioviewer).
The BANTA Bioset B27 is about the structure of a flower (for use with a bioviewer).
A relevant set of 10 microscope slides on angiosperm reproduction is available from Philip
Harris.
Focal Point Audiovisual has a set of 30 colour slides on reproduction in flowering plants.
'Growing Up' from the Health Education Authority is a useful video about puberty.
Further information about inheritance
Zoos, botanical gardens and museums are good sources of information on variation in
species. A local museum may have a collection of specimens which is adequate for this
course. Some museums and local authorities will loan specimens to schools. Others offer
staff to give talks about a collection or to visit the school with a few specimens.
The Natural History Museum produces a good range of educational materials and booklets
relevant to this topic.
Booklets, posters and other sources of information
Biotechnology and you: some examples of the impact of biotechnology on society,
Biotechnology with Schools Project, from the Agriculture and Food Research Council
Borin van Loon DNA: the marvellous molecule. Tarquin Publications, 1990. ISBN 0
906212 75 8. A booklet with colourful cutout models of the double helix, nucleotides and
viruses.
Butterflies: a practical guide to their study in the school grounds via the National
Curriculum by J. Feltwell. Learning through Landscapes Trust, 1990.
ISBN 1 872865 00 3.
Publications from the Cystic Fibrosis Research Trust
Genetics and the individual. Warwick Process Science.
Gonick and Wheelis. The cartoon guide to genetics. Barnes & Noble Books, 1983.
ISBN 006 4604160.
Plant tissue culture, by Tony Storr, No. 13 in Experimenting with Industry series,
Association for Science Education, 1985.
Practical Biotechnology: a guide for schools and colleges, National Centre for
Biotechnology, 1993.
Rosenfield, Ziffk and van Loon. DNA for beginners: a writers' and readers' documentary
comic book. ISBN 0 86316 023 0.
Newsletters and booklets from Science and Plants for Schools (SAPS).
SATIS 14-16 series is published by the Association for Science Education. SATIS unit
309 Microbes make Human Insulin, 710 What is Biotechnology?, and 1204 From
Babylon to Biotechnology . See also Update 91 with its suggestions for updating and
improving the units.

142 Further information
Videos, slides, TV programmes and computer animation
An introduction to practical microbiology, Manchester Metropolitan University, available
with a 35-page booklet.
RSPB Videoguide to British birds.
A Ilium root tip squash and Crocus balansae root tip squash, from Philip Harris.
BANTA Bioset B4 is about plant mitosis (for use with a Bioviewer).
Sources of equipment and materials
Murashige and Skoog medium and kinetin are available from school suppliers such as
Philip Harris.
Philip Harris markets the practical genetics kits developed in association with SAPS.
Tomato seeds from Philip Harris.
'The gene kit' from Philip Harris provides beads and so on for building a DNA model.
The human chromosome analysis set' from Philip Harris allows students to examine
karyotypes.
The genetics risk game' and 'Genetics cards' from Philip Harris
Further information about evolution
Booklets, posters and other sources of information
Man's place in evolution, British Museum (Natural History), 1980.
Origin of species, British Museum (Natural History )/Cambridge University Press, 1981.
Hammond, J., Bowman, J.C. and Robinson, T.J. Hammond''s farm animals. Edward
Arnold. ISBN 07131 28488.
Johnson, M. Flying dinosaurs. Penguin, 1990. ISBN 0 14 011270 7. Ten flying dinosaur
gliders to make.
'Learning from fossils'. Poster from Shell Education Service.
Evolution and diversity. Warwick Process Science.
A local museum, zoo, or botanical gardens might be a good source of information.
The Natural History Museum produces educational material and booklets about various
aspects of evolution.
Videos, slides, TV programmes and computer animation
The evidence for evolution. BBC Biovideo 3 from Focal Point Audiovisual.
Life on Earth, The living planet, and The trials of life from the BBC contain a treasure
trove of useful materials for this episode.
Mechanism of change: Darwin's theory of evolution, from the BBC Biology Collection.
Philip Harris produce a set of OHP transparencies on evolution providing examples of
evidence supporting the theory of evolution.
Sources of equipment and materials
Gamma-irradiated seeds from Philip Harris.
Further information about ecology
Booklets, posters and other sources of information
SATIS unit 906 'IT in Greenhouses' might be used to complement this topic. The SATIS
14-16 series is published by the Association for Science Education. See also 'Update 91'
with its suggestions for updating and improving the units.
Croft, P S A key to major groups of British freshwater invertebrates, Field Studies
Council AIDGAP guide.
Gardening shops and garden centres will have leaflets about the control of garden pests
including aphids. Students can contrast the advice from chemical companies and from

Further information 143
'green' organizations. See for example Garden pests control without pesticides by Mike
Rhodes and Alan Frost from Agralan.
The following environmental organizations publish leaflets, booklets and other educational
resources related to related to this topic:
Friends of the Earth, Royal Society for the Protection of Birds, Ark, The Nature
Conservancy Council, The Wildfowl and Wetlands Trust, Learning through Landscape,
Council for Environmental Education, The Watch Trust for Environmental Education, The
Marine Conservation Society, Department of the Environment, Environmental Protection.
Videos, slides and TV programmes
More and more people is one of the SATIS audio-visual programmes from ASE about
human population growth.
Only one Earth from AVP is a set of nine film strips and optional cassettes which present
the fundamental principles of ecology and our impact on the environment.
Food chains - the balance threatened is a useful slide set with notes for teachers from the
Slide Centre.
Sources of equipment and materials
The Pond Dipping Game' from the World Wide Fund for Nature can be used before or after
pond ecology fieldwork. The handbook with the game suggests practical investigations.
Further information about pollution
Booklets, posters and other sources of information
Acid from the air is a SATIS tape-slide programme from the ASE.
Animal ecology from the National Environment Data Base Project
Nitrate - environment and health by Helen Springall, David Job, Edward Jackson and Sue
Townsend from the Field Studies Council (1991).
Pollution facts (1988) and Conservation facts (1989) by Simon Albrecht from Cambridge
Resource Packs.
Sixth sense from the RSPB.
Features on topical issues in the regular science and environment columns in national and
local newspapers and magazines including New scientist and Farmers' weekly.
Friends of the Earth produce regularly updated information on many environmental issues,
Shell Education News is a useful source of information and resources and ICI produce
various environmental resources including their regular newsletter for schools, STEAM.
SATIS units 210 The pesticide problem', 301 'Air pollution - where does it come from?',
801 The water pollution mystery', 902 'Acid rain' and 1201 'Agrochemicals and the
environment' might be used to complement this topic. The SATIS 14-16 series is
published by the Association for Science Education. See also Update 91 with its
suggestions for updating and improving the units.
Which? magazine regularly includes articles about environmental issues and some
newspapers such as the Guardian publish environmental supplements on a regular basis.
Your local library can give you the address of your county naturalists' trust, a good source
of local information. Many local authorities have published environmental policies which
are worth looking at. Written environmental impact statements which can be viewed at a
local library are produced for any large developments. Your county reference library can
provide information on old maps, records and census returns.
The Association of Agriculture and the Ministry of Agriculture, Fisheries, and Food
publish books and leaflets on agriculture and related topics.
Sources of equipment and materials
Merckoquant nitrate test strips from Merck Limited
Oxygen sensors and data logging equipment are available from Griffin and George and
Philip Harris

144 Further information
Oxygen test kits are available in suppliers' catalogues. They vary in form and mode of use.
They all involve a colour change which is checked against a colour chart. Further
information on oxygen and other sensors used in this module can be found in 'IT in
Science Blue Book; A science teacher's guide to using computers for experiments'
published by the North London Science Centre, 62-66 Highbury Grove, London N5 2AD.
Addresses
Booklets, posters and other sources of information
ABPI (Association of the British Pharmaceutical Industry), 12 Whitehall, London SW1A
2DY (Write to the Science Education Co-ordinator.)
Agralan, The Old Brickyard, Ashton Keynes, Swindon, Wilts SN6 6QR
Agriculture and Food Research Council, Polaris House, North Star Avenue, Swindon SN2
1UH
Animals in Medicines Research Information Centre, 12 Whitehall, London SW1A 2DY
Ark, PO Box 1784, London W9 3QW
Association of Agriculture, 16 - 20 Strutton Ground, London SW1P 2HP
Association for Science Education, Bookselling Department, College Lane, Hatfield Herts
A1109AA
Biomedical Research Education Trust, 58 Great Marlborough Street, London W1V 1DD
AVERT, PO Box 91, Horsham, West Sussex RH 13 7YR
Biomedical Research Education Trust, 58 Great Marlborough Street, London W1V 1DD
British Diabetic Association, 10 Queen Anne Street, London, W1M OBD
British Heart Foundation, 14 Fitzhardinge Street, London W1H 4DH
British Kidney Patient Association, Bordon, Hampshire GU35 9JZ
British Medical Association, Board of Science and Education, Tavistock Square, London
WC1H 9JP
The British Organ Donor Society (BODY), Balsham, Cambridge CB1 6DL
British Union for the Abolition of Vivisection, 16a Crane Grove, London N7 8LB
Cancer Research Campaign, Cambridge House, 6 Cambridge Terrace, London NW1 4JL
Cambridge Resource Packs, 38 Cambridge Place, Cambridge CB2 INS
CLISP, Children's Learning in Science Project, Centre for Studies in Science and
Mathematics Education, University of Leeds, Leeds, LS2 9JT
Council for Environmental Education, School of Education, University of Reading, London
Road, Reading RG1 5AQ
Cystic Fibrosis Research Trust, Department PD 130, Alexandra House, 5 Blyth Road,
Bromley, Kent BR1 3RS
Department of the Environment, Environment Protection, Room A302, Romny House, 43
Marsham Street, London SW1P 3PY
DES Administrative Memoranda may be obtained from Department for Education,
Publications Centre, PO Box 2193, London E15 2EV
English Nature, Northminster House, Northminster Road, Peterborough PE1 1UA
Family Planning Association, 27 Mortimer Street, WIN 7RJ
Field Studies Council, Montford Bridge, Shrewsbury SY4 1HW
Friends of the Earth, 26-28 Underwood Street, London Nl 7JQ
Fund for the Replacement of Animals in Medical Research (FRAME), Eastgate House, 34
Stoney Street, Nottingham NG1 1MB
Greenpeace, Canonbury Villas, London Nl 2PN
Health Publications Unit, No 2 Site, Haywood Stores, Manchester Road, Haywood, Lanes
OL102PZ
Health Education Authority, Hamilton House, Mapleton Place, London WC1H 9TX
The Henry Doubleday Research Association, National Centre for Organic Gardening,
Ryton-on-Dunsmore, Coventry, Warwickshire,CV8 3LG
Hobsons Scientific, Hobsons Publishing pic, Bateman Street, Cambridge, CB2 1BR
ICI Education, PO Box 50, Wetherby, West Yorkshire LS23 7EZ

Further information 145
Imperial Cancer Research Fund, 44 Lincoln's Inn Fields, London WC2A 3PF
Institute of Biology, 20 Queensberry Place, London SW7 2DX
Learning through Landscapes Trust, 3rd Floor, Technology House, Victoria Road,
Winchester, Hants SO23 7DU
Medical Advisory Service for Travellers Abroad, Keppel Street, London WC1
Multiple Sclerosis Society, 25 Effie Road, London, SW6 1EE
National Anti-vivisection Society, 261 Goldhawk Road, London W12 8EU
National Centre for Alternative Technology, Llwyngern Quarry, Machynlleth, Powys
SY20 9AZ
National Centre for Biotechnology , Department of Microbiology, University of Reading,
Reading, RG6 2AJ
National Council for Educational Technology, Sir William Lyons Road, University of
Warwick Science Park, Coventry CV4 7EZ
National Environment Data Base Project, Centre for Educational Studies, King's College,
Cornwall House, London SE1 8TX
The National Fruit Collection at Brogdale, Brogdale Horticultural Trust, Brogdale Road,
Faversham, Kent ME13 8XZ
RSPCA, Education Department, Causeway, Horsham, West Sussex RH12 1HG
Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL
SAPS (Science and Plants for Schools), Homerton College, Hills Road, Cambridge, CB2
2PH
Scriptographic Publications Ltd, Channing House, Butts Road, Alton, Hampshire GU34
1ND
Shell Education Services, PO Box 46, Newbury, Berkshire RG13 2YX
The Soil Association, 86 Colston Street, Bristol BS1 5DD
Tarquin Publications, Stradbroke, Diss, Norfolk IP21 5JP
UK Transplant Co-ordinators' Association, Royal Victoria Infirmary, Queen Victoria Road,
Newcastle-upon-TyneNEl 4LP
The Watch Trust for Environmental Education, The Green, Witham Park, Waterside South,
Lincoln LN5 7JR
The Wildfowl and Wetlands Trust, Slimbridge, Gloucestershire GL2 7BT
The Worldwide Fund for Nature, Panda House, Weyside Park, Godalming, Surrey GU7
1XR
Videos, slides and TV programmes
Animals in Medicines Research Information Centre, 12 Whitehall, London SW1A 2DY
Association for Science Education , Bookselling Department, College Lane, Hatfield, Herts
A1109AA
BANTA Ltd 20, Ridgewood Industrial Park, Uckfield, East Sussex TN22 5SX
BBC Education Information, White City, London W12 7TS
BBC Enterprises, Woodlands, Wood Lane, London W12 OTT
BBC Educational Publishing, PO Box 234 Wetherby, West Yorkshire LS23 7EU.
Boulton-Hawker Films Ltd, Hadleigh, Nr Ipswich, Suffolk IP7 5BG
Curriculum Video Ltd, Freepost, 6C Aberystwyth Science Park, Aberystwyth, Dyfed SY23
3BR
Focal Point Audiovisual Ltd, 251 Copnor Road, Portsmouth, Hants PO3 6EE
John Eastwood Water Protection Trust, Park Hall Trading Estate, London SE21 8EL
Manchester Metropolitan University, Faculty of Science and Engineering, Faculty
Development Unit, John Dalton Building, Chester Street, Manchester Ml 5GD
Mercury Educational Products, 8-10 Lower St James Street, London W1R 3PL
National Federation of Kidney Patient Associations, Stanley Street, Worksop, Notts S81
7HX
Philip Harris Education (for videos, slides and film strips), Lynn Lane, Shenstone,
Lichfield, Staffordshire WS14 OEE
Viscom Ltd, Park Hall Road Trading Estate, London SE21 8EL
World Wide Fund for Nature, Education Department, Panda House, Weyside Park,
Godalming, Surrey GU7 1XR

146 Further information
Sources of equipment and materials
Ames Division, Bayer Diagnostics Ltd, Stoke Poges, Slough SL2 4LY
BANTA Ltd, 20, Ridgewood Industrial Park, Uckfield, East Sussex TN22 5SX
Educational Electronics Ltd, Woburn Lodge, Linslade, Leighton Buzzard, Beds LU7 7UX
Griffin & George (Fisons Scientific Equipment), Bishop Meadow Road, Loughborough,
Leicestershire LEI 1 ORTG
Philip Harris Education, Lynn Lane, Shenstone, Lichfield, Staffordshire WS14 OEE
Merck Limited, Merck House, Poole, Dorset BH15 1TD
Computer software
Angelsoft Educational, 25 Heol Nant, Swiss Valley, Llanelli, Dyfed SAM SEN
Attica Cybernetics, Unit 2, King's Meadow, Ferry Hinksey Road, Oxford OX2 OOP
AVP, Audio Visual Productions, School Hill Centre, Chepstow, Gwent NO6 5PH
Bromley LEA, Town Hall, Tweedy Road, Bromley (for MAPOSE1)
Educational Computing Centre, King's College London, Cornwall House Annex, Waterloo
Road, London SE1 8TX
Garland Computing, 35 Dean Hill, Plymouth PL9 9AF
Hertfordshire IT Advisory Service, Endymion Road, Hatfield, Hertfordshire AL10 8AU
Longman Micro Software, 62 Hallfield Unit, Layerthorpe, York Y03 7XQ
Mercury Educational Products, 8-10 Lower James Street, London W1R 3PL
The Modus Project, The Advisory Unit, Endymion Road, Hatfield AL10 8AU
National Environment Data Base Project, Centre for Educational Studies, King's College,
London SE1 8TX
NCET, Sir William Lyons Road, Science Park, Coventry CV4 7EZ
Philip Harris Education, Lynn Lane, Shenstone, Lichfield, Staffordshire WS14 OEE7
Science Education Software Ltd, Unit 2, Marian Industrial Estate, Dollgellau, Gwynedd
LL40 1UU
Sussex Publications Ltd, Townsend, Poulshot, Devizes, Wiltshire SN10 1SD

BIOLOGY______
ACTIVITIES FOR GCSE
GCSE
courses from
1996
Tsluffield
N12680

NUFFIELD BIOLOGY
ACTIVITIES FOR GCSE
Contents
Section B2 Levels of organization
Bl Skill sheet - Using a microscope (1 side)
B2 Cells and what they do (1 side)
B3 Body systems in Daphnia (1 side)
B4 Body systems in animals (1 side)
Section B3 Nutrition in plants and animals
B5 How do gases get in and out of leaves? (1 side)
B6 Photosynthesis (1 side)
B7 Skill sheet - Testing for starch (1 side)
B8 Plants we eat (1 side)
B9 Do plants and animals alter the environment around
them? (1 side)
B10 What affects the rate of photosynthesis? (1 side)
Bll Factors affecting photosynthesis (1 side)
B12 The food tube (1 side)
B13 The food tube (diagrams to show structure and function)
(1 side)
B14 The food tube (diagrams to show microscopic structure
and digestion of molecules) (1 side)
B15 Enzymes and digestion (1 side)
B16 More about digestive enzymes (2 sides)
B17 The value of villi (1 side)
B18 Foods and food tests (1 side)
Section B4 Transport in plants and animals
B19 Looking at the heart (2 sides)
B20 What does the heart do? (2 sides)
B21 What happens if you have a heart attack? (1 side)
B22 Blood and blood transfusions (1 side)
B23 Looking at diffusion (1 side)
B24 Water in and out of cells (1 side)
B25 Osmosis and turgor (1 side)
B26 Active transport (2 sides)
B27 A summary of mass flow, diffusion, osmosis and active
transport (1 side)
B28 Minerals for plant growth (1 side)
B29 Measuring the rate of water loss from leaves (1 side)
B30 Water from roots through leaves (1 side)
Section B5 Respiration
B31 Where does air go when you breathe in? (2 sides)
B32 How you inflate your lungs (2 sides)
B33 Understanding asthma (1 side)
B34 Investigating respiration (1 side)
B35 How much energy is there in some foods that you eat?
(2 sides)
B36 Investigating cigarette smoke and its effects (1 side)
B37 Smoking (1 side)
Section B6 Energy and nutrient transfer
B38 Energy flows (1 side)
B39 Food chains and food webs (2 sides)
B40 Building pyramids of numbers (1 side)
B41 B uilding pyramids of biomass (1 side)
B42 Pesticides in food chains (1 side)
B43 The carbon cycle (2 sides)
B44 The nitrogen cycle (2 sides)
B45 The nitrogen cycle game (1 side)
Section B7 Health
B46 Body defences (1 side)
B47 How does a theory become an accepted fact?
B48 Germs and you (2 sides)
B49 Alcohol (1 side)
(1 side)
Section B8 The nervous system and hormones
B50 Stimulus and response (4 sides)
B51 Nerves or glands? (2 sides)
B52 Hormones to control blood glucose (2 sides)
B53 Hormones and cycles (1 side)
B54 Tropisms in shoots (1 side)
B55 Tropisms and plant hormones (2 sides)
B56 Rights and wrongs of using hormones (1 side)
Section B9 Homeostasis
B57 Keeping a steady state (2 sides)
B58 What does dialysis do to blood? (2 sides)
Section B10 Cell division
B59 A model of mitosis (1 side)
B60 Cells dividing (1 side)
B61 A flick book to show mitosis (1 side)
B62 DNA, genes and protein synthesis (3 sides)
B63 Chromosones in sex cells (2 sides)
Section B11 Variation
B64 Variation in people (2 sides)
B65 Variation in ivy leaves (1 side)
B66 Generations of tomato plants (2 sides)
B67 Making an identification key (1 side)
Section B12 Inheritance
B68 Breeding with beads (2 sides)
B69 Skipping a generation (1 side)
B70 Sex-linked inheritance (1 side)
B71 Two inherited diseases (1 side)
B72 Genes (1 side)
B73 Genetic engineering (1 side)
B74 Genetic engineering - the issues (1 side)
B75 Cloning a cauliflower (2 sides)
B76 Plant and animal clones (1 side)
B77 Selective breeding (1 side)
B78 Potato cyst eelworm and potato blight (1 side)
Section B13 Evolution
B79 Fossils (1 side)
B80 A theory based on natural selection
B81 How many offspring? (1 side)
B82 Darwin's century (2 sides)
B83 Selection in action (1 side)
B84 Using models to explain selection
B85 New types of flu (2 sides)
(1 side)
(2 sides)
Section B14 The impact of human activities
B86 Patterns in the distribution of a simple plant (1 side)
B87 Investigating plant populations (2 sides)
B88 Red squirrels (1 side)
B89 Types of pollution (1 side)
B90 Monitoring water pollution (2 sides)
B91 Nitrates in water (1 side)
B92 Acid in the air (1 side)
B93 How do pollutants affect Chlorella? (1 side)
B94 Global warming (1 side)
B95 In defence of modern farming (1 side)
B96 Plant protection in Thailand (2 sides)

NUFFIELD BIOLOGY
SKILL SHEET - USING A MICROSCOPE
eyepiece
B1
Follow these steps when setting up a microscope.
For a first attempt, you could use a transparent ruler
instead of a specimen on a slide. Find the diameter of
the field of view at each magnification. Use this later,
to calculate the length and width of your specimens.
a Put the microscope slide with your specimen on
the stage. Hold it with the clips. Move the slide
until your specimen is over the hole in the middle
of the stage.
b Turn the nosepiece so that the smallest
objective lens (low power) is in line with the
barrel. It will click into place.
c Looking from the side, turn the coarse
adjustment focusing knob slowly until the
objective lens and microscope slide are as close as
they will go, but not touching.
When looking through the eyepiece do not turn the focusing
knob so that objective lens and stage move closer together.
You might smash the slide or scratch the objective lens
especially if using a high power lens.
coarse adjustment
focusing knob
A compound microscope. Note that the barrel
moves up and down for focusing
barrel
fine adjustment
focusing knob
nosepiece
mirror for adjusting light
reaching the specimen
medium
power
high
power
d Direct light from a lamp on to the
microscope mirror. Look through the eyepiece and
move the mirror until you see plenty of light
brightening up the full field of view.
e Adjust the opening of the iris diaphragm if
the light is too bright or too dim. (You get a better
picture if you don't have too much light.)
Direct light
from the Sun
focused
through the
microscope
can damage
your eye.
f Turn the coarse adjustment focusing knob to move the lens
slowly away from your specimen. Check this by looking from the
side. Keep turning until the specimen comes into focus. Then use the
fine adjustment knob to focus as sharply as possible on the part of
the specimen you want to examine.
iris lever
iris half open
g Move to a higher power lens by rotating the nosepiece. Be very careful that the longer lens holder
does not touch the slide or specimen. Re-focus. You may only need to use the fine adjustment.
(Open the iris diaphragm a little if you need more light.)
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
CELLS AND WHAT THEY DO
B2
In this activity you are going to look at a
variety of animal cells and find out what
they do (their function).
Cells are arranged in blocks, sheets or
clusters, to make tissues. Different tissues
are built up into organs, and organs work
together in organ systems. These systems
each do a different job in a living body
(organism).
these cells mass together
to form an epithelial tissue
these cells mass together
to form smooth muscle tissue
the epithelial and
smooth muscle tissues
combine together in the
wall of an organ such as
the gut
the gut, with the
liver and pancreas,
make up the digestive
system
To do
a Look at a series of slides of animal cells through a microscope.
You will see that they are more difficult to interpret than plant cells,
because they don't have a wall.
b Use pictures in textbooks to help you to work out what you are
looking at.
all the systems
together make
up a living
organism
To record
• Make a drawing of each of the cells you look at.
• Write short notes about each cell explaining how its structure suits its
function. Talk about their shape, for example, long and thin, cuboid, discshaped
etc; any special organelles such as cilia; any particular chemicals
such as haemoglobin in red blood cells.
© in this format Nuf field Foundation 1996 Diagram based on Roberts, M B V, Biology for Life, Nelson, 2nd edition, 1986

NUFFIELD BIOLOGY
BODY SYSTEMS IN DAPHNIA
B3
Think about the characteristics of living things. Most animals and plants share out these activities among
their different systems. They have systems for feeding, breathing, reproducing, excreting, and so on.
In this activity you can look for some of the body systems in an animal called Daphnia. Daphnia is a
freshwater animal, a crustacean related to shrimps, crabs and woodlice.
Todo
Investigate Daphnia in one or more of these ways:
• observe them in a beaker of water,
• examine them with a microscope,
• study their responses to changes in their
environment, such as temperature and light intensity,
• read about them in books. If you can't find any
information on Daphnia, you will probably be able to
find out about crustaceans in general.
To record
Describe with a labelled diagram some of these body
systems in Daphnia:
• digestive system,
• blood circulation system,
• breathing system,
• nervous system,
• reproductive system,
• system for support and movement.
If you have time
Study a flowering plant. Try to decide whether it has any systems which are similar to the ones in
Daphnia. Make a table to compare Daphnia and your flowering plant, to show how plants and animals
have rather different ways of supplying the same needs.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
BODY SYSTEMS IN ANIMALS
B4
Todo
The drawings show some of the organs which make up the
body systems of some animals.
• Label the diagrams. Add to your labelling as much
information as you can about the body systems and their
organs. Give each organ a name and say what it does (its job
or function).
• Make a table to show how the structure of each system
helps it to carry out its function.
Elephant
Rat
Earthworm (front end)
1 in this format Nuffield Foundation 1996 Pigs: from Salt, B., GCSE Rural science, vol. I, Cassell, 1980
Rat: from Romer, A. S., The vertebrate body, Saunders, 4th edition, 1970
Earthworm: from Barnes, R. D. Invertebrate zoology, Saunders, 1968

NUFFIELD BIOLOGY
B5
HOW DO GASES GET IN AND OUT OF LEAVES?
To observe
1 Looking at leaves
• Look at some leaves. How are they similar? How do they differ?
• Take a closer look at the parts of a leaf with a hand lens.
To record
• Draw a leaf. Label your drawing to show: leaf stalk (petiole), midrib,
network of veins and leaf blade (lamina).
• What does each part of the leaf do?
• What do you notice about the colours of leaves?
To do
2 Looking for clues
a Bring some water to the boil in a beaker.
Take care
when boiling
water.
b Turn off the gas and wait until there are no more bubbles.
c Pick up a large soft leaf by its stalk with tweezers. Put the blade of the
leaf into the hot water.
d Look closely at the upper and lower surfaces of the leaf.
To record
• What do you see when you put a leaf into hot water?
• Suggest explanations for what you see.
To do
look for bubbles
coming out of
the leaf
the Bunsen
burner is
turned off
3 Taking a closer look Clear nail varnish
a Take a leaf and paint the upper and lower surfaces with clear nail
varnish.
b Wait for the nail varnish to dry.
c Take a small piece of clear sticky tape (e.g. Sellotape) and stick it over
the dry varnish on the lower side of the leaf.
d Peel off the sticky tape. The nail varnish will come off with it.
e Stick the tape on to a clean microscope slide. Label the slide and examine it.
f Repeat c, d and e using the upper surface.
To record
• Make drawings of what you see. • Compare the upper and lower surface of the leaf.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
PHOTOSYNTHESIS
B6
To study
We get sugars and starch from plants. Glucose is the sugar which plants
make by photosynthesis. Glucose is changed into starch and stored.
Study the theory of photosynthesis outlined in this box.
Photosynthesis
energy from sunlight is
transferred by chlorophyll
to energy in food
carbon dioxide
diffuses through
tiny holes in the
surface of the leaf
called stomata
water
from
the soil
water travels up
tubes in the stem
^
Carbon dioxide and water are the raw materials for photosynthesis.
Plants take in carbon dioxide from the air and water from the soil.
Photosynthesis is a process which happens in a series of steps. Energy to make the reactions work comes
from the Sun. Chlorophyll is a green pigment which 'absorbs the light from the Sun and transfers the
energy during photosynthesis.
Plants make glucose first and then change this sugar into starch, which is stored.
Questions
1 Where does the energy for photosynthesis come from?
________
2a Why can we use a starch test as evidence of photosynthesis?
b Does finding starch in part of a plant show that photosynthesis happens in that part of the plant?
3 Make a list of the factors (variables) which you expect to affect the rate of photosynthesis.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
SKILL SHEET - TESTING FOR STARCH
B7
The iodine test
We use iodine solution to test for starch. You quickly get a dark blue or
black colour if you mix iodine solution and starch. A yellow colour means
that there is no starch.
Testing a leaf for starch
The colour in a leaf makes it hard to see what happens when you do this
starch test on it. You can use ethanol to extract the green colour
(chlorophyll) before you add iodine solution. (Care! ethanol is highly
flammable.)
a Carefully remove the leaf you want to test.
b Your teacher will pour some boiling water from a kettle into a beaker.
c Pick up your leaf with forceps and hold it in the hot water for about a
minute. This kills the leaf and breaks down the cell membranes so that the
large molecules of chlorophyll can escape.
d Push your leaf to the bottom of a large testtube
(boiling-tube) and just cover it with
ethanol. Add a few anti-bumping granules.
e Stand the tube with the leaf and ethanol in
your beaker of hot water. The ethanol will start
to boil. You will see the ethanol turning green as
the chlorophyll dissolves in it.
h Look to see if any parts of the leaf turn blue/black.
anti-bumping
granules
f Take your leaf out of the
tube and rinse it in cold water.
boiling
ethanol
g Put the leaf flat in the Petri
dish. Add dilute iodine solution
with a pipette. Make sure that
iodine spreads over the whole
leaf.
hot water
leaf
(folded up)
forceps
kill in
boiling
water
Make sure
that the
beaker is not
more than
half-full.
Your teacher will
tell you what to
do with the green
ethanol solution.
Iodine solution
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
PLANTS WE EAT
B8
garlic
tomato
asparagus
Plants are important in our diet. Rice, potatoes and bread (made from
wheat) all come from plants. You may not like eating green vegetables,
such as spinach or cabbage, but you probably enjoy fruits such as apples,
dates, apricots, melons and mangoes.
To do
a Look at a collection of plants and parts of plants.
• Name the plants from which your specimens came.
• Which parts of the plants do we eat?
b Test parts of the plants to see if they contain starch.
Skill sheet B7 -Testing for starch shows you how to do
this. Record your results.
To record
do not
attempt to
eat any of
the plant
material
• Make drawings of some parts of plants we eat: roots, stems, leaves and
flowers, fruits and seeds. Label your drawings. Alongside each drawing
write a short note to say what that part does in a living plant - its function.
Think carefully. The pictures show a number of things which we call
vegetables but some of them are fruits.
lettuce
peas (in pod)
potatoes (on plant)
corn-on-the-cob
Questions
1 Why are plants important in our diet?
2 If the part we eat is an important food store for the plant (such as peas or
potatoes) say when the plant would use that food if we didn't eat it first.
3 What can vegetable gardeners do to make sure that the edible part of their
crops is as large and tasty as possible? Give one or two examples.
4 Why do we often have to prepare and cook the plants we eat to make
them taste better?
5 Which parts of plants do you most enjoy eating: roots, stems, leaves,
flowers, fruits or seeds?
If you have time
6 Find out why a vegetarian diet should include a wide range of plant
foods, such as pulses, cereals, and nuts.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
DO PLANTS AND ANIMALS ALTER THE
ENVIRONMENT AROUND THEM?
B9
Todo
a Take eight flat-bottomed tubes, or boiling-tubes in a rack.
b Fill each tube to about 2 cm from the top with distilled water containing an
indicator that will detect changes in carbon dioxide concentration.
c Put water plants and water animals into six of these tubes as shown in the
diagram. The other two tubes just have water.
d Now cover the top of each tube with a bung.
e Place tubes A, B, C and D in continuous light and put tubes E, F, G and H in
the dark. Leave them for the same length of time.
Before you come to any conclusions based on the indicator colour, you may find
it helpful to compare the colours of the indicator in the ready-prepared tubes with:
• laboratory air,
• laboratory air with extra carbon dioxide,
• laboratory air with the carbon dioxide removed.
f Note the colour change of the indicator, if any. Record your results by copying
and completing the table. You need to decide whether each tube has more or less
carbon dioxide than it started with.
Light or dark
Animals
Plants
Colour of indicator
Carbon dioxide concentration
compared with lab air
Photosynthesis
Respiration
Questions
A
light
s
X
yellow
more
no
yes
B C D E F G H
1 What can you conclude about the exchange of carbon dioxide between
animals and plants in the light?
2 What can you conclude about the exchange of carbon dioxide by plants in
the light and in the dark?
3 Think about the equations for respiration and photosynthesis. With the help
of these equations, copy and complete the sentences below. The missing
words are: night, oxygen, green, animals, respiration, food.
The amount of ............ and ............ made by photosynthesis in the
............ parts of plants, in daylight, is enough for the ............ of the
whole plant and all ............ in the day and ............ .
© Nuffield Foundation 1996
A
in light
C
in light
E
in the dark
G
in the dark
B
in light
D
in light
F
in the dark
H
in the dark

NUFFIELD BIOLOGY
WHAT AFFECTS THE RATE OF
PHOTOSYNTHESIS?
B10
At a water-garden centre you can buy varieties of pond plants called 'oxygenators'. You buy them
to make sure that there is plenty of oxygen dissolved in the water for fish and other animals.
Todo
a Set up this apparatus in a darkened room with a
light source about 10 cm from the beaker. You will
see a stream of bubbles coming from the cut end of
the pondweed. The bubbles are mainly oxygen.
The number of bubbles in a minute is a way of
measuring the rate of photosynthesis.
b Count the number of
bubbles you see in 1 minute.
They may be too fast to count.
You could then put a row of
dots on a sheet of paper, one
for each bubble. Count the
dots later.
bubbles of oxygen
^beaker
water
Take care
when using a
scalpel.
pondweed weighted with paper clip
I t_____/____.._________________
water to absorb heat so that the temperature around
the pondweed stays the same
- metre rule
c Move the light to 15 cm away. Wait 2 minutes and then count the bubbles again. Repeat this at
20 cm, 25 cm and then at 5 cm intervals until the bubbling stops.
As you moved the light away the bubbles were slower; there was less
photosynthesis.
You can use this technique to test the effect of several variables which can affect
the rate of photosynthesis. Here are some of the variables you might study:
• the colour of the light (use coloured filters),
• the intensity (brightness) of the light. Place the lamp at different distances.
This will need to be done in a darkened room.
Use the formula:
Light intensity

NUFFIELD BIOLOGY
FACTORS AFFECTING PHOTOSYNTHESIS
B11
Questions
1 Study this graph which shows the
results of three investigations, A, B
and C. Then answer parts a-d of this
question. Suggest explanations for
your answers.
a Which factors affect the rate of
photosynthesis according to this
graph?
"vT
'E
ZJ
CD
la
ro
ou
t^U
onn
e/j
CD
1 160
00
o"o
Q. 1 ^.U
O)
1 80
40
C
x /^2
X
^^
/
/
X
2 i\ [ i £ 7
Light intensity (arbitrary units)
A 0.13% carbon dioxide, 30 °C
B 0.03% carbon dioxide, 30 : C
C 0.03% carbon dioxide, 20 C C
b The limiting factor in a reaction is the factor which is in the shortest supply. So it
stops the reaction from going any faster, even though all the other factors are present
in excess. In investigation B, which factor seems to limit the rate of photosynthesis
when the rate is below 70 units?
c In investigation B, which factor seems to limit the rate of photosynthesis when the
rate is 75 units?
d In which investigation were the conditions typical of a British garden in early
summer?
2 The data in this table show the results of investigating the growth of pea seedlings
in the light and in the dark. At each stage the investigator took samples, dried and
weighed them. The table shows average values. Use the data to answer the questions
below.
Part of
seedling
Shoot
Root
Whole plant
Dry mass in
the original
seed / g
0.007
0.02
0.25
group A - in the dark
20 days old
0.07
0.02
0.13
Dry mass of seedlings / g
29 days old
0.09
0.01
0.12
group B - in the light
20 days old
0.15
0.03
0.21
V-shoot
—root
29 days old
0.75
0.04
0.82
a Look at the second column. Which structures (not mentioned in the table) make up
most of the mass of the seed?
b Explain the changes in mass of the whole plants in dark and light conditions.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
THE FOOD TUBE
B12
Todo
You are going to make a presentation to try to get across ideas about
digestion and the digestive system. You can use the drawings
on diagram sheets B13 and B14 and notes on this page or others
you find in other books. Have a look at any posters in your room.
They may give you some good ideas. Feel free to add words and
diagrams of your own.
You will have to decide on the age and general knowledge of your
audience. Pick words and diagrams to suit the amount of science
they know.
Decide on the style of what you are going to produce. Will it be for a
textbook, a magazine, encyclopaedia, multimedia presentation or
children's picture book? Will it be a game?
You might like to explain to people what happens when they eat a
meal of fish, peas and chips. This food contains fat, fibre, starch and
protein. Is this a balanced meal? How could it be improved?
Keywords
Parts of the digestive system
anus, appendix, gall bladder,
large intestine, liver,
oesophagus, pancreas, small
intestine, stomach, teeth, villus.
Digestion
absorb, amino acid, bile, blood,
enzyme, faeces, fat, fatty acid,
fibre, glycerol, insoluble,
peristalsis, protein, saliva,
soluble, starch, sugar.
Notes
Digestion breaks down large molecules into smaller ones.
Enzymes speed up digestion. Each enzyme breaks down a
different type of food molecule.
Most absorption of soluble small molecules from the gut
into the blood takes place in the small intestine. Fat
droplets pass into lymph vessels before going into the
blood.
The pancreas releases enzymes which digest proteins. We
call these enzymes proteases. One of them is called
trypsin.
The large intestine absorbs most of the water from
undigested food.
Cellulose is also a carbohydrate with large molecules.
Enzymes produced by the human gut cannot break up
cellulose into sugars.
Fat molecules are big too. They consist of fatty acids joined
in threes to glycerol molecules.
Only small molecules can get through the gut wall into the
blood.
Amylase is the enzyme in saliva. Amylase breaks down
starch.
The gall bladder releases bile. Bile emulsifies the fat,
breaking it up into small droplets. This makes digestion
easier. We call the enzymes that digest fats lipases.
We cannot digest all the food we eat. The large intestine
stores undigested food until it passes out of the anus as
faeces.
Starch and sugars are carbohydrates. Starch molecules are
large - they are long chains of sugar molecules. Enzymes
turn large starch molecules into small sugar molecules.
Proteins have big molecules. Protein molecules are long
chains of amino acids. Enzymes break down proteins into
small amino acid molecules.
Muscles in the wall of the gut squeeze the food inside and
force it along the tube. This is called peristalsis.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
THE FOOD TUBE
B13
Diagrams to show the structure and function of the gut
salivary glands
diaphragm
stomach and intestines
-————_
-————-^
enzymes
waste
(mainly fibre)
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
THE FOOD TUBE
B14
Diagrams to show microscopic structure of the gut and digestion of food molecules
mucus -
membrane
lining
folded absorbing layer
of villi (these have an
enormous surface
through which the food
can be absorbed)
longitudinal muscle
circular muscle
glandular layer
very thin
layer to
allow easy
passage of
food molecules
lymph vessel to
collect fatty acids
and glycerol
from the gut
capillaries to collect
amino acids, fatty
acids and simple
sugars from the gut
A small section of the gut
lymph vessel
-" 0(/WWWV\AA/\A/
wall of
gut
food
eaten
-v fats ^5^Vfatty acids + glyceroU
down
vitamins •
minerals- broken down
-*• proteins ^^*^~*- amino acids-;
-*• starch —~^—^+broken
glucose
.
-i
down
->• water ——
waste
(mostly fibre)
-to bloodstream
blood vessel
starch - thousands of sugar
units in a chain
• A _
protein - a long chain of amino acids
o
glucose-a
one unit sugar
-oo- maltose-a
two unit sugar
amino acids-there are
about twenty
different amino acids
in proteins
fat glycerol fatty acids
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
ENZYMES AND DIGESTION
B15
This experiment shows why your body has to digest food. You are going to use Visking
tubing. This tubing is made of cellophane, which behaves very like the wall of your gut.
Amylase is an enzyme that helps to digest food. Amylase helps to break down big starch
molecules into smaller glucose (sugar) molecules. It is found in saliva in your mouth and in
pancreatic juice in your duodenum.
To do
Work with four other people to set up the tubing in four boiling-tubes or small beakers.
Share your results.
a Moisten four 15-cm lengths of Visking tubing in water. Open up the softened tubing.
b Tie a knot in one end of each piece of tubing.
c Fit the cut end of a syringe into the open end of the Visking tubing, as in the diagram.
Fix it with an elastic band.
d Carefully fill up the four pieces of Visking tubing with these different
solutions:
tube 1: starch solution tube 3: starch solution and amylase
tube 2: glucose solution tube 4: amylase solution
e Wash the outside of the tubing with running water, then place it in
a numbered boiling-tube of water at about 37 °C (see the diagram).
f Keep this water at 37 °C by standing the boiling-tube in a water bath.
g Wait for 15 minutes, then use a pipette to remove two samples
from the water in each boiling-tube. Test one sample for starch, and
the other for sugar.
Test for glucose
Either: dip a Clinistix test strip into the solution or transfer some of the
solution into a test-tube and use Benedict's test.
Test for starch
Add some of the solution to a little iodine solution.
boiling
tube
Iodine solution
Benedict's solution
•'mouth' of
model gut
elastic
band
visking
bag
knot
beaker
of warm
water
To record
Draw and label a diagram of the four boiling-tubes with the Visking tubing in them.
Record your results in a table.
Questions
1 In this investigation the Visking tubing represents the gut wall. What does the water
at 37 °C represent?
2 How do you explain what happens in each of the four tubes?
3 Imagine yourself the size of a molecule watching the changes in tube 3. Draw a diagram to show what
you see.
4 Why does the body need enzymes to digest starch?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B16
MORE ABOUT DIGESTIVE ENZYMES (SIDE 1)
There are very many chemical reactions going on all the time in your body. Enzymes speed
up these chemical reactions. Each reaction has its own enzyme.
Amylase, trypsin and lipase are enzymes that speed up digestion. Amylase digests starch.
Trypsin helps to digest proteins. Lipase helps to digest fats. Amylase digests starch. But
remember that most of your enzymes are inside your cells. There are thousands of enzymes
in every cell, a different one for each biochemical reaction.
Trypsin
Trypsin is an enzyme that helps to break down proteins to amino acids.
This diagram shows a way of seeing what trypsin can do to the protein which
sticks the silver salts to a black and white photographic film.
The protein is insoluble. Digestion breaks up the protein into amino acids which
are soluble. If you try this experiment you will see that the black silver salts fall
off, leaving the transparent film.
Amylase
Amylase is an enzyme in saliva that breaks down starch to sugars. The diagram
shows one way of keeping track of the reaction. Starch gives a deep blue-black
colour when added to iodine solution. Sugars do not do this.
wooden spill,
split at the
end to hold
the film
strip of
exposed
photographic
negative
warm
water
trypsin
solution
2ml
starch
solution
heat water bath
to chosen temperature
place
tubes
in
position
-2ml
enzyme
solution
after five minutes
pour enzyme into
starch and shake
start clock
every five
minutes from
then on.....
put one drop
of mixture on
dropping tile
using a clean
glass rod
test with
iodine
solution
Lipase
Lipase breaks down fats into fatty acids and glycerol. This diagram shows how
you can use an indicator to show up the digestion of fats.
Phenolphthalein is an indicator that is pink in alkaline solutions of about pHlO. It
turns colourless in less alkaline solutions below pH 8.3. In this experiment the
pink solution becomes colourless when digestion of fats produces enough acid to
bring the pH below 8.3.
To do
Design and carry out an investigation of enzymes using trypsin, amylase or lipase
as your example.
If you have time
1 Why can each enzyme speed up only one particular reaction? Use textbooks
to discover a 'model' which can help us to understand how enzymes work.
2 Digestive enzymes are produced in an inactive form which does not start to
work until it is mixed with an activatior. Suggest why this is important.
stirring rod
1 ml lipase
solution
add in turn:
5 ml milk
7 ml sodium
carbonate
solution
5 drops of
phenolphthalein
stir and start timing
when you add the
lipase
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B16
MORE ABOUT DIGESTIVE ENZYMES (SIDE 2)
Here is a way to get started with your enzyme investigation. You are going to use
the enzyme called trypsin to digest egg white. Egg white contains a lot of protein.
To do
a Label two test-tubes A and B. Put 5 ml of trypsin solution into each tube. Also
put 5 ml sodium hydrogencarbonate solution into each tube.
b Cut two 0.5-cm cubes of egg
white. Chop one of the cubes into
small pieces. Put the uncut cube into
tube A. Put the chopped up cube
into tube B. Stir the tubes gently
with a glass rod.
c Stand both test-tubes in a beaker
of water at 40 °C. You can keep the
water warm by wrapping the tube
with insulating material.
insulating
material
d Every 5 minutes take the test-tubes out of the beaker and look at them. Rock
them gently. Look for signs that the enzyme solution is digesting the protein.
Make observations for about 30 minutes.
To discuss
1 Think about the design of this experiment.
• What is the question that this experiment is designed to answer?
• What is varied in the experiment to test the question? (The independent or
input variable.)
• What do you observe or measure? (The dependent or outcome variable.)
• What is kept the same? (The control variables.)
2 What do your observations tell you? (What is the answer to the question that
this experiment is designed to answer?)
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
THE VALUE OF VILLI
B17
To read
One way to understand the importance of villi in digestion is to compare people
who have them with people who do not. It is estimated that 26 000 people in
Britain suffer from coeliac disease. The lining of the small intestine in people
who have this disease is damaged by a substance in the food called gluten. Gluten
is a mixture of proteins found in some cereal grains used to make flour. As a result
of this damage, the sufferers' villi do not function.
The data in the table show the heights at different ages of two boys. One boy had a
normal gut and the other had coeliac disease. The parents of the boy with coeliac
disease were unable to provide their son with the proper diet. He was only given
the correct diet when in hospital or when recovering at home under supervision.
Eventually he learned to treat himself and remained well.
Age / years
1
2
4
7
8
10
12
14
15
To do and questions to answer
Height of boy with
normal gut / cm
75
83
99
120
126
137
147
159
166
1 Plot a graph of the height of both boys against their age.
Height of boy with
coeliac disease / cm
2 Between which ages do you think it likely that the boy with coeliac disease was
on the wrong diet?
3 Calculate the rate of growth in centimetres per year for both boys between 5 and
8 years of age.
4 How much faster did the boy with a normal gut grow in this three-year period
compared with the boy with coeliac disease?
5 How convincing do you think these figures are? Could the survey have been
improved?
6 What effect would you expect coeliac disease to have on someone's health?
7 What treatment would be most suitable for a person who has this condition?
© Nuffield Foundation 1996
60
70
87
100
102
115
125
135
145

NUFFIELD BIOLOGY
FOODS AND FOOD TESTS
B18
1 Foods
To do
Draw lines between the rows of boxes to show how we use each nutrient in our body
and to show whether it needs to be digested. Two lines have been drawn for you.
2 Food tests
To do
Fill in the table to give a summary of the methods for testing foods.
Nutrient
Solution(s) used
Original colour
Is heat needed?
Final colour, if the
result is positive
Examples of foods
with a high
percentage of the
nutrient
Starch Simple sugars Fat Protein
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B19
LOOKING AT THE HEART (SIDE 1)
The heart you examine should have the blood vessels still attached, although
sometimes butchers cut these off. They may even remove the tops of the atria
and cut into the ventricles, so you must bear this in mind as you carry out this
investigation.
In this investigation there are many things for you to do and record. So make
sure you read the instructions carefully before you start.
Part 1: The external structure of the heart
biohazard
To do
a Note the general shape and size of the heart. (It will probably have come from
a sheep.) Measure its size, its mass and its volume.
b Identify the atria and the ventricles.
c Try to work out which is the right side of the heart and which is the left.
Write down how you came to your decision.
d Note the thick-walled, rubbery arteries attached to the heart. Note also the
much thinner-walled veins. Feel inside these vessels with a finger; feel the
texture and the strength of both types of vessel. Try to describe what you can
feel.
e Examine the thin-walled veins that carry blood into the atria.
f Look inside the main arteries and veins. If you can see any structures attached
to the walls, try to decide what they are, what they might do and how they could
work.
g Examine the surface of the heart for blood vessels.
h Observe and record the colour and texture of the different parts of the heart.
• Wash your hands with warm water and soap after handling animal material.
Questions
1 Suggest a function for the blood vessels that run over the surface of the heart.
2 What would happen if a branch of one of these vessels became blocked?
3 How do the atria differ in appearance from the ventricles?
4 The walls of the aorta and of the pulmonary artery are not equally thick.
Which one has the thicker walls?
5 One of the ventricles is also thicker than the other. Find out which it is.
6 Suggest a reason for this difference in thickness.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B19
LOOKING AT A HEART (SIDE 2)
Part 2: The internal structure of the heart
aorta -
aorta (opened)
pulmonary artery
pulmonary artery
line of second
cut
right atrium
line of first cut
right ventricle
left atrium
left ventricle
cut wall of
left ventricle
Todo
i Make a long vertical cut down the aorta and the
left ventricle to the apex ('tip') of the heart. Be
careful. The drawing above shows you where the
cut should go. The position of the blood vessels on
the surface of the ventricle will help you to make
your cut in the right place.
j Pull the edges of the ventricle apart and examine
the inside of the ventricle and the aorta. Inside the
aorta you will be able to see more clearly the
structures referred to in step f on side 1. Examine
them carefully and look at question 7.
k Carefully cut upwards into the left atrium. The
line to cut is shown in the drawing above. Pull back
the edges of the atrium. Measure and record the
thickness of the wall of the atrium and the wall of
the ventricle.
1 Carry out a similar examination of the right side
of the heart.
m Carefully examine the structures that lie against
the walls of the heart where the atrium joins the
ventricle. These structures are the valves separating
the two chambers of the heart. You should be able
to see very thin flaps of tissue, with thin 'threads'
attached to the base of the flaps. How many threads
are there on each side of the heart? Can you work
out how these valves operate?
• Wash your hands.
Questions
7 The structures inside the base of the aorta are valves. Write down their function and an explanation of
how they might work. (Note there are no similar structures at the place where the main veins join the atria.)
8 Make a table comparing the two sides of the heart, using the features you have observed and measured.
If you have time
9 The threads attached to the valves between the atrium and ventricle are not very stretchy. Why is this
important for their function?
10 These threads are made of the same material as tendons, 'a protein called collagen. Tendons attach a
muscle to a bone. Why is it important that they do not stretch?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B20
WHAT DOES THE HEART DO? (SIDE 1)
Blood leaving the lungs has more oxygen in it than when it
gets back to the lungs. Where does this extra oxygen go?
How does the blood get around the body? How does a
good supply of oxygen get to every living cell in your
body?_____________________________
Your teacher may show you an animal's heart. You may
prefer to watch a video. A computer program linked to
sensors and a data logger can allow you to watch animated
graphics beating in time to your heart.
To do
Use what you have seen and a textbook to complete the
diagram sheet (side 2).
a Look at diagram I on side 2 showing the heart pumping
blood to the lungs. Colour bright-red the blood with a lot of
oxygen. Colour dull-red or blue the blood that has less
oxygen. Label the atria, ventricles and valves in the heart.
b Look at diagram n showing the heart pumping blood to
the rest of the body. Colour the blood as in part a.
c The heart is a double pump circulating blood to the lungs
and to all the other organs in the body. Colour the blood in
diagram HI as in part a. Don't forget the blood inside the
heart.
d Look at diagram IV showing the circulation. The parts
that look a bit like nets are very small blood vessels called
'capillaries'. Blood from arteries in the organs flows into
the capillaries. A network of capillaries in every organ
carries blood close to all cells.
capillaries
in head
heart
capillaries
in lung
liver
intestine
Colour the blood - again using bright-red for blood rich in oxygen and
dull-red or blue for blood with less oxygen. What colour will you use for
the blood in the capillaries?
.—— blood with a lot of oxygen
—— blood with little oxygen
—- direction of blood flow
J_left lung
kidney
capillaries
in arm
and hand
capillaries
in leg
and foot
Question
1 Try to answer the questions in the box at the top of this page.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B20
WHAT DOES THE HEART DO? (SIDE 2)
2 Fill in the gaps in the sentences below. Use these words: large, arteries, away,
pressure, capillaries, heart, arteries, arteries, veins, heart, vessels, heart.
In the circulatory system there is blood, a pump called the ............ and tubes called blood .............
The tubes that carry blood ............ from the heart to body organs are called ............. The tubes that
carry blood to the ............ from the body organs are called ............. Blood in organs flows from
............ to veins through very narrow tubes called ............. The total volume of all the capillaries is so
............ that the blood pressure in them falls. So the blood must go back to the ............. where its
............ will rise, to force it through the ............ again.
arteries from
heart to lungs
left ventricle
pumps blood
around body
in arteries
right ventricle
pumps blood
out of the heart
into an artery
blood passes
along a vein
back to left
atrium
artery to the lungs
aorta
veins pass blood
back to the vena
cavaandthento
the heart
lungs
'i
IV
vena cava
(vein from
body)
lung
head
and arms
^pulmonary
artery
(to lung)
.pulmonary
vein
(from lung)
left atrium
left ventricle
vein from lungs
. _ artery to body
tissues
right atrium
right
ventricle
vena cava_,.
(vein from
body)
left
ventricle
intestine
.aorta
vein from body tissues
the body
• Starting at the lungs, use your finger to trace the route the blood takes until it
gets back to the lungs again. How many times did you pass through the heart?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
WHAT HAPPENS IF YOU HAVE A HEART
ATTACK?
B21
aorta
Your heart pumps blood around your body. Blood carries
the food and oxygen needed by all living cells - including
the muscle cells which make up the wall of the heart.
Your heart has a thick wall made of muscle.
pulmonary artery
right atrium
left atrium
coronary artery
Heart muscles are made up of living cells too and they work
hard. They need oxygen and food, just like any other cells.
So the heart pumps blood to its own muscles through the
coronary arteries. A blockage in one of these arteries leads to
a heart attack.
right ventricle
left ventricle
Questions
Use reference books, leaflets on healthy living and up-to-date first-aid manuals to
help you to answer these questions.
1 What are the symptoms of a heart attack?
2 How would you help someone if you thought they had just had a heart attack?
3 What kind of person is unlikely to have a heart attack?
4 How do coronary blood vessels get blocked?
5 What causes the agonizing pain during a heart attack?
6 An enzyme called streptokinase is sometimes used to treat someone who has had
a heart attack. How can streptokinase help?
7 How do doctors find out where the blockage is in the heart?
8 Describe how doctors can do something about blockages in coronary arteries.
Try to give three different ways and include diagrams to help your explanation.
l)
normal artery
If you have time
blocked artery
9 What does the heart's natural pacemaker do? If the pacemaker is damaged in a heart attack, an artificial
pacemaker must be fitted. Find out how this works.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY_____________B22
BLOOD AND BLOOD TRANSFUSIONS
Todo
The Vampire's nightmare!
a Label two test-tubes 1 and 2. Put 10 ml of artifical 'blood' in each test-tube.
b Put 1 ml of water in test-tube 1. Put 1 ml of artifical 'blood clotter' in test-tube 2.
Shake the tubes carefully.
c Put both tubes in a container of water at about 38 °C for about 20 minutes.
Keep the water warm.
d Decide how to record your observations.
e After 20 minutes look at the tubes. Do not shake them. Tip contents of tubes 1
and 2 into two dishes.
To record
• Record clearly the set of observations.
Questions
1 How could you tell that the 'blood' had clotted?
2 Why was 1 ml of water added to test-tube 1?
3 What was the 'blood clotter'?
When people donate blood it is tested for A B O blood groups. This is done to
make sure that people get the correct blood when they need a blood transfusion.
They must not be given blood that will clot in their veins.
To discuss
• In a National Blood Service leaflet it says Group O blood may seem
ordinary - but to us it is very special. Discuss with a partner why it is
ordinary and why it is special. Make a record of your discussion.
Todo
Less than 10 % of donated blood is used whole. The rest is divided into various parts.
Read about Charles and Jenny, then make a list of the parts of blood which they received.
syringe
goggles
hot water
thermometers
blood clotter
g |ass breaking when
shaking tubes
CHARLES suffered severe burns to his back and arms when his Mini caught fire after a collision with a lorry on the M25.
His body lost many litres of fluid containing protein through the burned area of skin. This was replaced by a transfusion of a
total of 6 litres of albumin solution whilst he was in the burns unit of his local hospital. Albumin solution is made
from the plasma from many blood donations, purified and heat treated to prevent the spread of infection.
JENNY is now seventeen and studying for her A-levels. Three years ago she developed leukaemia. Fortunately her older
brother Peter was found to be a suitable bone marrow donor for her and so she had a bone marrow transplant two years ago.
Whilst waiting for the transplant to 'take' Jenny needed daily platelet transfusions for twenty days - each day she received the
platelets from five donations. Nine donations of red cells were also needed during that time.
To discuss
Donor lymphocyte transfusions are an experimental way of treating leukaemia. Do you think that the
National Health Service should pay for an experimental treatment like this?
© in this format Nuffield Foundation 1996
Extracts about Charles and Jenny taken from National Blood Service leaflet and reproduced by permission.

NUFFIELD BIOLOGY
LOOKING AT DIFFUSION
B23
You are going to watch diffusion of vitamin C into cubes of jelly
stained blue with DCPIP. The vitamin C will react with the blue
DCPIP to make a colourless compound, so you will know how far
the vitamin C has diffused. You will cut the cubes into different sizes
to see whether this alters the rate of diffusion.
agar jelly disc of depth 2 cm,
taken from the dish (drawn to scale)
You will be given a dish in which there is a 2 cm depth of clear
jelly. Cut out two cubes of jelly with sides 2.0 cm long. Be
careful.
(There will be enough jelly in the dish for several groups to use.)
b Leave one cube intact and carefully cut the other one to make eight cubes
each with sides of 1.0 cm.
c Leave one of these intact and carefully cut another to make eight cubes
with sides of 0.5 cm.
d Place one cube of each size in a small beaker and cover them with
vitamin C solution. Leave for 5 minutes and watch what happens.
e Pour the solution off into another beaker. Quickly wash the surface of
the cubes with water and dry them thoroughly with blotting-paper.
1-cm cube
2cm
2cm
one 2-cm cube will provide 8 1 -cm cubes
0.5-cm cube
2cm
one 1-cm cube will provide 8 0.5-cm cubes
f Cut each cube in half and examine the newly cut surfaces. Make a drawing of each surface showing
how far the vitamin C solution has penetrated. In each case measure the distance it has travelled.
g It would be a good idea to repeat the investigation to get more results so that you could obtain an
average.
Questions
1 How far has the dye moved into each cube?
2 Which size cube is more completely penetrated by the dye?
3 Complete this table.
The surface area / cm2
The volume / cm3
The ratio of surface area: volume
The ratio of volume:surface area
4 How do the dye molecules move into the cubes?
Large cube
22 x 6 = 24
23 = 8
24/8 = 3
8/24 = 1/3
Medium cube
Small cube
5 Use the table to decide on one factor that would increase the rate at which the dye moves into the cubes.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
WATER IN AND OUT OF CELLS
B24
Animal cells behave very differently from plant cells, when placed in
solutions of different concentration.
Questions
1 Explain these observations with red blood cells. The drawings show what
the observer saw when looking at samples through a microscope.
pipette
distilled
watei
drop of
blood
microscope slide
0.85% sodium
chloride solution
& /
3.0% sodium
chloride solution
Slide 1
Slide 2
Slides
a What happened to the red blood cells on each of the microscope slides?
b How do you explain the differences?
c What is the difference between plant and animal cells that helps to explain
what happens when red blood cells are mixed with distilled water?
d Forensic scientists can tell whether people have drowned in fresh water or
sea water. They do this by examining the blood in the lungs. How do you
think they can tell?
2 People suffering from cholera become very dehydrated. They are treated
with a saline drip which puts salt solution directly into their blood.
a Why are they not given pure water?
b What do you think will be the concentration of the salt solution?
3 Jam has a very high sugar concentration (about 50%). What do you think
will happen to the cells of any bacteria or fungi which land on some jam?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
OSMOSIS AND TURGOR
B25
In this activity you can see that cells are very
sensitive to the concentration of dissolved
chemicals in the water around them. You are going
to use cells from a red onion or a rhubarb stem.
The red liquid in the cells makes it easier to see
what happens.
To do
a If you are investigating red onion cells, peel off
a very thin piece of onion tissue from an inner
layer. Try to get a strip which is only one cell
thick.
If you are using rhubarb, peel a piece from the
epidermis.
b Place the strip on a slide and cover it with a
drop or two of distilled water. Add a cover slip.
c Look at the cells through a microscope. Start
with the low power lens. Refer to Skill sheet B1
(Using a microscope) for help.
d Take another strip of cells from your plant
material. This time mount it on a slide with
concentrated sugar solution. Examine it through a
microscope as before.
red onion
cut in half
mount a small
piece in distilled water
e After a few minutes draw out the sugar solution with a piece of filter paper and
replace it with distilled water. Now see what happens to the cells.
To record
. remove one of the inner fleshy leaves
each layer has a red epidermis
after a few
minutes
Describe what you see as you examine onion or rhubarb cells in water and in sugar solution.
Drawings will help you to record your observations.
Questions
1 What limits the amount of water that can be taken into a plant cell?
2 What decides whether there is more water flowing into or out of a cell?
3 Why do plants 'wilt' when they are short of water?
use filter paper
to draw out the
sugar solution
replace with distilled water
4 Plant cells make soluble glucose by photosynthesis. They change the glucose into
insoluble starch for storage. Why is this important for the 'water balance' in plant tissues?
use tweezers to pull
off a thin strip of red
epidermis from the
outer side of the leaf
mount another piece in
sugar solution
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B26
ACTIVE TRANSPORT (SIDE 1)
Here is an account of an experiment performed some years ago by scientists
investigating active transport. Study the data on side 2, then answer the questions which
follow them.
The method that was used
a Two similar groups of barley seedlings were grown from seed in a culture solution.
(A culture solution contains all the necessary ions for plant growth.) The sulphate ions
in the solution contained radioactive sulphur atoms, 35S.
b During the experiment oxygen was bubbled through the solution containing one
group of seedlings and pure nitrogen was bubbled through the solution containing the
other group of seedlings. Nitrogen gas is not harmful to seedlings, but bubbling it
through the culture solution removes all the oxygen from that solution.
seedlings
oxygen
nitrogen
roots go through
hole in cork
culture solution
c The amount of radioactive sulphate ions in each culture solution was measured at the
start of the experiment and then every half-hour for 4 hours.
d The investigators subtracted the amount of radioactive sulphate ions remaining in
each solution from the amount that was there at the start of the experiment. They
assumed that the difference between the two figures showed the amount of sulphate ions
which had been taken up by the plant.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B26
ACTIVE TRANSPORT (SIDE 2)
The table shows the results for each solution.
Time/
minutes
0
30
60
90
120
150
180
210
240
Total amount of sulphate ions absorbed /
arbitrary units
With oxygen
(aerobic)
0
220
290
350
390
430
490
500
530
Things to do and questions to answer
With nitrogen
(anaerobic)
0
140
190
210
225
238
250
260
290
1 Plot a graph of these results. Put the time on the horizontal axis.
2 In which solution did the barley take up the most sulphate ions?
3 Make a simple statement that links the amount of sulphate ions taken up to the
amount of oxygen available to the plant.
4 What process, which uses oxygen, takes place in the roots of a plant?
5 What is released by this process?
6 Suggest why giving roots plenty of oxygen affects the uptake of sulphate ions.
7 Put into your own words what is meant by active transport.
8 We can say that active transport is different from diffusion because the ions are
moving up their concentration gradient. What do you think this means?
9 Use the conclusions you drew from this experiment to explain each of the
following observations.
a Over-watering pot plants may kill them.
b Many fields cannot be used to grow crops successfully unless drainage ditches
are dug around them and drainage pipes laid through them.
c Very few species of plant grow in bogs and marshes.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
A SUMMARY OF MASS FLOW, DIFFUSION,
OSMOSIS AND ACTIVE TRANSPORT
B27
To do
Draw lines between the rows of boxes to explain the four processes.
Two lines have been drawn for you.
Then write an example of each process.
All particles move
together at a
similar rate
Individual particles
move randomly
Energy released by
respiration is needed
for movement of particles
from higher concentration
of those particles to a
lower concentration (down
their concentration gradient)
from lower concentration
of those particles to a
higher concentration (up
a concentration gradient)
Mass flow
Diffusion
Osmosis
Active transport
ftg.
e.g.
e.g.
e.g
A selectively permeable
membrane is essential
for this to happen
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
MINERALS FOR PLANT GROWTH
B28
Farmers and gardeners grow bigger crops by adding fertilizers to the soil. Carry out an investigation to see
for yourself how a lack of minerals can affect plant growth.
To do
Work with other groups to save time and to cut down on the amount of apparatus needed for the class.
You will be able to use these culture solutions:
• a complete mineral culture solution with everything plants need for growth,
• a series of culture solutions which are complete except for one mineral ion, for example: nitrate,
phosphate, or compounds of elements such as potassium, magnesium, sulphur, calcium, iron and sodium.
These diagrams suggest ways of
setting up the investigation.
Duckweed (Lemnd) - start with
about ten duckweed plants in each
container. Make sure that the total
number of leaves is the same, and
that they appear to be healthy.
Lemna plants
fl°atin 9 clingfilm
culture solution
Green algae - set up labelled flasks,
each with 100 cm3 of one of the culture -gently
solutions. Seal the flasks with plugs of
cotton wool. Use a syringe to add 1 cm3
samples of a culture of algae to each
flask. Stand the flasks in a light place and
look at them from time to time for two
weeks. Examine the algae through a
microscope with high power
magnification.
To record
Seedlings - support seedlings in testtubes
with cotton wool so that their roots
are in one of the culture solutions. Cover
the tubes with aluminium foil or black
paper to keep the roots dark. Stand the
tubes in a rack. Place the rack in a light
place and record the growth of your
seedlings for a few weeks. Top up the
tubes with distilled water from time to time.
tight bung of
cottonwool
cereal
seedling1
test -
o
Remove the plug from flask A. Empty 1 cm0 of tube
culture from the syringe into the flask. Replace
the plug.
culture'
solution
cottonwool
opaque covering
plug_
disinfectant
O
100 cm^ culture
solution
Put the syringe
in disinfectant.
Repeat for flasks B and C. Add
an identical amount of algal
culture to each flask.
• Note the design of your investigation and draw labelled diagrams to show what you do.
• Explain the key points in the design of your investigation.
• Record the observations you make including the colour of the growing plants or algae.
Display your data in a way that will help you to see patterns in the results.
Question
1 What have you learnt from your investigations? Which mineral ions seem to be important
for the growth of the plants you investigated?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
MEASURING THE RATE OF WATER LOSS
FROM LEAVES
B29
The apparatus in the diagram below is called a potometer. It is used to compare the rate
of transpiration in different conditions.
a A leafy shoot was cut, and the cut end was pushed through a bung.
b The cut end of the shoot was cut once more, diagonally, while it was held under water.
c The bung, with the shoot in it, was placed firmly in the top of a flask filled with water,
which was fixed to a capillary tube and scale, as shown in the drawing below.
d As water was lost from the leaves, more water was drawn up into the shoot from the
flask. This drew the air bubble along the capillary tube. The rate at which the air bubble
moved was proportional to the rate at which the shoot was taking up water.
e Every time the bubble reached the left hand end of the capillary, the syringe plunger
was used to move the bubble back to its starting point again. In this way a number of
readings were taken, using the same shoot the whole time and only changing one
condition at a time.
f The table shows the average results for each treatment used.
beaker of
water
Treatment
No special treatment
Increased humidity
Increased wind speed
Rate of transpiration after
treatment in mm / minute
20
15
25
flask full of water
Questions
end of snoot cut
at an angle,
bark removed
retort stand
wooden block
Increased air temperature
Lower light intensity
Removal of 50% of leaf area
1 How do you think the experimenters provided each of the special treatments mentioned in the table?
2 Calculate the percentage increase or decrease in the rate of transpiration produced by each treatment
when compared with the rate obtained without any special treatment. Here is an example worked out
for increased humidity:
Decrease in transpiration rate = 20 - 15 = 5 mm per minute
Percentage decrease = (5 •*- 20) x 100 = 25 per cent
So the rate of transpiration in increased humidity is 25 per cent less than when there was no treatment.
3 Plot a bar chart of the results.
4 Try to give an explanation for each result.
24
18
m
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
WATER FROM ROOTS THROUGH LEAVES
B30
Water travels up tall plants at about the same speed as the lifts which carry people to the top of a tall office
block.
Every day a beech coppice with 400 trees raises about 20 tonnes of water from the soil up to the
leaves - 20 m or so above the ground.
How and why is so much water moved up plants from their roots to their leaves and then out into the air?
Even after many years of studying these simple questions scientists do not know all the answers.
Todo
a Look at a pot plant with its leaves and stem
enclosed in a polythene bag. The plant has stood in a
sunny place for an hour or so.
1 Explain what you see on the inside of the bag.
b Take a close look at a leafy shoot of busy
lizzie or a celery stalk which has been
standing in a dye solution for a while.
polythene bag
Cut across the stem at 1 cm intervals using a sharp blade. Start from the top and work
downwards. Each time, examine the cut surface with a hand lens for signs of the dye.
Work out how fast the dye has travelled up the stem.
c Your teacher will give you a thin slice of stem containing dye. Mount the slice in distilled
water on a glass slide. Add a cover slip and examine the slice through a microscope.
2 Describe what you see.
d Take a look at the two Coleus cuttings
which grew roots in a fertilizer solution
during the last couple of weeks. For the last
l'/2-2 hours one cutting has stood with some
of its roots in a dye solution and the others in
water. The other cutting has stood with some
roots in the dye solution and the others in air.
Look closely at the leaves.
3 Where has the dye got to?
To study
Compare your observations in this activity with
photomicrographs in a textbook.
dye solution
Take care
when using
sharp
instruments.
roots in air
To record
Make a note of your observations. Labelled diagrams will help.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
WHERE DOES AIRGO WHEN YOU
BREATHE IN?
B31
(SIDE 1)
In this activity your teacher may show you an animal's lungs. This sheet suggests
some things to look out for.
You may prefer to look at models or watch a video. A computer program can help
you to see how the rib cage, diaphragm and lungs move as you breathe.
To record
• Describe the feel and colour of the lungs.
• Are they hollow bags or spongy?
• How is the windpipe kept open and yet able to
bend?
• What are the lungs like when full of air?
• Do you have to squeeze the lungs to push the air
out?
• What do the lungs look like across a cut edge?
• Describe how the lungs seem to be built.
• What forces air in and out of your lungs as you
breathe?
• How does the air you breathe out differ from the
air you breathe in?
trachea (windpipe)
lungs
Wear rubber or plastic
gloves if you are going
to touch the lungs.
Todo
a Use textbooks to help you label the diagram of the breathing system on side 2.
Use these words: nostril, rib, diaphragm, bronchus, alveolus, trachea (windpipe),
capillaries (network of very small blood vessels), lung, cilia, bronchiole.
To record
• Complete the sentences on side 2, to explain how your lungs are kept clean.
Use these words: dust, smoking, cilia, 'cell eaters', throat, microbes, trachea,
alveoli, cleaning, bronchi, mucus, alveoli.
• Write down some situations where you might wear a mask over your mouth and
nose. Try to include examples from factories and other places of work. In each
case, say exactly what the mask is filtering out.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
WHERE DOES AIR GO WHEN YOU
BREATHE IN?
B31
(SIDE 2)
air in the trachea
larynx
space occupied
by heart
muscles
the point of a pin
on the same scale
The pipe cleaners
In order to function efficiently the lungs must be kept clean. There are special cells lining
the ............ and ............ whose function it is to make sure that dust particles do not
travel all the way to the delicate ............ .
Specialized cells produce a substance called ............ on which ............ particles get
trapped. The tiny hairs (called ............) which line the tube move the mucus upwards
and out of the trachea into the ............. It is then swallowed. If microbes get past this
first line of defence they will enter the .............. Here they will be met by special cells
called phagocytes ('............'). These cells move about gobbling up ............ . There
are serious consequences if any of the ............ mechanisms of the lung are put out of
action. That is exactly what............ does.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B32
HOW YOU INFLATE YOUR LUNGS (SIDE 1)
Todo
Place your hands at the bottom of your rib cage while you are breathing. Describe
the movements that you can feel. Either write your description down or try to tell
someone what is happening.
To read
inner layer of muscles
(internal intercostal muscles)
sternum
outer layer of muscles
(external intercostal muscles)
The chest movements you felt are caused by the muscles which link each rib with
its neighbours. They are called intercostal muscles. The ones on the inner
surface of the rib cage are called internal intercostal muscles; those on the outside
are the external intercostal muscles. These two groups of muscles are attached
between the ribs at different angles, as shown in the drawing.
Questions
1 Work out which of the two sets of
muscles has to contract to make the chest
volume bigger. You may find the model in
the drawing useful in answering this
question.
sternum
2 The other set is only used when you are
forcing air out. In gentle breathing, this
second set of muscles is not needed. Can you
explain what else is pulling the ribs down?
rib
backbone
elastic band
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B32
HOW YOU INFLATE YOUR LUNGS (SIDE 2)
Changes in the volume of your chest are also
caused by movements of the diaphragm. When the
diaphragm muscle contracts the diaphragm is pulled
downwards. This increases the pressure in your
abdomen. When the diaphragm muscle relaxes the
diaphragm is pushed up by the pressure in your
abdomen. So it becomes arched upwards, as the
diagram on the right shows.
diaphragm
muscle
To do
In this model the balloon represents your lungs and
the syringe your thorax.
a Put your finger over the tiny hole in the syringe
and pull the plunger halfway out. What happens to
the balloon?
coverthishole
with your finger
plunger-pus/i/f
gently in and out
b What structure is represented by the syringe plunger?
c Explain why the balloon inflates when the plunger is pulled out.
Like the balloon, your lungs are also elastic.
• What part does this property play in helping you to breathe?
7
balloon held
tightly by bung
• In what ways is the syringe model an unsatisfactory model of what happens when you breathe?
Cause and effect
Read through this flow diagram.
barrel
Muscles
contract
or relax
Ribs and
diaphragm
move
Volume of
the thorax
changes
Pressure of
the thorax
changes
Air is forced
into or out
of the lungs
Notice that each event causes the next one to happen.
Question
1 Use the flow diagram to help you to write a sequence of events for
a breathing in
b breathing out.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
UNDERSTANDING ASTHMA
B33
Asthma affects about 1 in 10 children and about 1 in 20 adults. The symptoms include a 'tightness' of the
chest, a shortness of breath and coughing and wheezing when breathing. These symptoms are caused by a
narrowing of the tiny air passages in the lungs. These changes are often caused by the presence of an
allergen. Most asthmatics know what is likely to start an attack. It might be house-dust, fur, feathers,
pollen, fungal spores or chemicals such as pesticides. An allergen acts as a trigger which makes the cells
that line the airways swell and produce mucus. Small rings of muscle begin to shorten and make the
airways even narrower. Breathing, especially emptying the lungs, becomes very difficult. Asthma
sufferers can keep a check on the condition of their airways by using a 'peak-flow meter'. This measures
the rate at which they can empty their lungs. A high reading shows that the airways are clear. A lower
reading shows that the airways are getting blocked. Low readings show that it would be wise to use an
inhaler spray such as 'IntaF to try to prevent an asthma attack.
muscle
layer
normal airway
inner
endothelium
allergens in the
airtrigger
receptor cells
What happens in an asthma
attack
mucus
airway shut off leading to
an asthma attack
L
relaxed
muscles
Todo
airway becomes
narrowed so that
breathing is
difficult
a Carry out a survey of your year group to find out how many people have
asthma. Make a note of the things which trigger asthma attacks in your
sample.
• Find out the meaning of the word 'allergen'.
• What were the most common allergens in your survey?
• How could you best display the results of your survey?
b Use a peak-flow meter to find out how lung function varies in
your class. Try to obtain peak-flow readings of different people so
that you can compare:
i) a controlled asthmatic (someone taking medicine to reduce their
asthma),
ii) an uncontrolled asthmatic (or someone with severe asthma),
iii) a 'normal' subject (someone who does not have asthma).
chemicals are
released which
make the muscles
begin to contract
contracted
muscles
Questions
1 Medicines which relax the muscles to prevent the narrowing of the airways are called 'bronchodilators'.
Suggest why they have this name.
2 'Intal' helps stop allergic responses. How is this different from a bronchodilator?
© in this format Nuffield Foundation 1996

NUFFIELD BIOLOGY
INVESTIGATING RESPIRATION
B34
What happens to glucose when it is used in respiration?
In this experiment, some rats were fed with glucose in which the carbon atoms had been
made radioactive. This would not harm the rats. The carbon dioxide they breathed out was
then tested to see if it was radioactive. The experimental and control procedures and the
results of the experiment are shown in the drawing.
1 Rat fed with glucose
from a pipette
rat fed with glucose
containing radioactive
carbon ( 14C)
control experiment
2 Rat's expired air bubbled
through limewater, which
absorbs carbon dioxide
3 Limewater passed through
filter paper
4 Filter paper tested for
radioactivity with Geiger
counter
Questions
radioactivity count: (7\ S7\ /~% /O\ radioactivity count:
8147 units W W ^> ^ 13 units
1 What would have been fed to the control group of rats?
2 Why was the exhaled air bubbled through limewater?
© © © (D
3 Explain why the radioactivity count for the control group of rats was not zero.
4 What interpretations can you make from the results of the investigation?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
HOW MUCH ENERGY IS THERE IN
SOME FOODS THAT YOU EAT?
B35
(SIDE 1)
To do
a Pour exactly 20 cm3 of water into a boiling-tube.
b Clamp the tube to a retort stand (see diagram).
c Measure and record the temperature of the water.
d Find the mass of the dry food and record it.
e Impale the food securely on a mounted needle.
f Hold the food in a Bunsen flame until it starts to burn.
g Immediately put it under the boiling-tube as shown so
that the heat from the burning food is transferred to the
water. Try to direct the flame as accurately as possible.
h Allow the food to burn completely.
i
If it goes out, quickly light it again.
j As soon as the food has burned away completely and
the flame has gone out, stir the water and take the highest
temperature of the water.
k Now calculate the rise in temperature of the water.
-retort
stand
p—boiling-tube
— boilingtube
• You can calculate the energy released from the food using the formula:
energy released from the food / J = mass of water / g x temperature rise / °C x 4.2
Because this figure tends to be large it is usual to express the energy released
in kilojoules (kJ). One kilojoule equals 1000 joules.
• Compare your results with others obtained in the class, using a variety of
foods. Also compare them with the energy values given on food packets ;orin
ir
data tables.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B35
HOW MUCH ENERGY IS THERE IN
SOME FOODS THAT YOU EAT? (SIDE 2)
Questions
1 Why are your experimental figures likely to be lower than those in the tables?
How could you improve the design of your apparatus to overcome this?
2 The next diagram shows a manufactured calorimeter. List the ways in which
this is an improvement to the apparatus used on side 1.
thermometer
to filter pump
heat transfer
coil
water
heatproof
platform
food burning in
nickel crucible
3 Which nutrient - carbohydrate, protein or fat - provides the most
energy per gram?
4 Write a word equation for
a combustion,
b aerobic respiration.
5 Do you think that aerobic respiration would release the same amount of
potential energy from the food as you released by burning it?
6 List all the similarities and differences between combustion and aerobic
respiration.
7a Write a word equation for anaerobic respiration in animals.
b Why does this type of respiration release less energy from food?
c Why do some of our cells sometimes respire anaerobically?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
INVESTIGATING CIGARETTE SMOKE AND
ITS EFFECTS
B36
Todo
a Half-fill two conical flasks with Universal Indicator solution.
b Pack a little cottonwool into two identical glass tubes labelled A and B.
c Record the mass of each tube.
d Fit a cigarette holder into a bung and make sure it is well sealed.
e Now assemble the apparatus as shown in the drawing, preferably in a fume cupboard.
Make sure the tip of the longer tube is below the level of the Universal Indicator in each
of the two flasks.
direction of
airflow
direction of
air flow
lighted
cigarette
cottonwool
unlit
cigarette
Universal
indicator
Universal
indicator
f Turn on the pump and light the cigarette on side A, but not the cigarette on side B.
g When the cigarette has stopped burning, turn off the pump. Record the appearance of
the cottonwool in tubes A and B and the appearance of the indicator in flasks A and B.
h Dismantle the apparatus and find the mass of tubes A and B once more.
i
Tip out the cottonwool and smell it.
Questions
1 What was the change in mass of the two glass tubes?
2 What does the colour of the indicator tell you about cigarette smoke?
3 What type of substances may have changed the colour of the cottonwool?
4 Calculate how much of these substances collected in the tube from the smoke of one cigarette.
5 If this apparatus 'smoked' twenty cigarettes a day for one year, how much material would have
collected?
6 Why was an unlit cigarette included in the investigation?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
SMOKING
B37
A group of teachers has decided to run a health education campaign in their school to do
everything possible to prevent 11-year-olds from starting to smoke (or to encourage them to stop
if they've already started). They have decided to ask the advice of older students in school, and
have come to you for help.
To discuss
Share ideas from your own experience. What can be done to stop younger children smoking?
For ideas look at the opinions together with the facts, figures and information on this page. You
can also use information from health magazines, leaflets from chemists and doctors' surgeries.
To report
Sum up your advice to the teachers in the form of a clear plan. Remember that teachers are busy
people so they will welcome a short, clear statement of all the things you think they should do.
Opinions
• 'Smoking calms your nerves.'
• 'Smoking keeps your weight down.'
• 'Smoking helps you concentrate.'
• 'Smoking makes you feel good.'
• 'Smoking gives you confidence.'
• 'Smoking makes it easier to get on with people.'
• 'Smoking keeps you going when you're tired.'
Facts, figures and information
Children of smoking parents are more
likely to smoke themselves. Children
of parents who smoke are less likely to
smoke themselves if their parents try to
discourage them from starting.
On average, for each cigarette smoked,
a smoker shortens his or her life by
about five and a half minutes.
In 1950 women smoked only half as
many cigarettes per day as men. Now
they smoke almost the same number.
Smoking is the main cause of indoor
pollution. Tobacco smoke contains
about 4000 chemicals. Some of these
chemicals are addictive, some are
irritants, some are poisons, and some
cause cancer.
Smoking kills about 110 000 people
each year in the UK. That is about one
every five minutes.
'Smoking is anti-social.'
'Smoking makes you smell.'
'Smoking makes you cough.'
'Smoking gives you lung cancer.'
'Smoking gives you heart disease.'
'Sharing a home with a smoker can make you ill.'
'Smoking when you are pregnant damages your baby.'
'Smoking when you have a baby doubles the chance of cot death.'
Children under 16 are estimated to
spend up to £90 million a year on
cigarettes. All these sales are illegal as
selling tobacco products to people under
the age of 16 is illegal.
The health care of people with diseases
linked to smoking costs the country
about £500 million a year.
Since the mid-1970s, lung cancer
among women has increased by i
while there has been a 12% decrease in
lung cancer cases among men.
There is evidence that 60% of people
who have one cigarette go on to smoke
more. More than 90% of teenagers who
smoke as few as 3-4 cigarettes are
trapped into a life of regular smoking.
69% of under-age smokers have never
been refused when buying cigarettes.
Smoking among boys is falling. There
has been no decline in smoking among
girls. In 1988, 9% of girls aged 11-15
smoked regularly compared with 7% of
boys. The figures for people aged 15-
16 are: boys 16%, girls, 22%.
From 1972 to 1988, men smokers
dropped from 52% to 33% of the adult
population. Women smokers decreased
from 41% to 30%.
Every year the wood burnt to cure
tobacco consumes trees from 5 million
hectares of land. A tree a fortnight for
the average smoker.
After only 1 year without smoking the
extra risk of heart disease is cut by half.
After 15 years without cigarettes, exsmokers
have almost the same risk of
death as people who have never
smoked.
65% of teenage smokers say they want
to stop smoking.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
ENERGY FLOWS
B38
To study
This diagram shows you what happens to the energy available from
respiration at each stage (trophic level or feeding level) in the food chain.
use and loss of energy resources by plants
use and loss of
energy resources
by herbivores
use and loss of !?

NUFFIELD BIOLOGY_____________B39
FOOD CHAINS AND FOOD WEBS (SIDE 1)
You can best work out a food web as part of a day's field work, or during some types of
laboratory work (such as the study of an aquarium), or a long-term project (like observing
birds in your garden). The ideas that follow are intended to help you design the project
work and analyse your results.
Todo
a Make a list of the plants (or protists) and animals in the habitat you are studying.
Decide which of the different feeding groups (or trophic levels) each belongs to, such as:
• Producers
• Primary consumers
• Higher consumers
• Detritus feeders
• Decomposers
The plants and green protists which produce organic matter, using energy
from sunlight.
The herbivores; you can identify these by their feeding habits, or by
structures such as teeth - don't forget such animals as aphids and snails,
which are also herbivores. Often slow moving, heavily armoured or
camouflaged from predators. Remember that omnivores, which eat plants
and animals, are found at this trophic level and the next.
The carnivores; again behaviour and teeth structure can be helpful, but be
careful when distinguishing between secondary and tertiary consumers.
Usually fast-moving with large eyes and powerful mouthparts to kill prey.
Detritus is decaying remains of plant and animals. It is very rich in muddy
areas such as estuaries. These organisms usually crawl amongst dead and
decaying matter.
Mostly bacteria and fungi, often microscopic.
b Once you have sorted the animals and plants out into their feeding groups, try to work
out some of the links between them.
c Show the links by drawing a food web. You will need to experiment with several
diagrams until you can lay out the names of the animals and plants in a reasonably tidy
and yet logical sequence. Don't forget the decomposers and detritus feeders.
d Connect the names of the animals and plants with arrows showing the directions in
which food - and energy - pass.
e You can practise on the diagram on side 2. Use textbooks to find out what the animals
eat and draw in any extra organisms which you need to complete the chains.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B39
FOOD CHAINS AND FOOD WEBS (SIDE 2)
caddis fly larva
(often found in case) (1cm)
dragonfly nymph (3 cm)
(2 cm)
© in this format Nuffield Foundation 1996 Diagram based on Science at work Ecology, Longman, 1991

NUFFIELD BIOLOGY
BUILDING PYRAMIDS OF NUMBERS
B40
To study
Here are two ways
of picturing the
same food chain.
xk
A
ST** /r* ^R /%*• /^«
On the right is another way of showing a pyramid
of numbers drawn roughly to scale.
We draw the length of the bars more or less to scale
so that they show the numbers of organisms at each
trophic level.
carnivores:
foxes
carnivores: stoats
herbivores: rabbits
tertiary consumers
secondary consumers
primary consumers
Questions
1 Copy this outline and then write in the organisms
in the food chain at the right level.
The organisms are: blue tits, cabbages, caterpillars,
sparrow hawks.
2 Sketch the shape of a pyramid of numbers for a
food chain with these three organisms: fleas, grass
and rabbits.
plants: grass
3 What more does the pyramid of numbers tell you compared with the simple food chain?
4 Here are two sets of data for soil animals from grassland and woodland.
Top carnivores
Carnivores
Herbivores
Producers
Numbers of organisms per 0.1 hectares
grassland
1
90000
200000
1 500 000
woodland
2
120 000
150 000
200
producers
a Draw two pyramids of numbers, one for the grassland and one for the woodland.
b Why is the pyramid of numbers for the woodland such a funny shape?
Why does it differ from the pyramid at the top of this page?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
BUILDING PYRAMIDS OF BIOMASS
B41
To study
At each trophic level of a food chain or food web there is usually less mass of
organisms than at the previous level. We draw a pyramid of biomass to
show this. The length of each band shows the total dry mass of organisms at
that level in the food chain or food web.
Living things are mostly water. If you dry out the remains of living things you
are left with what we call dry mass. Dry mass is everything in a plant or
animal except the water. This has the stored energy which may be transferred
to the next level in the chain. This dry mass is mostly carbohydrates, proteins
and fats. We call it biomass because it has been made by living organisms.
tertiary consumer
secondary
consumer"
primary
consumer
n
"top carnivore
I I
carnivore
herbivore
producer
Ecologists studying the Eniwetok coral reef collected this data:
Organisms Mass of biomass per square metre in g/m2
Carnivores
10
Herbivores
130
Producers
700
Questions
1 Draw a pyramid of biomass for the Eniwetok coral reef. Use graph paper
and let the smallest squares represent 10 g dry mass per square metre.
(Hint: Rule a vertical line up the centre of the paper and draw the blocks
symmetrically on it.)
2 The Eniwetok coral reef data is in dry masses. Why record the data in this
form?
3 Why is it more useful to deal in biomass and not numbers of organisms?
4 Use the example of a woodland to explain why the biomass at the various
levels of a food chain alters during the year.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
PESTICIDES IN FOOD CHAINS
B42
In 1962 Rachel Carson's book Silent Spring created public alarm over the effects of pesticides. As
a result, more scientists began to study the effects of pesticides on living things.
Look at this data about the concentrations of the DDT in the body tissues of animals from an
estuary food web in Long Island USA. The data was collected in 1967 after years of spraying DDT
to kill mosquitoes.
Note: ppm means parts per million. 1 microgram (jig) is one-millionth of a gram.
So 1 |4,g in 1 g is the same as 1 ppm.
Organism
River water
Plankton
Silverside Minnow
Sheephead Minnow
Pickerel
Needlefish
Heron
Tern
Merganser
Cormorant
DDT / ppm
0.00005
0.04
0.23
0.94
1.33
2.07
3.57
3.91
22.8
26.4
Notes
pesticide runs off fields
small organisms which float in water,
they easily absorb pesticides
small fish eats plankton
small fish eats plankton
predatory fish
predatory fish
feeds on small animals
feeds on small animals
duck which eats fish
feeds on larger fish
Questions
1 Draw a food web for the animals in the estuary. Write the DDT concentration beside
each animal in the web.
2 How much more concentrated is DDT in plankton compared with the water?
3 Pick out from your web a food chain with four organisms. What can you deduce about
the concentration of DDT along a food chain?
4 A farmer sprays a field of cabbages with pesticide. Caterpillars with 0.1 microgram (|ig)
of pesticide in their bodies survive. During the next week some blue tits eat an average of
100 caterpillars each. In the next few weeks hawks each eat 100 blue tits. Assume that the
pesticide does not break down in the bodies of any of the animals.
a Copy and complete the table. (Remember, 1 Jig = one-millionth of a gram, so 1 jig in
1 g is the same as 1 ppm.)
Animal
Caterpillar
Blue tit
Hawk
Quantity of pesticide in
the body / |Xg
0.1
Body mass / g
1
10
100
cormorant
Concentration of
pesticide / parts per
million (ppm)
b A concentration of 100 ppm of the pesticide is fatal to hawks while 10 ppm affects their
chance of breeding successfully. Will the hawk population be affected?
5 Pesticides do not stay in the bodies of living things for ever. Suggest
some of the things that may happen to pesticides so that they disappear from
the environment.
© Nuffield Foundation 1996 R Carson, Silent Spring, Hamish Hamilton 1962

NUFFIELD BIOLOGY
B43
THE CARBON CYCLE (SIDE 1)
Todo
a Cut out the pictures on the diagram sheet.
b Cut out the names of the processes on the diagram sheet.
c Spread out the pictures on a sheet of paper. Arrange them in a way which gets over
the idea that there is a carbon cycle.
d Glue the pictures in place when you are happy with your arrangement.
e Draw in arrows between the pictures. Then stick the names of the processes beside
the arrows.
To study
Read 'Short circuit in the carbon cycle' below.
Short circuit in the carbon cycle
People short circuit the carbon cycle in two main ways. Burning fossil fuels releases carbon into the
atmosphere as carbon dioxide. Burning forests also releases carbon dioxide into the atmosphere and
destroys trees.
Scientists are concerned about the effect that this extra carbon dioxide will have on the Earth's climate
causing 'global warming'. Rays from the Sun have a short wavelength, with enough energy to penetrate
these 'greenhouse gases'. The rays are absorbed by the Earth, and re-radiated at a longer wavelength which
cannot pass outwards so easily. So the atmosphere is getting warmer.
Some people say that global warming is a good thing. Tomato production in commercial greenhouses is
better if there is more carbon dioxide in the air. They argue that extra growth in plants all over the world
might use up the extra carbon dioxide. But that can only happen when there is enough water (and other
nutrients) for growth. The increase in carbon dioxide levels may well reduce rainfall in many areas of the
world. We just don't know.
Since 1958, scientists have measured the amount of carbon dioxide in the atmosphere at the Mauna Loa
Observatory in Hawaii. They chose this site because it is a long way from people and industry - the
main sources of carbon dioxide. Their measurements show a gradual increase since these records began.
Questions
1 The article mentions two ways of 'short circuiting' the carbon cycle. What are they?
2 a What does the term 'short circuit' mean for electricity?
b Why does the author of the article apply the term 'short circuit' to human interference
with the carbon cycle?
3 a What evidence is there that human activity is having a steady, long term effect on the
worldwide carbon cycle?
b Why are people worried about the effects of human activity on the carbon cycle?
© in this format Nuffield Foundation 1996

NUFFIELD BIOLOGY
B43
THE CARBON CYCLE (SIDE 2)
Forms of carbon in the carbon cycle
Carbon in the bodies of
herbivores (as carbohydrates,
proteins, fats and other
chemicals)
Carbon in plant tissues (as
carbohydrates, proteins, fats
and otherchemicals)
Carbon in the remains of dead
plants, including wood
. 4x-
^
Carbon in the bodies of
decomposers (as
carbohydrates, proteins, fats
and other chemicals)
Carbon dioxide in the air
Carbon in the bodies of
carnivores (as carbohydrates,
proteins, fats and other
chemicals)
Carbon in the remains of dead
animals
Carbon in animal urine and
dung
Carbon in fossil fuels (coal,
natural gas and oil)
Processes in the carbon cycle
Photosynthesis
Fossilization (over millions of years) of the remains of
living things
Excretion of urine and dropping dung by animals
Herbivores feeding on plants
Death of plants
Respiration in animals
Carnivores feeding on other animals
Death of animals
Burning of coal and oil
Burning of plants (including wood)
Decomposers (soil bacteria and fungi) feeding on the remains
of dead plants and animals
Decomposers feeding on animal dung
Respiration in plants
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B44
THE NITROGEN CYCLE (SIDE 1)
Plants need nitrogen to grow. They use the nitrogen to make proteins. Nearly 80%
of the air is nitrogen, but plants cannot use it directly because nitrogen is a very
unreactive gas. So plants need soluble nitrogen compounds which they take in
through their roots. We use the term 'fixing nitrogen' for any process which takes
nitrogen gas from the air and turns it into soluble nitrogen compounds.
To do
Complete and label a nitrogen cycle on the diagram sheet. The notes and
sketches below will help you.
Chemicals in the nitrogen cycle
• Nitrogen in the air
• Nitrogen oxides in the air
• Ammonia in the soil
• Nitrates in the soil
• Proteins in plants
• Proteins in animals
nitrogen,
Organisms in the nitrogen cycle
• Bacteria in the root nodules of peas and beans which fix nitrogen
• Bacteria in the soil which fix nitrogen
• Decomposing bacteria in the soil which break down proteins to ammonia
• Bacteria in the soil which convert ammonia to nitrates
• Bacteria in the soil which turn nitrates back to nitrogen (denitrification)
• Plants
• Herbivores
ammonia, NH3
(N)
Processes in the nitrogen cycle
• Growing and making proteins
• Feeding on plants
• Excreting nitrogen compounds in urine
• Death and decomposition
• Bacteria fixing nitrogen to form nitrates
• Lightning flashes in thunderstorms which fix nitrogen and produce nitrates
in rain water
• Dentrification
• Nitrates washed out of soil into streams and aquifers (leaching)
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B44
THE NITROGEN CYCLE (SIDE 2)
r

NUFFIELD BIOLOGY
THE NITROGEN CYCLE GAME
B45
1 Denitrifying bacteria
in the soil release
nitrogen into air.
COLLECT TWO NITROGEN
TOKENS AS YOU PASS
2 Volcanoes release
new nitrogen into the
biosphere.
•£.
iu -; "B
3 Weathering of
igneous rocks releases
nitrogen ir£pj)iosphere.
V
21 High temperatures es
in car engines L
combine [~^ \
nitrogen and oxygen \
from the atmosphere. /
4 Industrial 'Haber
Process' makes
ammonia from
atmospheric nitrogen
and hydrogen.
!»*-:V:

NUFFIELD BIOLOGY
BODY DEFENCES
B46
Microbes are all around us. Some enter our mouths when we eat and drink. Some grow on our bodies.
It is not surprising that the body has some ways of defending itself.
To do
Sketch a body outline. Label your outline to show the body's defences against disease.
Choose from the phrases below.
• Unbroken, dry skin provides a
covering to prevent microbes getting in
• Mucus, a sticky liquid, traps
microbes
• Mucus in the windpipe traps
microbes. Coughing helps to move
the mucus and microbes out of the
windpipe
• Acid kills most microbes
• Poisons are removed by sickness
and diarrhoea
• The low pH of mucus in the
vagina protects against some
infections. The normal population of
bacteria in and around the vagina may
also give some protection
• Protection by the blinking reflex
and eyelashes. Microbes washed out
by a watery fluid
• Blood forms a protective cover or
scab
• White blood cells kill microbes in
time
• Body has little chance if needle is
not sterile
• No real defence here; care
especially in swimming pools
plaster
covering
cut
_
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
HOW DOES A THEORY BECOME AN
ACCEPTED FACT?
B47
In a novel by J. G. Farrell called The Siege of
Krishnapur, set in 1857, there are two doctors with
differing views of the cause of cholera. Dr
Dunstaple believed that it was caused by 'an
invisible cholera cloud' in the air. He did not
believe in germs. Dr McNab believed that treatment
must include chemicals to kill the germs and
sodium carbonate solution injected into the blood,
to restore the water and salts lost by diarrhoea. The
argument ended with Dr Dunstaple drinking the
watery faeces from a patient, to prove they were
harmless. He caught cholera and died.
Let us look at cholera and another disease called
puerperal fever. Today, we know that they are
caused by germs. But the germ theory of disease
look a long time to become accepted.
Early in the 19th century, it was very common for
women to die in childbirth. The illness was called
puerperal fever. In 1847, a young doctor in Vienna
called Ignaz Semmelweiss realized that the infection
was carried on the hands of doctors, who examined
the women after dissecting corpses. They hadn't
changed their clothes or washed their hands.
Semmelweiss reduced the chance of infection
dramatically, by insisting on rigorous cleanliness
and the use of antiseptics. Younger doctors
accepted his views. The older doctors didn't. They

NUFFIELD BIOLOGY_____________B48
GERMS AND YOU (SIDE 1)
To do
Decisions, decisions
a Form a group of six and pick one of the drawings on side 2 for this activity.
b Split into three pairs. In your pair discuss the point of view of one of the
three people shown in the picture on side 2; while the other pairs discuss the
point of view of the remaining people.
c Take a few minutes to jot down the key points that your person would make
in the situation shown.
d Try acting out the scene.
Types of diseases
Brainstorm
In a group make a list containing as many illnesses as you can think of. Think
up as many ideas as you can in a short time.
At first record all ideas without discussion. Get one person to write down all the
suggestions.
Decisions
Sort your list out under two headings.
Illnesses caused by microbes (germs)
Other illnesses
Questions
You recover from infectious diseases by making antibodies to attack them - a
different type of antibody for each type of bacterium or virus. You can be
prevented from catching the disease in the first place by being vaccinated. Use
library books to help you answer these questions.
1 What is a vaccine?
2 Why are vaccines so important?
3 How did vaccination get its name?
4 What do vaccines do in your body?
5 Which disease has been wiped out by vaccination?
6 Which diseases are the World Health Organization hoping to wipe out soon?
7 Why is it difficult to prepare a vaccine against cancer?
8 Why do people have to be vaccinated against flu every year?
9 Find out which vaccines you have had.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B48
GERMS AND YOU - DIAGRAM SHEET (SIDE 2)
I keep getting sore throats. What can
I do about it?
Should we get our baby immunized? What
about a whooping cough jab? We've heard
that sometimes it isn't a good idea?
These are only painkillers. The doctor said it
was a viral infection. Last time I had an
infection the doctor gave me penicillin.
I never take medicines. They re drugs you
know.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
ALCOHOL
B49
Question:
Answer:
What is the safe level of alcohol in your blood if you are driving?
None!
Don't be misled by the legal limit of 80 mg/100 ml. This is just the level at which a
conviction is automatic for everyone (because even a hardened drinker will be unsafe).
But if you are not used to drinking, a much lower alcohol level could lead to unsafe
driving, a conviction and death - either yours or a friend's.
The inputs are so variable that no-one can predict whether 2 pints of beer will put you
over the legal limit or not. And because alcohol affects your judgement, you may think
you are fit to drive when you are not.
INPUTS
OUTCOMES
Regular drinker or not
Body mass large or small
Metabolic rate high or low
Stomach full or empty
Liver healthy or damaged
Physical fitness/tiredness
Hangover
Accident
Heavy fine
Loss of licence for
at least two years
Possible imprisonment
for up to 10 years
Higher insurance
premiums
Loss of job, if it depends
on being a driver
Death
Even if all the inputs are in your favour, at twice the legal limit you are at
least 30 times more likely to have an accident.
Todo
In groups, try some of these questions.
a Discuss the inputs. How do you think they each affect the chance of an accident?
b Discuss the possible outcomes. How would each of these affect your life?
c A poster asks 'Who will be taking you home?' Underneath are pictures of a taxi,
a police car and an ambulance. Choose one of these and make up a short sketch
about a party, ending with that journey home. Would you go home with a driver
who had been drinking?
d Alcohol affects your judgement and self control. How do you think it increases
the chance of
• other accidents, • aggressive behaviour, • unintended sex?
e If you became an alcoholic, what effects might it have on
your family, your health, your friends, your career?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY_____________B50
STIMULUS AND RESPONSE (SIDE 1)
Carry out a selection of the activities suggested on this sheet. You will find more
detailed instructions on sides 2-4.
To do
Receptors in the skin
a Explore the sensitivity of your skin to touch, hot things and cold things (see side 2).
• Are all parts of your skin equally sensitive to touch?
• Are the skin receptors which detect hot things and cold things the same or different?
• How far apart must two points be for your skin to tell them apart? Do you get a
different answer for your fingertips compared with your wrist or the back of your hand?
• Can you suggest explanations for your findings?
Reflex responses
b Work in pairs to investigate reflexes (see side 3). One person is the subject and the
other the tester.
• Can the subject prevent a reflex response?
• Does the response change if the subject is concentrating on something else?
• Does the response change if the tester keeps repeating the stimulus?
Reaction times
c Measure your reaction time using the methods described on side 4.
• Do both methods give the same reaction time?
d Estimate the average speed of travel of the signal from eye to muscles via the brain.
• Can the subject's response improve with practice?
• Suggest some factors which might affect reaction times.
• Suggest an investigation into one or more of the factors. Show your plan to your
teacher. Try out your investigation if you have time.
Does learning improve response times?
e Working in a larger group investigate the effect of practice on response times (see
side 4).
• Does the speed of response improve with practice?
• Does it go on improving time after time?
To record
• Keep a note of your observations.
• Work in a group to prepare a short report or poster to tell the rest of the class about
your findings.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B50
STIMULUS AND RESPONSE (SIDE 2)
Receptors in the skin
You are going to investigate the sensitivity of your skin to touch, hot things
and cold things. You can compare the response of your skin in different parts
of your body - such as the palm and the back of your hand, your fingertips,
your arm and your leg.
To do
Use a pen and a plaster with holes in it to mark a
regular pattern of dots on the skin in each area you
are going to test. You can do the tests with and
without the plaster in place to see if this makes any
difference.
Touch
a The subject looks away.
b The tester touches a bristle against each of the dots
on the grid.
c The subject says 'yes' on feeling the touch of the bristle.
d The tester records the number of points which are sensitive.
cut here
sticky end of
plaster with
holes in it
Carry out
these tests
with care and
consideration
for the
subject.
Hot and cold
a Carry on as for touch but this time use the blunt end of a sterilized pin with its point pressed into a cork.
b Dip the pin-head into hot water each time before testing for sensitivity to hot things.
c Dip the pin-head into iced water each time before testing for sensitivity to cold things.
To do
One touch or t\vo?
a The tester uses a sterilized hairpin with the points a measured
distance apart. The subject looks away or puts on a blindfold.
b The tester presses the subject's skin with the hairpin, sometimes
using both points at the same time and sometimes just one point.
c The subject calls out 'one' or 'two' depending on the number of
points detected. The tester records the responses.
d The tester keeps doing this in a random way until it is clear
whether the subject can distinguish the two points.
e The tester bends the hairpin to change the distance between the
points and repeats the tests.
f The tester continues until it is clear how far apart the points must be for the
subject to be able to distinguish them.
single stimulus
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B50
STIMULUS AND RESPONSE (SIDE 3)
Testing reflex responses
To do
Knee-jerk reflex
a The subject sits with the right thigh crossed over
the left knee.
b The tester gives a sharp tap, just below the knee
cap, with the side of the hand.
Carry out
these tests
with care and
consideration
for the
subject.
Blink reflex
a The subject sits looking straight
ahead.
b The tester waves a hand in front of
the subject's eyes.
Pupil reflex
a Tester and subject sit facing each other in a room which is
dimly lit.
b The tester holds a torch about 10 cm to the side of the
subject's face.
c The tester switches the torch on and off at about 5-second
intervals and watches the pupils of the subject's eyes.
Look at the flow diagram. It shows the pathway of the nervous impulses causing a reflex action.
Stimulus
Receptor is
stimulated
impulses
along
sensory
nerve
Central
nervous
system
impulses
along
motor
nerve
Effect on
muscle
or gland
Response
Note that the central nervous system means the brain or spinal cord -
whichever part is nearest. So the blinking reflex will involve the brain, the
knee-jerk will involve the spinal cord.
Try to make a flow diagram for the reflex actions on this page. Try some
others too, e.g. secreting saliva when you smell some good food; burning
your hand on a hot plate and quickly pulling it away.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B50
STIMULUS AND RESPONSE (SIDE 4)
Reaction times
To do
Method 1 With a computer
a Load a program which allows you to
measure your response time.
b Follow the instructions on the screen. Hit
a key in response to the signal when it flashes
up on the display.
c Read off your average reaction time from
the screen after a number of trials.
Method 2 With a ruler
a Stick the paper strip you have been given to a ruler or strip of wood.
b Carry out the test as shown in the diagram.
c The tester releases the test strip without warning. The subject watches the
strip and tries to trap it with finger and thumb as quickly as possible.
d Read off the reaction time from the scale.
Does learning improve response times?
a Form a circle of about eight people. Face outwards.
b Place your left hand on the right shoulder of the person on your left.
c One person in the circle holds a stopwatch.
d At a signal from your teacher the person with the stopwatch squeezes the
shoulder of the person on their left - and at the same time starts timing.
e Each person responds to pressure on their right shoulder by squeezing the
shoulder of the person on their left.
f When the 'signal' gets back to the first person they stop the timer.
g Repeat this activity several times and note the times in order.
Test number
1
2
3 etc.
Time / s
Reaction time
Difference between one time and
the next / s
© Nuffield Foundation 1996

NUFFIELD BIOLOGY_____________B51
NERVES OR GLANDS? (SIDE 1)
That really got the
adrenaline flowing.
What have nerves and glands got to do with how we behave and how we
feel? Nerves and hormones help to organize all the activities in our bodies.
To do
The nervous system
a On the diagram sheet, label:
• parts of the body which respond to stimuli (receptors):
• light-sensitive cells in the eyes,
• cells which detect vibrations (sound) in the ears,
• receptors in the skin which detect pressure (touch), temperature changes,
and pain,
• receptors in muscles which detect changes in tension,
• a sensory nerve - which carries signals from a receptor to the central parts
of the nervous system,
• the spinal cord and the brain - which help to co-ordinate the response to a
stimulus,
• a motor nerve - which carries signals from the central nervous system to a
muscle,
• muscles - which contract to move parts of the body.
The hormone system
The hormone system is based on chemical messengers. Special glands, often
called 'trigger cells', release hormones into the blood.-A hormone circulates in
the blood plasma until it reaches the target cells in the organs on which it acts.
b Label these glands on the outline of the hormone system on the diagram
sheet:
• the pituitary gland at the base of the brain,
• the thyroid gland in the neck,
• the adrenal glands above the kidneys,
• the pancreas beside the small intestine,
• the reproductive glands (ovaries or testes).
c Write beside the name of each gland the hormone(s) it produces and the
effects of the hormone(s).
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B51
NERVES OR GLANDS? (SIDE 2)
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
HORMONES TO CONTROL
BLOOD GLUCOSE
B52
(SIDE 1)
In this activity you are going to work out an explanation for the importance of
the hormone insulin; the symptoms (effects) of diabetes, and how to treat it.
To do
Select information from the grid below and drawings from the diagram sheet
to write illustrated explanations of the control of glucose levels in the blood
and the disease diabetes. Start with the information in the white boxes. Add
the information in the shaded boxes if you can.
Cover these points:
a how negative feedback in a healthy body keeps the blood glucose
concentration within the normal range (homeostasis),
b the symptoms of diabetes: thirst, steady weight loss, glucose in the urine,
breath with a fruity smell, leading eventually to unconsciousness,
c how diabetics achieve control of their disease.
Enzymes in the gut digest
starch from our food into
glucose.
Insulin encourages liver cells
to store glucose by
converting it into glycogen.
Respiration tr^nifes energy
to body processes by turning
glucose and oxygen into
carbon dioxide and water.
The pancreas of diabetics
cannot make enough insulin.
Without the hormone insulin
it is impossible for glucose
molecules to get across cell
membranes.
The glucose concentration in
the blood rises after a meal.
When blood sugar levels are
normal there is no glucose in
urine.
In a healthy person there is
always a minimum low level
of insulin in the blood.
Production of insulin
increases when the glucose
level in the blood rises.
All cells in the body need
glucose for respiration.
Untreated diabetics become
increasingly weak and may
pass into a coma and die.
When blood sugar levels are
too high glucose appears in
the urine.
When insulin has done its
job it is broken down.
The production of urine
increases when blood sugar
levels are so high that
glucose passes from blood to
urine in the kidneys.
An untreated diabetic has
high concentrations of
glucose in the blood.
Clusters of cells in the
pancreas produce the
hormone insulin and release
it directly into the blood.
Diabetics steadily lose
weight if they do not have
enough insulin.
Diabetics give themselves
insulin injections several
times a day - usually shortly
before meals.
Production of insulin by the
pancreas falls as the glucose
concentration in the blood
falls.
||S||I||f|^|||)gel|||
"fulglll^
Without insulin, cells
(including muscle, liver, and
brain cells) cannot get the
glucose they need.
After digestion, small
glucose molecules pass from
the gut into the blood.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
HORMONES TO CONTROL
BLOOD GLUCOSE
B52
(SIDE 2)
digested
food
blood
vessel
pancreas
body cell
_pancreas
insulin
^glucose
molecule
blood
kidney
urine
1 in this format Nuffield Foundation 1996 Based on Insulin-dependendent diabetes, Novo-Nordisk Pharmaceuticals Ltd,
Crawley, West Sussex

NUFFIELD BIOLOGY
HORMONES AND CYCLES
B53
During their reproductive lifetime (from puberty to menopause) women have periods.
The series of changes from one period to the next is called the menstrual cycle. Four
hormones control the menstrual cycle. The hormones are:
• FSH and LH from the pituitary gland, and
• oestrogen and progesterone from the ovaries.
To do
a Cut out the eight drawings and the eight captions on this sheet. Match the captions
with the drawings. Then arrange the drawings and captions to describe the menstrual
cycle. Finally stick down the drawings and captions on a sheet of paper.
b Use the chart from a to explain how a pill containing oestrogen and progesterone
can act as a contraceptive.
c Use the chart from a to suggest a way of treating an infertile woman who cannot
have children because her ovaries do not release eggs.
Key:
FSH
LH
oestrogen
progesterone
where the
hormone
comes from
where the
hormone
acts
'yellow
body' in
ovary
The 'yellow body' releases
progesterone into the
bloodstream. Progesterone
prevents the pituitary gland
releasing either LH or FSH.
If the ripe ovum in the
oviduct is not fertilized
within a few days, the
'yellow body' stops making
progesterone and breaks up.
As the level of progesterone
falls, the thickened lining of
the uterus breaks up and
menstruation (bleeding or
a 'period') occurs.
As the ovum grows, the
ovary begins to release
oestrogen into the
bloodstream.
The sudden flow of LH in the
blood causes the release of
the ripe ovum from the ovary
into the nearby oviduct. This
is ovulation. In the ovary,
the small mass of cells
which held the ovum begins
to develop into a 'yellow
body' (corpus luteum).
The rising level of oestrogen
in the blood causes two
things to happen:
• less FSH is released - so
no more ova will develop,
• the lining of the uterus
thickens to be ready to
receive the fertilized ovum.
The menstrual cycle begins
as the pituitary gland starts
releasing FSH into the
bloodstream.
The ovum continues to
ripen, and the increasing
amount of oestrogen
eventually triggers the release
of LH by the pituitary gland.
The increasing amount of
FSH in the blood stimulates
the growth of an ovum in
one of the ovaries.
© in this format Nuffield Foundation 1996
Diagrams based on Natural History Museum, Human biology: an exhibition of ourselves, Cambridge University Press, 1981

NUFFIELD BIOLOGY
TROPISMS IN SHOOTS
B54
When a seed germinates its root grows down into the soil while its shoot
grows up into the air. How does the shoot know which way to go as it
emerges from the seed?
In this activity you are going to study the behaviour of shoots. You will start
with seedlings which have grown until they have two seed leaves
(cotyledons) supported by a hypocotyl (the stem below the cotyledons).
To discuss
• Read through the instructions. What question might you be able to answer
about plant growth when you have completed this investigation?
• What factors might affect the growth of the cut end of the seedling?
• Predict how the cut end will respond. Will it grow upwards or downwards
or straight along?
To do
a Cut a seedling at soil level using sharp scissors.
b Take a black film can and draw a line on the barrel and
lid with a marker pen. This will allow you to line up the lid
when you put it on the barrel.
c Cut a piece of filter paper so that it just fits inside the lid
of the can.
d Put the filter paper into the lid and dampen it.
e Mount the barrel of the can on its side on the bench
using Blu-tack, with the marker-pen line uppermost.
f Attach the seedling to the filter paper inside the lid by its
cotyledons. The water will make it stick.
g Fit the lid on to the barrel of the can. Line up the mark
on the lid with the mark on the barrel.
h Take off the lid and look at the hypocotyl every 15
minutes.
i Use the marks to make sure that you replace the lid in
exactly the same place each time.
film can lid
disc of filter paper
Take care
when using
sharp
instruments.
hypocotyl
cotyledons
hypocotyl
cut here
black film
canister
film can
cotyledons
marker
pen
line
filter paper
can lid
To record
• Note what you see each time you look at the hypocotyl.
• Were the results as you predicted?
• Which factor or factors seem to be affecting the way the hypocotyl grows?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B55
TROPISMS AND PLANT HORMONES (SIDE 1)
The seedlings in the drawing are on
a window sill. The shoots are
growing towards the light. The
technical term for a 'growingtowards-the-light
tendency' is
positive phototropism. Why
does it happen? The diagrams on
side 2 describe some investigations
which help to answer this question.
Your task is to interpret the results.
Questions
Investigation I
1 What is the question that this investigation is designed to answer?
2 What is the response and where in the seedling does it take place?
3 Suggest a hypothesis to explain what happens between the stimulus and the
response.
Investigation 2
1 What is the question that this investigation is designed to answer?
2 What do the results tell you about the effect of the shoot tip on the cells just
below it?
3 Where in the shoot do cells divide to make more cells? Where do the cells
just grow bigger?
Investigation 3
1 What is the question that this investigation is designed to answer?
2 Why use a piece of gel (gelatin or agar jelly)?
3 What does the investigation suggest about the nature of the signal passing
from the shoot tip to the cells below?
Investigations 4 and 5
1 What are the questions that these investigations are designed to answer?
2 Explain the design of the two investigations.
3 Suggest an explanation for phototropism based on the results.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B55
TROPISMS AND PLANT HORMONES (SIDE 2)
The seedlings in these experiments are
cereals, such as barley. The shoots look
different from cress seedlings. They seem
to have no leaves. In fact the shoots,
called coleoptiles, are closed tubes with
the long narrow cereal leaves inside.
Investigation 1
forceps
At the start
-aluminium foil j:ap
"\\gM~
Later
light
cover tip of shoot with foil
cap and light it from the side
Investigation 2
At the start
Later
leave the shoot uncovered
and light it from the side
both have grown a bit longer
tip of shoot cut off
Growth
stops
Investigation 3
tip cutoff,
then put
back
Growth
continues
1 Tip of shoot cut-off 2 Growth
and placed on agar stops
gel
3 Agar gel 4 Growth
placed on starts
cut end of again
shoot
Investigation 4
At the start
Later
Investigation 5
shoot
cut made
here
shoot
left on agar
jelly for 1
hour
central
of agar jelly
shoot-
freshly cut shoot-—-"
fresh piece
of agar jelly
freshly cut shoot
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B56
RIGHTS AND WRONGS OF USING HORMONES
You will need to do some research in preparation for this discussion activity.
To do
a On your own
Each statement in the grid describes a use of hormones. For each statement decide
whether you agree, disagree or are not sure whether it is right to use hormones in
the way described. Try to have a well-thought-out reason to support each decision.
b In a group
• Compare your responses to each statement.
• Where you disagree, discuss the statements. Can you reach agreement?
• Compare the reasons for your decisions.
c All groups together
• Report your decisions to other groups.
• Discuss similarities and differences in your points of view.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Use of hormones Agree Not sure Disagree
Using hormone creams to treat skin problems
Using oestrogen and progesterone in contraceptive pills
Injecting BST into cows to increase milk production
Taking steroids to improve athletic performance
Injecting insulin as a treatment for diabetes
Using hormone rooting powders when taking cuttings of plants
Testing new hormone treatments on animals
Using hormones to stimulate ovulation as a treatment for infertility
Using hormones as selective weedkillers on lawns and playing fields
Implanting hormone pellets into beef cattle to increase meat production
Hormone replacement therapy (HRT) during and after the menopause
Spraying plant hormones on wheat to control the number of ears of corn
Taking contraceptive hormones to relieve period pains
Treating someone with hormones to bring about a sex change
Spraying fruits with hormones to control their growth and the time they
ripen
Using hormones to stimulate the uterus of a woman who has passed the
menopause, so that she can become a surrogate mother
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B57
KEEPING A STEADY STATE (SIDE 1)
Tropical fish need looking after. The water must be warm, but not too hot. Fish need
oxygen, food and ways to get rid of waste products. In a well-run tank everything stays
in a 'steady state' and the fish thrive. Here is a diagram to show the parts that help to
keep the water at a steady temperature.
water
filter
combined
thermostat
and
heater
air bubbler
In some ways the cells in your body are rather like fish in a tropical tank. They do not
swim about but they live in a watery fluid which brings to them everything they need to
survive and takes away all wastes.
Here is a flow diagram to show how you keep the right amount of water in your blood.
Blood needs
more water
Sensory
cells in
brain
Hormone
released
from brain
Hormone
carried
in blood
Target cells
in kidney
receive the
information
Kidney reabsorbs more
water from the filtrate
back into the blood, so
less is lost in the urine
Biologists have a special word for 'keeping a steady state' - they call it homeostasis.
Homeostasis means 'staying the same'.
Questions
1 When you take strenuous exercise, extra carbon dioxide builds up in your
bloodstream. Your body makes adjustments. Draw a flow diagram to show how the
concentration of carbon dioxide is brought back to normal.
2 Make up another flow diagram to show how you keep your body's core temperature at
about 37 °C, even during strenuous exercise which releases a large amount of heat.
If you have time
3 Astronauts need 'life support systems' which control the conditions in which they live. Use
encyclopaedias to find out how people can survive in space. How might a steady state be achieved in a
space suit?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B57
KEEPING A STEADY STATE (SIDE 2)
The table shows results of an investigation to compare the rate of sweating by a
person at various skin temperatures when resting and when jogging.
Skin
temperature / °C
31.5
32.0
33.0
34.5
35.0
36.0
Questions
Relative rate of sweating
when resting
2
2
2
4
5
8
when jogging
3
5
8
17
20
34
4 Display the results in the table in a way which will allow you to describe the
relationship between the relative rate of sweating and skin temperature when resting.
5 Describe the relationship between the relative rate of sweating and skin temperature
when resting.
6 Compare the effects of jogging and resting on sweating at different temperatures.
7 How does sweating help to cool the skin?
This graph shows the results of an experiment to investigate temperature control in the
human body. In this experiment a man stayed in a room kept at a steady 45 °C. The
scientists logged his internal body temperature, skin temperature and rate of sweating.
After 25 minutes in the room the subject drank a large quantity of ice-cold water.
o 38.0 -i
c
£ 37.8
0.
37.4
body temperature (internal)
rate of sweating
r-7 -rx
5 .«
37.2
37.0-
skin temperature
36.8 4—
-2 •*-
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85
Time (minutes)
8 Why is it important for the human body to stay close to its normal temperature?
9 How can you account for the pattern of the results in the first 25 minutes after the
man went into the room?
10 Use the information on the graph to describe and explain the effects of
drinking a large amount of ice-cold water.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B58
WHAT DOES DIALYSIS DO TO
BLOOD? - PART 1 (SIDE 1)
In this experiment you are going to find out how a dialysis machine imitates the action of the
kidney. The 'blood' you use is not real blood but it will behave in the same way in your tests.
You are going to use Visking tubing. Visking tubing acts as a molecular sieve. It lets through
small molecules but not big ones. (It is semi-permeable.) Visking tubing is like the membranes
used in dialysis machines.
To do
a Moisten a 20-cm length of Visking tubing in a beaker
of water. Rub it between your fingers to open it up.
b Tie a knot in one end of the tubing.
c Fit the cut end of a syringe into the open end of the
Visking tubing, and fix it with an elastic band.
d Place about 10 ml 'blood' inside the tubing.
e Rinse the outside of the tubing with distilled water.
f Place the tubing in a boiling-tube of distilled water at
37 °C (the dialysis fluid). Keep this water at 37 °C by
standing the boiling-tube in a water bath.
thermometer
elastic
band
beaker
of warm
water
g At intervals of about 30 seconds gently stir the water by raising and lowering the Visking tubing.
After about 5 minutes test the water in the beaker in the following ways. Avoid getting any silver
nitrate solution on your skin. If you do, tell your teacher and wash your skin carefully with lots of
water.
• Dip in a glucose test strip and check the colour, or do a Benedict's test.
• Dip in a protein test strip and check the colour, or do a Biuret test.
• Pour a few mililitres of water from the boiling-tube into a test-tube. Add a few drops of silver nitrate
solution. The formation of a white precipitate (a white cloudy solid) tells you there is salt in the water.
• Note whether there is any red colour in the water in the beaker.
• After another 5 minutes repeat each of these tests.
To record
Wear gloves silver nitrate
Copy the table below and record your results.
If you have a colour chart for the test strips for glucose and protein, you will be able to write down their
concentrations in water.
Dialysis fluid after 5 minutes
Dialysis fluid after 10 minutes
Glucose Salt Protein Red colour
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B58
WHAT DOES DIALYSIS DO TO
BLOOD? - PART 2 (SIDE 2)
One of the main jobs of the kidneys is to control the amount of water in the blood. Kidneys
also control the concentrations of dissolved salts and get rid of wastes such as urea that are
harmful if they build up in the body.
Questions
Answer these questions with the help of your results from part 1.
1 Which substances get through the dialysis (Visking) tubing?
2 Which substances do not get through dialysis tubing?
3 Copy out the sentences below, leaving out the incorrect words, to give a summary of
your results.
• Substances with large/small particles (such as sugar and salt) can/cannot get through
dialysis tubing.
• Substances with large/small particles (such as protein) and cells (such as red blood
cells) can/cannot get out of the blood by passing through dialysis tubing.
4 Urea is a waste product produced as the liver breaks down amino acids. The urea then
travels in the blood to the kidneys to be excreted. The molecules of urea are small. What
would have happened to any urea dissolved in the 'blood' used in your experiment?
Would it have remained in the 'blood' or passed through into the dialysis fluid?
Read about dialysis in a textbook. Look carefully at these drawings of blood
going through the kidney and blood going through a dialysis machine.
5 How does the blood
coming out of a kidney or
dialysis machine differ from
the incoming blood? What
has been filtered out?
6 What substances are in
urine?
7 Compare the dialysis
fluid going down the
waste pipe with urine.
8 What happens to glucose
in a kidney?
blood-protein,
blood cells, glucose,
water, salt
DIALYSIS
MACHINE
dialysis
fluid
containing
glucose
blood-protein,
blood cells, glucose,
water, salt, urea
to waste pipefluid
containing
glucose, urea
some salt and
water
blood-protein,
blood cells, glucose,
salt, water, urea
KIDNEY
ureter
artery
bladder
9 Dialysis fluid contains glucose. The glucose concentration is the same in the fluid as in
blood. Why is this necessary? (Clue - look back to your results in part 1 of this activity.)
10 People on dialysis, a have a low protein diet; b have a low salt diet; c restrict their
fluid intake. Can you suggest the reason for each of these?
blood-protein,
blood cells, glucose,
salt and some water
urine to waste
pipe-water, urea,
some salt
vein
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
A MODEL OF MITOSIS
B59
To do
a Spread a piece of cloth on a bench. This is the outline of your 'cell'. Lay a long piece of
string on the cloth so that it forms a circle. This is the membrane of the 'nucleus'. Now put
three different coloured pieces of wool inside the 'nucleus' at random.
These pieces of wool are the model chromosomes. Chromosomes carry the instructions
about an organism which determine its appearance and body chemistry. Before the cell
divides, the chromosomes reproduce themselves exactly. This process is called
replication.
b 'Replicate' your model 'chromosomes' by putting three more pieces of wool alongside
the pieces that are already in the model 'nucleus'. Make sure that you match up the colours
and lengths. Join the pieces of wool with two pieces of plasticine or Blu-tack as shown.
2 pieces of Plasticine, touching but
not tightly pressed together
c Remove the 'nuclear membrane' in your model and line up the chromosomes along the
centre of the cell.
d Tie a long piece of thread round the centre of each chromosome and then set up the
threads as shown.
pull slowly
sticky tape
—*• pull slowly
thread
e Pull the threads slowly at the same time as your partner is pulling in the opposite
direction. Make sure that you start pulling at the same time.
1 How do the chromosomes behave as they are pulled?
Once the chromosomes have separated, a nuclear membrane reforms round each set and the
cell divides in the middle.
f Now go back to step a and repeat the same process for each of your new cells so that you
have four cells.
2 How is the number and type of each chromosome kept the same in each cell?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
CELLS DIVIDING
B60
To see what happens to the nuclei when cells divide you need to look at tissue
where the cells are dividing rapidly. A good choice is just behind the tip of a root.
To do
a Cut three 2-mm sections from the tip of
the root, such as from a germinating pea.
b Add the sections to a test-tube containing
0.5 cm3 dilute hydrochloric acid.
c Label your tube. Stand it in a water bath
at 60 °C for 5 minutes. This will help to
break down the cell walls.
d Remove the root sections from the acid.
Wash them on a watch glass with clean
water.
e Put each section on a different slide
labelled 1, 2, 3 to show where the section
was taken. Add a drop of stain.
f Break up the section with a needle.
g Cover with a cover slip. Then gently
squash the material with the slide
sandwiched between two layers of a paper
towel.
h Tap the cover slip lightly with the handle
of the needle to release the material.
i Examine the material through a
microscope.
place in
hydrochloric
acid and keep
in water bath
Wash your
hands after
3 handling plant
2 Section material
1
To record
Draw diagrams to show what you see in the root cells. Start with
region 3. If possible, draw a few typical cells from each region.
squash gently
Questions
1 Where are the chromosomes in a cell?
2 How does this process of nuclear division make sure that each cell in the body
has the same number of chromosomes in its nucleus?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
A FLICK BOOK TO SHOW MITOSIS
B61
In the time it has taken you to read this sentence, your body has made thousands of new cells. Between one
meal and the next, the cells lining the whole of your digestive system have been replaced. Every second,
one hundred million new red blood cells are made by the average adult! The next time your science teacher
accuses you of being lazy, you might reflect on what an effort this has all been.
Nuclei divide by two kinds of division called meiosis and mitosis. Meiosis occurs only in 'germ cells'
the cells which produce eggs and sperms (or ovules and pollen grains in plants). Mitosis occurs in 'body
cells' and this worksheet is about this kind of division.
The instructions to make and operate cells are found inside the nucleus. Before a cell divides, these
instructions are copied. The instructions are carried in structures called chromosomes. When cells divide,
the chromosomes become visible, and the two identical copies move to opposite ends of the cell. Two
daughter cells, each with a nucleus carrying its own set of instructions, are eventually produced. Although
scientists have names for different stages in nuclear division, it is actually a continuous process as your
'flicker book' will show.
To do
Cut out the diagrams below and staple them together to make a 'flicker book'. It will be easier if each sheet
is moved slightly to the right of the one above (so that sheet 12 is about 3 mm to the right of sheet 1).
Alternatively you could glue them on the bottom right hand corners of the pages in your notebook. Flick the
pages of the book to produce an animation of nuclear division.
cut
cut
10 11 12
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B62
DNA, GENES AND PROTEIN SYNTHESIS
(SIDE 1)
DNA is a giant molecule which is made from four different types of unit. Each type of unit is distinguished
by one of a sequence of four chemicals called bases. The four bases are labelled with their initials in the
diagram below.
base
this part goes to make
the 'backbone' of DNA
A = adenine T = thymine G = guanine C = cytosine
In DNA, the units are joined together to form a double-stranded helix like a twisted ladder with the bases
pointing inwards and paired together so that weak bonds are formed between G and C or A and T.
'backbone'
two strands in
a double helix
Questions
1 The units are joined together by condensation reactions to make the 'backbone' of the DNA. What is
meant by a condensation reaction? (Look this up in a chemistry textbook if you are not certain.)
2 Which bonds are most likely to break when the DNA strands separate during the replication process?
There are many thousands of pairs of bases along a DNA molecule and these are arranged in an irregular
order (see the diagram of DNA above). Genes are particular stretches of a DNA strand and there are
hundreds of different genes along a strand of DNA.
3 What would be the result, if the wrong base was put into the DNA molecule during replication?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B62
DNA, GENES AND PROTEIN SYNTHESIS
(SIDE 2)
How are proteins made?
The order of the units along the strand of DNA controls the synthesis of proteins in the cell. For this part of
the activity you will need the drawings on side 3.
a Cut out the rectangle which shows part of a DNA molecule which has unwound.
b Cut out the units with their 'pieces of backbone' and place them so they pair up with the 'opposite shape'
of the units in the DNA strand. The position of the first one is shown by a dotted line.
c When all the units have been paired up, join them up by their 'backbone' with sticky tape taking care that
they remain in the correct order. Do not stick them down on the page yet.
The molecule you have just made is called messenger RNA (mRNA). It is not DNA because it is a single
strand and it does not contain the base (T). In place of it, it has another base, (U). Messenger RNA is a
kind of opposite image to the DNA strand; it is said to be complementary to it. Proteins are made in the
cytoplasm of the cell so the mRNA moves from the nucleus through special pores in the nuclear membrane.
d Move the strand of mRNA you have made away from the DNA, and glue it into your book.
Amino acids, the building blocks which make up proteins, are brought together at certain places in the
cytoplasm called ribosomes.
The mRNA is essential for protein synthesis because it contains a code for particular amino acids. This code
consists of groups of three units and is called a triplet code. Particular amino acids are coded by particular
triplets of units.
codes for
amino acid
A
amino acid
B
A,B,C and D are different amino acids.
Their proper names have not been given.
There are 20 different types of amino
acids in proteins.
messenger RNA
The code is transferred from the mRNA using special molecules called tRNA (transfer RNA) molecules.
Different amino acids are carried by different tRNA molecules.
e Cut out the four tRNA molecules which are carrying their particular amino acids.
f Fit the tRNA molecules carrying the amino acids onto the mRNA strand starting at one end. You should
find only one way that you can fit them in exactly.
g Join the amino acids together with sticky tape then cut the dotted lines with scissors. You have now
made your 'protein chain'.
h Work out the original order of three units in the DNA which is responsible for coding for the amino acid
called glycine. You can do this by working backwards and seeing which nucleotides 'fit together'.
Individual proteins are coded by a particular order of units along the DNA strand and a particular number of
units in a particular order is a gene. The sequence is different for different proteins. One strand of DNA can
code for hundreds of proteins.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B62
DNA, GENES AND PROTEIN SYNTHESIS
(SIDE 3)
parts of an unwound DNA strand
Bases to make the mRNA strand
amino acid
lysine
amino acid
serine
transfer RNA for the
amino acid lysine
transfer RNA for the
amino acid serine
amino acid
glycine
amino acid
leucine
transfer RNA for the
amino acid glycine
transfer RNA for the
amino acid leucine
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B63
CHROMOSOMES IN SEX CELLS (SIDE 1)
To do
a Label the diagram on this sheet to show what happens during and after
fertilization. Use these words: ovary, egg (female sex cell), sperm (male sex
cell), fertilization, ball of cells, uterus, placenta and embryo forming in uterus.
b The upper diagram on the diagram sheet shows what happens when body
cells divide to make sex cells (gametes). The diagrams are in the right order.
Label the diagrams with these words or phrases (which are not in the right
order).
Each chromosome forms an
identical copy. Similar
chromosomes come together.
The two copies of each
chromosome split away from
each other and move apart as the
cell begins to divide into four
parts.
The chromosome pairs separate
and move apart as the cell begins
to split into two.
Chromosomes thicken and
become visible when the cell is
about to divide.
The nuclear membrane
disappears. The pairs of
chromosomes arrange themselves
in the middle of the cell.
Four nuclei are made, each
surrounded by a membrane. The
cell splits to produce four sex
cells.
Questions
1 Make a table to show the differences between
nuclear division making body cells, and nuclear
division making sex cells.
2 Complete the lower diagram on the diagram
sheet by writing the number of chromosomes into
the outline of each type of cell.
3 Human body cells contain 46 chromosomes.
How does this number stay the same from one
generation to the next? What stops the number
doubling each time a sperm fertilizes an egg?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B63
CHROMOSOMES IN SEX CELLS (SIDE 2)
Father
cell in the
testis
'dividing to
form sperm
o
dividing
'toformeggs\
O \
M
N
fertilization
' fertilized cell
(zygote)
ball of dividing
cells (embryo)
© in this format Nuffield Foundation 1996
Diagram based on drawing of stages in fertilization modified from Mackean, D G , GCSE Biology, John Murray, 1986

NUFFIELD BIOLOGY
B64
VARIATION IN PEOPLE (SIDE 1)
'Variety's the very spice of life, That gives it all its flavour.'
Why do people vary? How much do they inherit from their parents?
How much is due to the conditions in which they live and grow?
Continuous variation
Height is an example. As the graph shows, most pupils in their first year of
secondary school vary in height between 136 cm and 171 cm. They could be any
height in between, but the most common height is near the middle of the range.
Discontinuous variation
Nose shape is an example. Nose shapes fall into a small number of distinct
types.
Here are some features of people to observe or measure and record.
arm span (cm)
height (m)
leg length (cm)
mass (kg)
length of stride (cm)
handedness
shape of thumb
nose shape
reach (cm)
shape of ear lobes
ear lobe
'no lobe ^-/ \_J free
direct join halfway join indirect join
To do
Three examples of discontinuous variation
straight
thumb
fingerprints
tongue rolling
freckles
hair colour
hair texture
hitch-hiker's
thumb
a Think of a question about human variation to investigate.
>32
.2-30
228
£ 26
I 24
^ 22
20
18
16
14
12
10
8
6
4
2
rr>n
COOO
P-3 co *
tongue not rolled
l«a-CDOOOCM1- LO u~> en co coco to i~~
Height (cm)
Continuous variation in the height of 200
first-year pupils in a secondary school
b Carry out a survey - starting with others in your class perhaps - to investigate your question
To record
• Make a note of your findings.
• If possible, use a computer to record, display and analyse your data. (See side 2 of this activity.)
• Make a list of features which show continuous variation.
• Make another list of features which show discontinuous variation.
To discuss
• Which of the listed features are inherited?
• Which features are affected by environment?
• Which features are affected by both inheritance and environment?
tongue rolled
• Do you think the features in this last group would produce a graph similar to the one at the top of this
page - showing most people near the average value, and few people at the two extremes?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B64
VARIATION IN PEOPLE (SIDE 2)
Putting data into a computer
To do
When everyone in your class has entered their records, use the computer
program to study the data. Steps a, b and c will help you to get used to using
the software.
a Examine the data for the heights (or masses) of people in the sample. What
is:
• the smallest value,
• the largest value,
• the range,
• the commonest value (the mode),
• the average value (the mean)?
b Display and print out a chart to show the heights of the people in the
sample.
c Are taller people heavier? Display and print out a scattergram plotting the
heights and masses of the people in the sample.
d Think of your own questions about people and variation. Use the data file
to answer your questions.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
VARIATION IN IVY LEAVES
B65
The same ivy plant may grow along the ground and up the
trunk of a tree. This means that conditions may vary for
different parts of the same plant. How does this affect ivy
leaves?
To design
You can compare leaves by measuring their width and the
length of their petioles (leaf stalks).
Design an investigation to explore how environmental factors affect the growth
of ivy leaves.
• What are the variables which might affect the growth of ivy leaves?
• What question are you hoping to answer?
• Can you predict the answer to your question?
• Where will you collect your ivy leaves?
• How many leaves will you need to collect and measure to get reliable results?
• How will you decide which leaves to pick?
• What will you measure?
Wash your hands after handling plant material.
To record
• How will you record your data?
• How will you display your data so that you can see any patterns in the results?
To interpret
• What patterns can you see from your measurements?
• Do your results help to answer the question you set out to investigate?
• Can you explain your findings, helped by what you know about growth?
• Do your results suggest that differences in the environment influence the
growth of ivy leaves?
Where will the
ivy come
from? Check
your plan with
your teacher
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B66
GENERATIONS OF TOMATO PLANTS (SIDE 1)
In this activity you are going to study colour in three generations of seedlings.
To do
a Look at the two sets of tomato
plants. These are seedlings of the parent
plants in this activity. Colour in these
two diagrams to show the colours of the
young plants.
b You are about to see a first
generation of offspring (Fi) from the
parent plants. The seeds formed when
flowers from a tomato plant of one
colour were fertilized with pollen from
the plant of the other colour. Predict the
colour of the seedling leaves. Colour
the TI prediction' diagram to show
what you expect.
F, prediction
c Now look at the pot with the FI
seedlings. Colour the TI actual'
diagram to show what the seedlings
look like.
Ft actual
d The next generation of plants (F2)
has grown from seed formed when FI
flowers were fertilized with their own
pollen. Colour the 'F2 prediction'
diagram to show what you expect.
e Now look at the pot with the F2
seedlings. Colour the 'F2 actual'
diagram to show what the seedlings
look like.
F2 actual
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B66
GENERATIONS OF TOMATO PLANTS (SIDE 2)
To study
The theory of genes can explain your observations with tomato seedlings.
Genes carry the instructions from one generation to the next. In the simplest
examples genes control characters such as leaf colour, plant height, seed shape
and so on.
Body cells contain chromosomes in pairs. One of each pair comes from the
female parent, the other from the male. A chromosome consists of many genes
along its length like beads on a string. Every gene appears twice - once on
each of the chromosomes in a pair.
In the green seedlings both forms
of the gene say 'be green'
gene controlling the
colour of seedling leaves
parts of two equivalent
chromosomes (one
inherited from the male
parent and the other
from the female parent)
There are alternative forms of the same
gene. We call the different forms alleles.
In this activity one form of the gene for leaf
colour says 'be green'. The other form says
'be yellow'.
Geneticists use letters of the alphabet to
represent alleles. Here we can use G for the
form of the gene which says 'be green' and
Y for 'be yellow'.
Todo
Complete this diagram to explain your
observations with tomato seedlings. State
the colours of the leaves in each generation:
green, yellow or yellow-green. Use the
symbols G and Y to show the forms of the
leaf-colour gene in the sex cells and body
cells of each generation.
First cross
alleles in parent
body cells
alleles in
sex cells
alleles in cells of
first-generation
plants (F,)
Second cross
F 1 plants used
as parents
alleles in
sex cells
alleles in cells
of secondgeneration
plant
G allele: cotyledons (seed leaves) are green
Yallele: cotyledons (seed leaves) are yellow
green leaves
, leaves
yellow leaves
. leaves , leaves
leaves ....... leaves ....... leaves ....... leaves
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
MAKING AN IDENTIFICATION KEY
B67
This is an identification key for five different lichens which grow on rocks or trees.
very pale green
lichen
bright orange
lichen
olive green
lichen
pale
grey-green
lichen
pale
yellow-green
lichen
1 The lichens grow on tree bark..............................Go to 2
The lichens grow on rocks..................................Go to 4
2 They grow flat against the surface.........................Parme//a subrudecta
They have branches which grow away
from the surface..............................................Go to 3
3 They have long dangling branches........................ Usnea
They have short branches................... ...............Evernia
4 They are bright yellow...................... ...............Xanthoria
To do
They are pale grey-green............. .....................Parmelia saxatilis
Imagine two new lichens have been found. They have no names and are called X and Y.
X is a bright orange lichen which has branches that grow away from the rock surface.
Y is a pale grey-green lichen which has branches that grow away from the rock surface.
• How would you change the key to fit in X and Y?
To discuss
• Work in a group of four.
• On a sheet of paper the first person writes the name of an organism and a
very short description of it.
• Fold the paper down to hide what you have written and give the paper to
someone else in the group.
• When everyone has written a description, open the paper out and use the
descriptions to make a key to identify the organisms people have chosen.
© in this format Nuffield Foundation 1996
Adapted from 1995 Key Stage 3 Science Test Papers. Crown copyright. Reproduced with the permission of the Controller of HMSO.

NUFFIELD BIOLOGY_____________B68
BREEDING WITH BEADS (SIDE 1)
To a scientist the word model means a simplified way of explaining how something is
arranged or how it functions. In this worksheet you are going to use beads to represent
the gametes, alleles and genotypes involved in breeding investigations. This model can
help you to find out whether you are justified in making the assumptions that you use in
theoretical genetics.
For each investigation you will need poppet beads of two colours, and you will use 200
of each colour.
Investigation 1:
To demonstrate that fertilization is a random process
Todo
a Let a bead of one colour, red for example, represent a sperm and a bead of another
colour, such as yellow, an egg. Put 200 red beads in one container - the 'male' container
- and 200 yellow beads in another container - the 'female' container. In order to show
that it is a matter of chance whether a particular sperm meets a particular egg, mark 20 of
the red beads and 20 of the yellow ones with a black spot.
b Mix the beads in each container thoroughly. Now dip your hand into the male
container and pull out one bead without looking; do the same for the female container.
These two beads represent the zygote (fertilized egg). Look to see if either of the beads
carries a black spot.
c Keep a record of whether there was a black spot on the red bead, the yellow bead or
neither. Put the two beads into a third container.
d Shake the male and female containers and draw out two more beads. Repeat this until
you have made at least 50 zygotes.
Questions
1 How many times did you pick a red bead carrying the black spot?
2 How many times did you pick a yellow bead carrying the black spot?
3 How many times did both beads carry the black spot?
4 How many times do you predict that you should have picked beads that both carried
black spots?
This simple investigation should have demonstrated that it is a matter of chance which
bead you pick from each container. Fertilization is like that too, except that the male and
female gametes are much more different from each other than the beads were. So it
makes a big difference which sperm fertilizes which egg - and yet this is largely a matter
of chance.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B68
BREEDING WITH BEADS (SIDE 2)
Investigation 2: Using beads to represent the production of
genotypes in a population
This time you are going to model a mating between two tall plants. Both of these plants had one tall parent
and one short parent. And the alleles for short and tall are going to be represented by beads of different
colours. One colour (red, for example) is the dominant allele for tall and one (say yellow) is the recessive
allele for short. (Note: human height is not inherited like this - many pairs of genes are involved. But peas
and beans are either tall or short.)
a parent population represented by beads
To do
200 red beads 200 yellow beads
e Write down the proportion of 'tall' and 'short'
offspring you expect to get.
f Put 100 red beads and 100 yellow beads into the
'male' container. These will represent the alleles
carried by the pollen grains. Do the same into the
'female' container; these represent the alleles carried
by the ovules.
g Shake the beads in each container so they are
thoroughly mixed.
h Without looking take one bead from each
container; these two beads represent the alleles in
the zygote that will develop into an offspring plant.
They represent the genotype of the offspring.
There are three possible genotypes - two red beads,
two yellow beads or one of each colour. Note down
which of these you have selected.
i Put the two beads into a third container and make
another selection. Repeat this, recording each time
the genotypes of the zygotes.
j Write down the proportion of 'tall' and 'short'
offspring you expect to get. (Remember that the
heterozygotes, with one allele of each type, will
be tall.)
Questions
tall
alleles
males
5 How many zygotes of each genotype did you end up with?
100 red
100 yellow
gene pool
beads mixed
by shaking
producing genotypes
(fertilization]
genotypes
100 red
100 yellow
6 How many tall plants and how many short plants would there be in this collection of offspring?
7 How do the results compare with what you expected?
8 What other factors apart from chance may have affected which beads you picked?
short
alleles
females
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
SKIPPING A GENERATION
B69
Look at this family tree. It gives information about the hair colour of three
generations in a family. Two of the grandparents have red hair.
grandparents
(1st generation)
Mr and Mrs Davies
A
w
Mr and Mrs Jones
M
•
Key to phenotypes
brown
hair
red
hair
their children
(F, generation)]
grandchildren
(F generation)
»A
r " • i ' 1
[— ^- ] J -1-] marries /-S^ i /r\
i i^ W i v )
&
Tracy Simon Richard Paul Robert Emma
o
females
males
Questions
1 How many of the children (Fi generation) have red hair?
2 How many boys are there in the grandchildren (F2 generation)?
3 How many of the grandchildren have red hair?
4 How many uncles do the grandchildren have?
Many characteristics, such as hair colour, are controlled by genes. The
different forms of a gene are called alleles.
Parental phenotype
The allele for brown hair seems to 'overpower' the
form of the gene for red hair. Red hair only
Parental genotype
develops if there is no allele for brown hair. So we
say that the allele for brown hair is dominant. The
gametes
allele for red hair is recessive.
All the first generation of children inherit two
instructions (two alleles) for hair colour. They all
inherit an allele for brown hair and an allele for red
hair.
F, genotype
F, phenotype
5 Draw a diagram to show the alleles in the sex cells of Tom Davies and
Mary Jones. Also show the possible combinations of these alleles in the
grandchildren.
6 What can you say about the alleles for hair colour inherited by Emma and
Simon?
7 What can you say about the alleles for hair colour inherited by Tracey,
Richard, Paul and Robert?
© Nuffield Foundation 1996
brown hair
BB
red hair
bb

NUFFIELD BIOLOGY
SEX-LINKED INHERITANCE
B70
To study
Use textbooks to find out about haemophilia. Note that this family tree (unlike
the one in B69) tells us about genotypes as well as phenotypes.
Queen Victoria
Albert
Key
O
homozygous
male with normal
blood clotting
female with
normal blood clotting
Victoria
Albert
Edward
(King Edward VII)
Questions
Alice Alfred
O
Helena
1
Louise Arthur Leopold Beatrice
1 How does haemophilia affect people who inherit the disease?
2 What is the treatment for people with haemophilia?
3 How might a person having haemophilia affect others in the family?
4 Which chromosome carries the gene which determines whether or not a
person will suffer from haemophilia?
5 A man with normal blood clotting and a 'carrier' woman
want to have children. Copy and complete the diagram to
show the probability of each type of child.
6 If the mother is a carrier of haemophilia, what is the
chance that:
• a daughter will also be a carrier?
• a son will be a haemophiliac?
7 Explain the term 'sex-linked'.
8 Why is it very unlikely that a girl will inherit haemophilia?
Parental
phenotypes
Parental
genotypes
gametes
F, genotypes
and
phenotypes
9 Red-green colour blindness is inherited in just the same way. But it is
much more common. It affects 1 in 80 of males and 1 in 6400 of
females.Draw a diagram to show the probability of each type of child, if the
parents are a colour-blind man and a woman with two genes for normal
colour vision.
haemophiliac male
heterozygous (carrier)
female with normal blood
clotting
father with normal
blood clotting
XHY
carrier mother with
normal blood clotting
x
xHXh
oo oo
o o
( )
_ _ _ _ _ _
( ^
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
TWO INHERITED DISEASES
B71
Questions
1 How do inherited disorders differ from
infectious diseases such as flu?
2 Write short explanations of these terms
in genetics: alleles, dominant, recessive,
symptomless carrier, phenotype, genotype,
homozygous, heterozygous.
normal
Cystic fibrosis
3 What are the symptoms of cystic
fibrosis?
4 How does cystic fibrosis affect people's
lives?
5 Is the allele for cystic fibrosis dominant
or recessive?
6 Copy and complete this diagram to
explain the pattern of inheritance of cystic
fibrosis.
7 Is there any chance of a baby having
cystic fibrosis if only one parent is a
carrier?
8 What is the chance that a baby will be
affected by cystic fibrosis if both parents
are carriers?
Parental
genotypes
gametes
F, genotypes
and
phenotypes
carrier
father
Ff
carrier
mother
Ff
oo oo
o o
o
o
affected
by cystic
fibrosis
Sickle-cell anaemia
Here there are three different phenotypes (compare this with the inheritance of
colour in tomato plants, B66).
9 The homozygous condition, with two recessive alleles, ss, is called sicklecell
anaemia. Find out how the haemoglobin and red blood cells are different
in people with this condition. What are the symptoms?
10 The heterozygous condition, with one dominant and one recessive allele,
Ss, is called sickle-cell trait. How does this affect the blood? Why is this an
advantage in areas of the world where malaria is common?
11 What is the chance that a child will have sickle-cell trait if both parents
have sickle-cell trait?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
GENES
B72
To do
Complete the flow chart. Write a word or two or a sentence in each box.
The job done by
the nucleus of a
cell
The strands
seen in the
nucleus when
cells divide
The materials of
which genes
are made
If the
gene
for eye
colour
lies here
from mother
the gene
for eye
colour
lies in
the same
place
here
from father
The job of a
gene
part of DNA chain
gene L gene M gene N
codes for codes for codes for
protein L protein M protein N
Substances
formed in cells
underthe
control of
genes
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
GENETIC ENGINEERING
B73
To study
Find out how genetic engineering is used to manufacture human insulin for diabetics.
Remind yourself about the importance of the hormone insulin by going back to your notes
on hormones.
To do
Make a series of diagrams or models to explain how genetic engineers modify bacteria so
that they produce human insulin. Label the diagrams with the help of some of the
suggested captions in the grid below.
DNA strand
gene for human insulin
genes
cutting enzyme
double strand
of plasmid DNA
cutting enzyme
bacterium
/
bacteria grown on
industrial scale
normal bacterial DNA
The part of DNA molecule in a
normal human cell which controls the
production of insulin.
An enzyme cuts the circle of DNA in
a bacterial cell.
DNA molecule from a human cell.
Bacteria with the insulin gene produce
insulin on a large scale in a fermenter.
Enzymes, acting as chemical scissors,
cut the insulin gene from the human
DNA.
When cells divide they make copies of
their DNA, so each new cell has a full
set of its own DNA.
Bacteria reproduce very quickly. In the
right conditions bacterial cells divide
every 30 minutes or so.
Circle of DNA in a bacterial cell
(called a plasmid).
The bacterial DNA takes up the
fragment of DNA which includes the
insulin gene.
A genetic engineer switches genes
from the cells of one type of organism
to the cells of another organism.
Questions
1 Why do many diabetics need regular injections of insulin?
2 What are the main effects of insulin in the body?
3 Why do you think that insulin was the first product from genetic
engineering to come on to the market for the general public?
A gene provides the instructions for a
cell to do a particular job.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
GENETIC ENGINEERING - THE ISSUES
B74
Two radio reporters have just had a nasty shock.
They went out to interview a scientist working in
genetic engineering and plant breeding. When they
got back to the studio they found that the
microphone had not been working. So they have no
record of what the scientist said in reply to their
questions.
To study
Do some research on the uses and worries about genetic engineering. Then read the questions which the
reporters wrote down before the interview.
To discuss
Discuss the answers which you think the scientist might have given.
To report
• Use your suggested answers to make a tape recording of the interviews. Remember to put a short
introduction before the questions start. Round your programme off with a short summing up.
• Listen to a tape made by another group.
• Write a short review of the tape you listened to as if you were reviewing the programme for a
newspaper.
Q Please tell us something about the work you do.
A ...
Q What is the difference between plant or animal
breeding and genetic engineering?
Q Can you point to any successes of genetic
engineering? What are these successes, and how do
they improve our lives?
Q What is it about genetic engineering which seems
to worry the general public?
A ...
Q What can scientists do to help the public
understand the benefits and risks of genetic
engineering?
Q Do you have any worries about the effects of
genetic engineering? If so, what are the things
which you worry about?
Q What would you like to see happen in the future
with genetic engineering?
Q Who should control genetic engineering
research? Politicians? Scientists? The general
public?
A ...
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B75
CLONING A CAULIFLOWER (SIDE 1)
You are going to use tissue culture to grow cauliflower plants. You will have to be very clean in your work
to be successful. Read right through all the instructions before you start.
To do
a Prepare a sterile area by wiping part of
your work surface using a cloth soaked in
bleach.
b Cut out a small piece of the white part
(curd) of a cauliflower.
c Cut the curd into three small pieces
(explants) on a clean Petri dish.
corrosive
Take care with
the sharp
scalpel
d Drop the explants into fresh bleach
solution and leave them for 10 minutes
only.
e Use sterile forceps to transfer the
explants to some sterile water. Leave in this
rinsing water for at least 1 minute.
f Rinse the explants twice more in the
same way. Remember to resterilize the
forceps each time.
g Transfer each explant to a test-tube
containing a growth medium. Label the
tubes and cover them with aluminium foil to
reduce evaporation.
\
sterile water
sterile cotton
wool plug
sterile water
Ethanol
Sterilize forceps by
dipping them in ethanol,
then pass them briefly
through a flame.
To report
Keep an eye on your culture tubes regularly
for the next few weeks. Record your
observations with notes and drawings.
Continue until you have small plants ready
to grow on in pots.
sterile test-tube
containing
growth medium
explant transferred
using sterile forceps
foil cover
© in this format Nuffield Foundation 1996
From Practical Biotechnology: a guide for schools and colleges, National Centre for Biotechnology, University of Reading, 1993

NUFFIELD BIOLOGY
B75
CLONING A CAULIFLOWER (SIDE 2)
To do
h Open your culture tubes. Gently remove the
small plants and wash away any jelly from their
rootlets.
i Plant the small plants in moist peat in small pots.
Cover the pots with clingfilm. Stand them in a well
lit place away from draughts.
j After a week, make two small holes in the
clingfilm. Increase the size of the holes over the
next two weeks.
k After four to six weeks remove the clingfilm. About a week later the
cauliflower plants should be ready to plant in a cold frame or in a seed tray.
When they are strong enough you can plant them out in a garden.
To record
• Continue your notes and diagrams describing the growth of your plants.
• Draw a flow diagram describing the stages in tissue culture of plants.
© in this format Nuffield Foundation 1996

NUFFIELD BIOLOGY
PLANT AND ANIMAL CLONES
B76
Tissue culture
These diagrams show how tissue culture can
produce clones of a carrot.
transverse
section of
carrot
Cloning frogs
Cloning animals is not as easy as cloning plants.
The basic procedure is to remove the nucleus from
an unfertilized egg and replace it with a nucleus
from a body cell. In the early work the scientists
used the eggs of frogs and toads. More recently
scientists have managed to transfer the nucleus from
the liver cell of one rabbit to an egg cell from
another rabbit.
Questions
1 Why are clones identical?
2 What are the advantages of cloning for
producing many plants for agriculture?
3 Which methods of cloning are commonly used
by gardeners?
pieces of carrot
coconut milk
Qg>
1 free cells in
suspension
1 embryo from
CT\cultured
\\free cells
4 How does tissue culture differ from the methods used by gardeners?
5 Suggest some advantages and disadvantages of tissue culture compared
with cloning methods used by gardeners.
6 a Why is it more difficult to clone
animals than plants?
b Why is it more difficult to clone
mammals than amphibians such as
frogs?
7 In the experiment to clone rabbits,
which rabbit will the baby look like?
liver cell
from rabbit 1
egg cell
from rabbit 2
nucleus
removed
nucleus taken from
liver cell and put in
egg cell
8a Suggest reasons why scientists are interested in finding ways to clone
farm animals.
b Suggest possible disadvantages of cloning farm animals.
9 It is illegal to try to clone humans.
a Why do you think that Parliament has banned attempts to clone people?
b Can you think of circumstances in which the cloning of people should be
allowed?
plantlet
flowering plant
cells form
embryo
egg placed in womb
of rabbit 2
baby rabbit
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
SELECTIVE BREEDING
B77
Charles Darwin made a detailed study of plant and animal breeding ('artifical selection') while working on
his theories of natural selection and evolution. He was interested in variations in animals and plants, and
breeding new varieties. Compare the diagrams of bread wheat and wild wheat. They show what plant
breeders can do to produce high-yielding crops.
To do
a The pictures and captions below describe breeds of cattle. Cut out the boxes and match each
animal with its caption.
b Sort the matched pairs of boxes into two groups: cattle bred for meat and cattle bred for milk.
Questions
1 Which breed of cattle might be used for both milk and meat production?
2 Cattle breeders sometimes cross Highland bulls with other breeds of cattle.
What advantages might this give?
3 Compare the drawings of wild wheat and bread wheat.
a Make a list of the differences.
b How do the differences help to increase crop yields?
4 Use library books to find out about different breeds of dog. Choose about five
which have been bred for different purposes (e.g. sheep-dog, retriever, pet).
Which characteristics have been emphasized by selection in each case? wild wheat bread wheat
Jersey 390 kg 500kg
Hereford
440kg
Friesian 600kg Simmental 730kg
3 Short-legged cattle which are bred
for meat. They are not as heavy as
some breeds but they can withstand
extremes of temperature.
1 These small cattle produce milk
with a high level of fat suitable for
making butter.
2 One of the largest breeds of cattle.
They are bred mainly for meat, and
produce only 20 per cent less milk
than the Friesian.
4 Cattle which are slow to mature.
They are long-haired, which helps them
to survive in cold conditions. They live a
long time and are often used for milk
production.
5 A common breed of large cattle with
well developed udders. This breed
produces large amounts of milk.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY_____________B78
POTATO CYST EELWORM AND
POTATO BLIGHT
'In 1845 a man passed through a certain district on his
way to Cork for a week's stay with some relatives. On
his way south all looked well. On his way back, however,
the whole parish was stricken as if by frost and the fields
were black with devastated foliage. 1
(from Seeds of change: five plants that transformed
mankind by Henry Hobhouse, Papermac, 1992)
This is a description of the effects of the most lethal killer of potatoes - blight, caused by the
fungus Phytophthora infestans. A million Irish people died during the next few years.
Today, blight and potato cyst eelworm can cost farmers a lot of money. Fortunately the gene
bank of the potato contains much variation, which potato breeders can use to fight back.
• Visit your local supermarkets and greengrocers. Make a list of all the varieties of potato on sale.
Questions
1 Who sold more varieties of potatoes, the greengrocers or the supermarket?
The potato varieties sold in the shops have been produced by breeding from the original
varieties.
Many wild varieties of potatoes are resistant to potato pests. The 'gene bank' is large. At the
International Potato Centre in Peru there are 12 000 varieties of potato. Plant breeders have used
this gene bank to breed varieties such as Sante, Pentland Javelin, Cara, Penta, Skirza, Kingston
and Maris Piper. Sante, Pentland Javelin, Cara, Penta Skirza and Kingston are resistant to
potato cyst eelworm; Maris Piper and Cara are resistant to blight.
If a wild variety of potato contained a gene which gave resistance to potato cyst eelworm, it
would be useful to transfer this resistance to a cultivated type. A cultivated potato may have
desirable features such as making good chips, but that is no use if you need to grow it in an area
infected with eelworm.
2 From the work you have done in genetics, make a list of the ways in which a potato breeder
might transfer this resistance from a wild variety to a cultivated variety.
Sometimes fertilization will not work between different varieties, even if they are of the same
species.
3 Which method in your list would not work if this were the case?
4 If breeders transferred the resistance to eelworm gene by pollination with a wild variety, why
would they transfer a lot of unwanted genes as well as the gene causing resistance?
5 What do you suggest breeders do to get rid of the genes which they don't want, yet keep the
genes giving resistance to eelworm?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
FOSSILS
B79
To do
These sentences are in the wrong order. Rearrange them to make a paragraph about fossils.
Sometimes the animal itself is not found - only the tracks or burrows it made in the sediment survive in
the rocks.
To be preserved, animals and plants have to end up in places where they can be buried before
disintegrating or being eaten.
So fossils do not tell the whole story of life - they are more like clues which can help to build up a picture
of what organisms looked like and how and where they lived.
Countless creatures and plants must have lived on Earth without leaving a trace.
Only very occasionally are remains of soft parts found in rocks.
Usually it is the hard parts, the skeleton or the shell of an animal, that are preserved.
Fossils are organic remains, buried by natural processes and permanently preserved.
a Look at the three pictures of fossils, and, if possible, samples of similar fossils.
b Read the list of three ways that fossils can form.
c Match each picture with the way you think the fossil formed.
1 Most living things rot when they die. This can take a long time.
Sometimes only the soft parts rot, leaving hard parts such as bone,
teeth or shells.
2 Living things do not rot if they die in conditions which prevent
decay. Living things may be preserved as fossils if they die in a
peat bog or in a very dry desert region. Insects trapped in resin
may be preserved when it turns to amber.
3 Sometimes organisms die in conditions which allow minerals to
replace the organic materials as they decay.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B80
A THEORY BASED ON NATURAL SELECTION
To study
Read some of Darwin's writing about artificial and natural selection.
To do
The list below is a set of key terms to do with Darwin's theory of evolution.
Show that you understand the theory with the help of a 'concept map' linking
the key terms.
Write the concepts on 'Post-its' or small pieces of paper. Put them on a large
piece of paper and arrange them in a way which makes sense to you. Draw
lines between the linked concepts. Write notes and explanations beside the
lines.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
HOW MANY OFFSPRING?
B81
To study
Find out what Darwin wrote about
numbers of offspring.
Orders of magnitude
When making estimates, scientists often think in terms of orders of
magnitude: a hundredth, a tenth, one, ten, one hundred, a
thousand, ten thousand, a hundred thousand or a million. Going
from one order to the next involves multiplying or dividing by 10.
To do
Birth: make an order-of-magnitude estimate of the numbers of offspring produced in a lifetime by some
plants and animals.
Choose one or more of the following:
• the number of eggs laid by an animal (herring, stick insect, butterfly,
bird, frog or chicken, for example),
• the number of offspring produced by an animal which is a mammal
(cat, dog, mouse, hamster or cow, for example),
• the number of seeds produced by a plant (pea, lupin, broad bean,
geranium, groundsel, dandelion or tomato, for example).
For animals: estimate the number of young produced in a season and the number of times the animal
reproduces in its lifetime.
For plants: estimate the number of seeds in a fruit, the number of fruits on the plant, and the number of
times the plant produces fruit in a lifetime.
Questions
1 Use the table to label a copy of this pie chart showing the factors which affect the
survival of cabbage white butterflies.
Stage in the life cycle
Caterpillars killed by disease
Caterpillars killed by parasites
Caterpillars eaten by birds
Pupae killed by disease
Pupae killed by parasites
Healthy adults
Percentage
59.0 ,
34.0
2 Consider the stages in the life cycle of frogs. What are the factors which
control how many frogs' eggs survive to become adult frogs?
4.0
2.5
0.2
0.3
3 In The Origin of Species, Darwin gives an estimate made by the naturalist Linnaeus.
Linnaeus imagined a plant that lives for only one year producing just two seeds. He
assumed that each year the two seeds would germinate, grow, flower and each produce
two more seeds. He calculated the number of plants after 20 years. What answer did he
get?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY_____________B82
DARWIN'S CENTURY (SIDE 1)
Darwin's Century was a collection of 431 books about evolution. The
collection was sold at Sotheby's on 11 December 1992. Your teacher will give
you an extract from the catalogue which describes some of the books in
Darwin's Century.
To do
• Find another person in your class with an extract about a book which
presents a different view about evolution from your extract.
• Find out a few details about the two books and their authors and
summarize this information for the flaps on the book covers.
Question
• Why were Bishop Samuel Wilberforce ('Soapy Sam') and Thomas Henry
Huxley important in the controversy about Darwin's theory? Make a poster
advertising the debate between them.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B82
DARWIN'S CENTURY (SIDE 2)
Extracts from the 'Darwin's century' catalogue
AGASSIZ, Jean Louis Rodolphe An essay on classification, 1859
'No sharper contrast between the assumptions of special creationism and the concept of
evolution of species ever appeared.' [Agassiz supported special creationism.]_______
CUVIER, Georges, baron de Essay on the theory of the Earth, 1813
'The vast changes detailed in the fossil record were not reflections of evolutionary
development but the history of a series of catastrophes.'______________
DARWIN, Charles On the origin of species by means of natural selection, 1859
'Species have changed and are still slowly changing by the preservation and accumulation
of successive slight favourable variations.' ____________________
HUXLEY, Thomas Henry Macmillan's Magazine, 1859
'Mr. Darwin's hypothesis of species will take its place among the established theories of
science.'
OWEN, Richard: Letter to Spencer H. Walpole MP, 1882
'Charles Darwin stands to Biology in the relation in which Copernicus stood to
Astronomy.'____________ ___ ____________
WALLACE, Alfred Russel Social environment and moral progress, 1912
The theory of Natural Selection as expounded by Darwin was so completely successful.'
LYELL, Charles The geological evidences of the antiquity of man ... with remarks on
theories of the Origin of Species by Variation, 1863
'I always feel as if my books came half out of Lyell's brain.' (Charles Darwin)_________
CHAMBERS, Robert Vestiges of the natural history of creation 1844
This outspoken statement of a belief in evolution, published anonymously, anticipated
Darwin's Origin by fifteen years and generally prepared the public for Darwin's theories.'
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
SELECTION IN ACTION
B83
Here is some information about two species of prey. They have the best chance of surviving predation if
they are well camouflaged. Activity B84 lets you act as predators in model of this type of selection.
To study
Peppered moths
Moth collecting was a hobby for some people in
Victorian times. Most collectors had specimens of
peppered moths in their collections. The moths
were usually a speckled grey colour. In 1884 a
black form of the moth was discovered in the
Manchester area. By 1895, 95 per cent of peppered
moths in this region were black.
Speckled grey and black forms of peppered moth on tree trunks
Questions
1 Suggest a possible cause of the black form appearing in the population.
2 Suggest an explanation for the rapid increase in the percentage of the black
form in the Manchester area.
To study
Snails
Collecting snail shells from a thrush's 'anvil' makes it possible to find out the
proportion of the differently coloured and patterned snails the thrush has found
and eaten at different times of year.
The figures in the table are based on observations at a thrush's anvil in a
wood near Oxford. The scientists were studying snails of the species
Cepaea. The proportion of yellow snails living in the wood
was the same in April and June.
The graph shows the results of observations of the same
species of snail made in woodland, and in hedgerows and
grassland. Each point on the graph shows the results from
observations at a particular 'anvil'.
Questions
3 What is a thrush's anvil?
4 Why do you think the thrushes near Oxford
caught fewer yellow snails in June than in April?
5 Look at the graph:
a Are you likely to find more banded or unbanded snails in woodland?
b Which varieties of snail are more common in hedgerows and grassland?
6 What might happen to the number of yellow snails if the amount of
woodland became very much less?
© Nuffield Foundation 1996
S?
100
90
Month
April
June
Collected shells that
were yellow(%)
42
22
80 " o o 0 ° • o
70
60
50
40
30
20
id
n
• deciduous woods
o hedgerows and
o o grasslands
t°-.*V
° 0°°°
cP ° o o o o °
0
00 a*
°°°. . '.
• \ . • ,
0 ° 0 0 °
- • * » 0 f • • • |
• 0 . • 1
• *- •
1 1 1 1 1 M 1. 1* -« ——— L—— -1
% with one or no band

NUFFIELD BIOLOGY_____________B84
USING MODELS TO EXPLAIN SELECTION
(SIDE 1)
Charles Darwin was a keen naturalist. During his life, he made many
observations but four of them were important enough to change the way
people thought about life. These four observations, together with three
deductions, are set out below. These ideas eventually led Darwin to produce
his Theory of Evolution.
1 Living things have the potential to produce more offspring than are needed to replace
themselves.
2 The number of organisms in the wild however usually remain the same.
• Darwin concluded that some organisms must die before they reproduce.
3 Most living things show variation. No two individuals are usually alike.
• Darwin concluded that the 'fittest' or best adapted organisms survived.
4 Some types of variation are passed on from parents to their offspring.
• Populations -will slowly change or 'evolve' as successful parents pass on
characteristics to their offspring._____________________________
To do
Which 'rice grain creatures' are best adapted to avoid predation?
a You are supplied with a container of vermiculite. Mixed with the
vermiculite are 100 rice grains which represent a population of small
organisms. The rice grains differ in colour. There should be 50 of each colour
at the start of your experiment.
b Use a pair of forceps to pick out as many grains as possible. Your partner
will time you for 1 minute. This represents predation.
c At the end of this time, count how many rice gains of each colour you have
removed. If the total number of rice gains is an odd number, pick out one
more grain. Use your results to work out how many grains of each colour are
still in the container.
d Make up the number of rice grains in the container to 100 by adding equal
numbers of each colour. The population of small organisms will now contain
different proportions of each colour. Make a note of these results. This
represents reproduction, keeping the size of the population constant.
e Shake the container to mix the grains with the vermiculite. Now time your
partner for 1 minute whilst further rice grains are removed. Repeat steps c and
d several more times to see how the population changes each time. This
represents survival of the fittest.
• Record the results of the experiment in a table like the example shown.
• The results can be plotted to show how the populations change with time.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B84
USING MODELS TO EXPLAIN SELECTION
(SIDE 2)
Colour of Vermiculite: blue
Colours of rice grains: i) red and ii) blue
Generation
Number of grains removed
Number of grains replaced
Percentage of population
colour i)
colour ii)
colour i)
colour ii)
colour i)
colour ii)
red
blue
red
blue
red
blue
Parents
Nil
Nil
Nil
Nil
50
50
1st generation
12
4
8
8
46
54
2nd generation
10
4
7
7
43
57
3rd generation
14
6
10
10
39
61
etc.
To do
Taking the experiment into the field
Which 'pasta caterpillars' are best adapted to avoid predation?
If you have a grassy area in the school grounds, you might like
to try this investigation using 'pasta caterpillars'.
a Set out alOmxlOm square and place a marker at
each corner.
b Partly cook 100 pieces of spaghetti. Use food
colouring to dye 50 pieces green. Leave the others
yellow. (Alternatively, you can buy pasta in two
different colours and cook it.)
c Use strings to divide the 10 m square into 100 one
metre squares.
d At each intersection, place one piece of pasta. Do this
randomly but make a note of which colour is at each
intersection.
e Over the next few days, note which pieces of pasta
are removed and eaten by birds.
Questions
1 Account for the results you obtained in your experiments.
// / / / /
pasta caterpillars
peg
\L_ABCD_EFGHJ_jJ
2 In the first experiment, the total number of rice grains was kept at 100. Why was this important?
3 What assumptions have you made about the 'predators' in these experiments?
i
i
3
4
5
/)
y
&
8
yy
c
&
y
x>
G-
(r
£
Y
6-
f
G-
y
6-
y
G-
H
6-
y
i
6-
y
3"
y
6-
sample data sheet
Y = yellow pasta
G = green pasta
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B85
NEW TYPES OF FLU (SIDE 1)
To study
'Coughs and sneezes spread diseases.' This is true of the flu virus, which we pass on in water droplets
when we sneeze. Flu spreads rapidly if people are close together, especially if they are under stress so that
their resistance to disease is lower. Use reference material to find out about changing viruses.
Questions
1 What causes flu?
2 Patients build up immunity to flu when they get the disease or are
vaccinated. So why can people keep getting flu year after year?
To do
A flu outbreak spread across the world in 1918 just before the end of the
World War I. The first reports of the outbreak came from a military base in
Kansas, and from there it spread rapidly across the USA into Europe and
Asia. Estimates suggest that the epidemic killed between 20 and 40 million
people - four times as many as died in the war. The epidemic reached Europe
in the spring of 1918. The table shows when cases were first reported in the
towns listed.
''June
Diffusion of flu
^first wave, spring 1918
April 1918
May 1918
June 1918
July 1918
Brest
Toulouse
Paris
Granada
Warsaw
Bordeaux
Marseilles
Lyons
Barcelona
Odessa
Le Havre
Lisbon
Brussels
Amsterdam
Madrid
Oporto
Stockholm
Glasgow
Seville
Vienna
3 Record the spread of the flu on the map on the diagram sheet. Write in the names of the
places affected. Use a different colour for each month.
Draw lines linking the places first affected in the same month.
4 Why do you think the flu outbreak spread so fast and killed so many people in 1918?
5 What do you notice about the pattern of the first European outbreaks?
6 There was a second outbreak of flu in the autumn of 1918. The first cases were reported at
Brest, one of the main arrival points for American troops. This second outbreak killed many
millions who had survived in the spring.
a What does this information suggest to you about the virus causing the second outbreak?
b Why is it significant that the outbreak was in Brest?
7 Imagine that you were a member of a team advising the New Zealand government. Ministers
wanted to know how to stop the virus spreading to New Zealand civilians when troops came
back from Europe at the end of the war. What advice would you have given them?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B85
NEW TYPES OF FLU (SIDE 2)
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
PATTERNS IN THE DISTRIBUTION OF A
SIMPLE PLANT
B86
Todo
a Have a close look at a tree trunk, looking for the tiny single-cell plant called Pleurococcus growing on it.
Questions
1 Where does it grow:
• on vertical surfaces?
• on horizontal surfaces?
• in the sun?
• in the shade?
2 Does the tree stand by itself, or is it shaded by other trees or buildings?
3 What conditions does Pleurococcus need in order to live, and from where does it get them?
4 How will environmental conditions, particularly light and water, vary around the tree during
the course of a day?
Todo
b Carefully draw the base of the tree trunk from the north and from the south. Indicate where
Pleurococcus is found by shading on your drawing. If you look at the tree a little more closely
you might find that the green patches are more dense in some areas than others. If so, make
your shading a little darker in these places.
c Often the green patches are uneven, and do not cover the whole area. Mark a piece of string
at 10 cm intervals. Fix it around the trunk of a tree about 1 to 1.5 metres above the ground
(above dog height!).
d Place a quadrat, 10 cm x 10 cm, on the string at one point. Find out the density of the
Pleurococcus by estimating what percentage of the bark under the quadrat is covered with it.
e Move the quadrat on to the next position on the string and repeat your estimation.
successive positions of quadrat frame
- horizontal string
tied around tree
• Wash your hands when you have worked your way all round the trunk.
f Display your results as a bar chart, showing percentage cover against aspect (that is the
direction the trunk faces).
Question
5 How can you account for the patchy distribution of the plant?
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B87
INVESTIGATING PLANT POPULATIONS (SIDE 1)
Decide on your investigation. You will have to choose a suitable method for sampling
plant populations (see side 2).
Some starting points for investigations
• How does trampling or mowing affect the numbers of dandelions, daisies, or other
plants, growing in grassland?
• Does the steepness of a slope affect plant populations?
• How does shade affect plant populations?
• Do north and south facing slopes have similar plants growing on them?
• Do you find similar plants in damp ground and dry ground?
• How do plants affect each other when they grow close together?
• Are plants spread out evenly where they grow or are they in clumps?
• What plants can you find on vertical surfaces such as walls, tree trunks or fence posts?
Check safety
dandelion
(25 cm)
daisy
(6cm)
buttercup
(25 cm)
clover
(5 cm)
ribwort plantain
(30 cm)
groundsel
(30 cm)
nettle
(100cm)
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B87
INVESTIGATING PLANT POPULATIONS (SIDE 2)
Quadrat surveys
Imagine you are interested in the effects of trampling on
dandelions. Choose two or three areas of the school field
which get different amounts of wear. This could be a path,
a goal mouth and ordinary turf. Sample each area with
your quadrat a number of times.
Each time you put down a quadrat, count the number of
dandelion plants that you find inside it. Note the number.
Work out an average value for the number of
dandelions in a square metre for each area. You could
use this method to investigate different species and
different growing conditions around your school site.
The quadrats allow you to take a sample of the population.
How you make sure that this is a random sample (rather
than a sample chosen by you because it looks more
interesting)?
*~''
f>* •',.... ' -
Making a belt transect
A belt transect is a good way to investigate
how conditions, which vary over a short
distance, affect a population of plants.
For instance, you can lay a long tape
from the base of a tree in a park. At one
metre intervals, record the light intensity
using a light meter. At the same time count
the number of your chosen species which
lie within a 1 m x 1 m quadrat.
Your transect study will give you a series of
pairs of numbers. From a transect under a
tree, for example, you will record at one
metre intervals:
• the number of your chosen plants
species in a quadrat, and
• the light intensity.
You can display the data by plotting two bar charts. One of number of plants against distance, the other of
light intensity against distance. Comparing then helps you to find out how light affects your chosen species.
Alternatively, you could plot a scatter graph, with light intensity on the ;c-axis and number of plants on the
y-axis.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
RED SQUIRRELS
B88
North American grey squirrels were released at Woburn, Bedfordshire in 1890. Since then they have
become established in deciduous woodland throughout the UK. From 1940 on there has been an equally
spectacular reduction of numbers of red squirrels in deciduous woodland areas of the UK. Britain and
Ireland are the only places where both squirrels are found.
Squirrels have a varied herbivorous diet, but in autumn they depend on tree seeds for food (e.g. nuts and
the seeds in pine cones). It was suggested that the fall in red squirrel numbers in deciduous woodlands was
something to do with acorns. Here are some findings from studies of squirrels in deciduous woodlands:
• Grey squirrels foraging for tree seeds did 86% of this on the ground.
• Red squirrels foraging for tree seeds did 33% of this on the ground.
• Fallen tree seeds are the main winter food when snow or frost make stored seeds unavailable.
• The peak summer densities of red and grey squirrels in oak and hazel woods in Hampshire were:
Red squirrels per hectare in wood 1
Red squirrels per hectare in wood 2
Grey squirrels per hectare in wood 3
Grey squirrels per hectare in wood 4
Acorn crop in previous autumn
Density of squirrels in the summer of
1984
0.6
1985
1.1
1988
4.7
3.7
Fair
1986
0.8
0.9
7.7
6.7
Good
1987
0.9
1.3
2.4
2.8
Poor
4.9
Good
Fair
• When six captive young squirrels of each species were given a mixed diet of hazelnuts, peanuts,
sunflower seeds, apples and carrots, it was noticeable that the red squirrels did not eat the acorns whereas
the grey squirrels ate these as well as the other seeds. Even when the proportions of the other seeds were
reduced the red squirrels remained reluctant to eat the acorns.
• Analysis of faeces showed that red squirrels digest acorns only 78% as efficiently as grey squirrels.
• Acorns contain polyphenols, which inhibit digestion. Red squirrel faeces contain 87% of the
polyphenols of the original acorns, whereas grey squirrel faeces contain only 37% of the polyphenols of the
original acorns.
• Here are pre-breeding density and breeding success correlated to tree seed availabilities.
Grey squirrel
Red squirrel
Squirrels per hectare
correlation with
acorns
significant
not significant
correlation with
hazelnuts
not significant
significant
Young per adult female squirrel
correlation with
acorns
significant
not significant
correlation with
hazelnuts
not significant
significant
• In continental Europe, the red squirrel is found in coniferous forests. In Britain, it often lives in
deciduous woodland.
• Hazel trees have been rapidly disappearing from British woodlands, but oak trees are still abundant.
Questions
Use this evidence to try to answer these questions.
1 Do you think both squirrels are competing for the same food?
2 Do you think both squirrels are competing for the same shelter?
3 How has the environment changed, since 1940, in favour of the grey squirrel?
4 Imagine you own a large mixed woodland. Design a long-term investigation to find out whether the
presence of grey squirrels, on other factors in the environment, are mainly responsible for the red squirrels'
decline.
5 What steps could be taken to encourage the return of the red squirrel?
© in this format Nuffield Foundation 1996
Based partly on 'What future for British red squirrels?' by R E Kenward and J L Holm, Biological Journal of the Linnean Society,
38, 83-9, 1989

NUFFIELD BIOLOGY
TYPES OF POLLUTION
B89
To study
Look carefully at the picture below and work out how many kinds of pollution you can see.
To record
Make a table to summarize all the types of pollution you find.
Type of
pollution (air,
land, water)
Where the
pollution conies
from
The main
pollutant(s)
The damage
done by the
pollutant
How to stop the
pollution
oiljanker
© Nuffield Foundation 1996

B90
NUFFIELD BIOLOGY
MONITORING WATER POLLUTION (SIDE 1)
To study
You can compare pollution levels in stretches of
fresh water by studying the animals you find.
Catch your animals by the same method, taking the
same time, in each place. Scoop up some of the
bottom material and examine it for animals in a tray
or stir up the bottom material and catch the animals
in a net placed downstream.
Look at your catch in a tray. Check the animals you
find against the indicator animals chart (side 2).
When you have counted the animals, pour the
animals gently back into the pond or stream.
You may find animals from more than one pollution
level in the same place. If so, you'll have to decide
on numbers. For instance if you have 25 stonefly
nymphs and 1 sludge worm you can assume that
the water is clean.
Remember,
any water can
be dangerous.
Your teacher
will give you
strict
instructions on
how to do this
survey.
your teacher may wish
you to wear disposable
plastic gloves
Cover any cuts
and grazes
with
waterproof
dressings
before starting
your
investigation.
Never work
near a sewage
outfall.
To study
Find and study some information about water pollution. -
Questions
1 This table shows the results of a study of two streams.
Total biomass in the sample / g
Stream A
Stream B
Mayfly nymph
4
0
Caddis fly larva
30
0
Freshwater shrimp
70
1
Water louse
34
4
Bloodworm
10
45
Sludge worm
2
100
a Present the data in the table graphically in a form that will help you to compare the two streams.
b Suggest hypotheses to explain the differences.
© in this format Nuffield Foundation 1996

NUFFIELD BIOLOGY
B90
MONITORING WATER POLLUTION (SIDE 2)
Animal found
Pollution level
Stonefly nymph (about 10 mm) Mayfly nymph (about 20 mm) A Clean water
Freshwater shrimp (about 20 mm) Caddis fly larva (about 10 mm) B Some pollution
Water louse (about 10 mm) Bloodworm (about 20 mm) C Moderate pollution
Sludge worm (about 120 mm) Rat-tailed maggot (up to 55 mm) D High pollution
No life E Very high pollution
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
NITRATES IN WATER
B91
To study
The European Community (EC) has agreed on a legal limit to the amount of
nitrate allowed in drinking water. The limit is 50 mg per litre.
These figures for nitrate in water samples taken in 1991 show that some water
supplies in Britain are over the limit.
Dartmoor reservoir water
E. Anglian underground water
River Severn water
Bottled mineral water
To do
Use test strips to measure the level of nitrate in
water samples.
a Dip the test zone of the strip into your water
sample for 3 seconds.
b Shake the strip dry and, after 1 minute, read off
the nitrate concentration from the colour chart.
3.0 mg per litre
65 .Omg per litre
35.0 mg per litre
6.0 mg per litre
nitrate
__ reaction strip
sample
being tested
To study
Find out more about the effects of nitrates and the variables that affect nitrate
concentrations.
To investigate /1 / •
Plan an investigation into the nitrate levels in water samples. Check safetv
Here are some possible investigations which you might carry out with nitrate test
strips:
• the nitrate concentration in various soil samples,
• the nitrate concentration in sap from various vegetables,
• the nitrate concentration in water in various rivers, ponds and streams.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
ACID IN THE AIR
B92
Todo
a Put a container with seedlings in a large plastic
bag. Soak a wad of cotton wool in water, place it in
a dish, and use tweezers to add a Campden tablet
which will release sulphur dioxide. Place the dish in
the bag. Seal and label the bag.
b Set up another similar bag, but this time use
damp cotton wool without a tablet. Others in the
class will set up similar pairs of bags with different
seedlings as shown in the diagram.
c Watch what happens to the seedlings in the bags
Look at them at the end of the lesson and then over
the next few days.
Sulphur
dioxide
To study
Look at the two pictures on this page.
To report
• Describe what happens to
the seedlings in the plastic
bags. What can you learn
from the results?
• Many people are muddled
about air pollution and its
effects. Imagine that you
write a regular 300-word
column about science issues
for a local newspaper. This
week you are going to
explain 'acid rain' to your
readers. Write a draft of
your article ready for the
editor.
Primary pollutants
sulphur dioxide
nitrogen oxides
\ \\
emissions \ \ \
A A A \ \ ^
tt effects on
chemical
reactions
stimulated
by sunlight
people, buildings')
trees \
^
Secondary
pollutants
sulphuric acid
nitric acid
M\\
M\\
M \ \
/ \ \ \
dry deposition -gases,
specks or droplets
...----^'ffects on trees'-
and crops
effects on soil
incorporated
in rainfall
===>,
effects on water
plants and fish
' .effects on trees,
rivers, lakes
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
B93
HOW DO POLLUTANTS AFFECT CHLORELLAt
To study
In this activity you are going to investigate the effects of pollutants on the
growth of a micro-organism called Chlorella. Chlorella is a green alga.
Apparatus
mains lamp
'Chlorella culture
,light sensor
to data
logger
magnetic stirrer
Procedure
a Three-quarters fill the jar with culture solution. Then add about 50 cm3 of
a rapidly growing Chlorella culture.
b Switch on the logger and start to collect data at regular intervals. Either log
continuously for 24 hours, or run the logger for 6 hours or so on a number of
successive days with each day's data stored on disc.
To do
Design an investigation to study the effect of pollutants such as warm water,
acids, detergents, pesticides or nitrates on the growth of Chlorella,
Study the diagram of the suggested apparatus, note the procedure, then
design your investigation. You will probably have to combine with other
groups to carry out the investigation and share results.
Check safety
© in this format Nuffield Foundation 1996 Based on Toolkit science, Reproduced by courtesy of the University of Leicester

NUFFIELD BIOLOGY
GLOBAL WARMING
B94
Two quotations
'Waiting will serve no purpose. Our planet faces climate change such as never
happened before. In the face of possible catastrophe, we cannot wait for certainty.
We know enough right now to begin.'
'Despite all the uncertainties about the greenhouse effect, few scientists who
study the climate doubt that global warming is a real problem. They tell us that
the time to plan counter-measures is now. Above all, they argue, we must use
energy more efficiently. They do not say that we should wait another ten years
for scientific proof of the greenhouse effect.'
___
To do
Imagine a group of people who are worried about the greenhouse effect. They
have decided to make changes in their way of life to cut down on the amount
of greenhouse gases going into the air. Each week they meet to tell each other
what they have done. Here are some of the things they say they did last week.
to work
of going
I gave money to a
charity which works
in developing
countries.
I bought a garden table
and chairs made of
wood instead of plastic.
got rid of our
deep freeze -the scrap
metal merchant took it
away for me.
I bought shares
in Nuclear Electric.
I replaced our
solid fuel boiler
with a gas boiler.
replaced a broken
filament lamp bulb with
one of the new
fluorescent bulbs
To discuss
catalytic converter
fitted to my car.
I had loft insulation
fitted to my house.
1 Divide the people's actions into three groups:
• actions which help to cut down on greenhouse gases going into the air,
• actions which have little or no effect,
• actions which might do more harm than good.
2 Can the actions of individuals help to solve worldwide problems such as
the harmful consequences of the greenhouse effect?
put the
garden rubbish
onto a compost heap
instead of burning
it.
decided to
give up smoking
decided notto
mow the lawn.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY_____________B95
IN DEFENCE OF MODERN FARMING
Todo
Collect information about different farming methods from sources such as
supermarket leaflets and farming magazines. Look for views supporting very
different farming methods.
Compare organic farming with modern intensive methods. Consider:
• the varieties of crops grown and animals reared,
• the sources of nitrogen compounds and other plant nutrients,
• the range of animal types,
• ways of looking after animals,
• ways of dealing with pests and diseases,
• the treatment of wastes,
• the quality of the produce,
• the impact on wild plants and animals.
To discuss
• What are the important issues which people ought to be worried about?
• Which aspects of farming matter to you?
• Given the choice do you, or your family, buy organic produce?
• What would you say to someone who takes a different point of view?
To report
Choose a way of reporting on your findings and discussions. You might:
• write notes summarizing the main points,
• sketch and label drawings which compare in words and pictures the
differences between the two approaches to farming,
• take on the role of a farmer and prepare to debate the issues with a farmer
taking a different point of view,
• record a discussion on audio or video tape.
When you are getting ready to report on your discussion of the issues think of
your audience and how you will interest them in what you have to say,
display or write. You will probably do better to avoid presenting one complete
point of view and then the other. Your account is likely to turn out better if
you tackle the issues one at a time. For instance a section on 'drugs in
farming' might start with the argument in favour with some evidence. Then
you could explain the argument against with its evidence. Finally sum up your
opinion or the opinion of the group.
© Nuffield Foundation 1996

B96
NUFFIELD BIOLOGY
PLANT PROTECTION IN THAILAND (SIDE 1)
Okra is becoming an important crop in Thailand's economy. The country exports okra to
Japan and European countries. The cotton bollworm is a serious pest, which damages the
okra flowers and seed pods.
Farmers have attempted to control the pest using insecticides but the bollworm
is becoming resistant to several pesticides. As a result farmers have to use large
doses of the pesticide. This is expensive and leads to poor quality okra.
Research scientists at the Department of Agriculture in Bangkok decided to find out if
they could use a virus to control the bollworm. They chose a virus that infects the larvae.
One trial began in February 1990 and continued until May 1990. The scientists sprayed a half-acre plot of
okra on a farm once a week with the virus. They sprayed another half-acre plot on the same farm with a
mixture of insecticides from a high-pressure pump-sprayer.
Over the next four months the scientists sampled fifty plants from each plot. They counted cotton bollworm
eggs and larva. They also noted the numbers of flowers and pods damaged by the pest.
The cost of the virus treatments was one and a quarter times higher than the total cost of the insecticides.
okra
Plot treated with the virus
Plot treated with insecticide
Date of
sampling
in 1990
Day
Eggs
Larvae
Damaged
flowers
Damaged
pods
Eggs
Larvae
Damaged
flowers
Damaged
pods
16Feb
1
8
10
0
4
10
14
1
6
20Feb
5
10
12
4
6
12
16
8
6
26Feb
11
26
14
3
5
26
15
16
15
5 Mar
18
14
3
4
0
30
22
9
13
12 Mar
25
22
6
2
10
28
16
3
10
21 Mar
34
10
9
7
12
40
64
24
44
4 Apr
48
19
3
1
1
49
13
16
5
7 Apr
51
16
6
12
10
21
17
15
11
11 Apr
55
6
4
4
6
16
24
7
17
17 Apr
61
0
6
1
0
8
22
7
16
24 Apr
68
0
3
1
3
0
14
4
12
1 May
75
7
3
0
3
6
10
2
6
9 May
83
0
1
2
5
0
10
1
13
15 May
89
0
3
-
4
0
14
-
8
© in this format Nuffield Foundation 1996. Data from Ketunuti, U, Tantichodok, A and Nanta, P, The use o/Heliothis armigera
Nuclear polyhedrosis virus to control Heliothis armigera (Hubner) on Okra, Reproduced by courtesy of Mr Ampol Senanarong,
Director-General, Department of Ariculture, Bangkok, Thailand

NUFFIELD BIOLOGY_____________B96
PLANT PROTECTION IN THAILAND (SIDE 2)
Questions
1 Select data from the table and use it to draw a graph which helps you
compare the effectiveness of the two ways of controlling the pest.
2 Can you find evidence to suggest that the virus infects the larvae?
3 Can you tell from the data which form of the insect does most damage to
the crop: eggs, larvae or adults?
4 What would you recommend the farmer to do based on these results?
5 Why do high doses of pesticide lower the quality of a food crop?
6 Make a table showing the advantages and disadvantages of biological
control, compared with chemical control. Use your table to help you decide
whether biological control is worth the extra expense.
© Nuffield Foundation 1996

NUFFIELD BIOLOGY
ACTIVITIES FOR GCSE
Nuffield Science Activities for GCSE
General editor
Mary Whitehouse
Biology editor
Diane Galloway
Biology contributors
Andrew Hunt
John Kearsey
Jean McLean
Grace Monger
Alastair Sandiforth
Paul Spencer
Tim Turvey
Biology safety adviser
Philip Bunyan
The activities in this pack are the 'best of Nuffield Science at Key stage 4' -
selected from Pathways through Science and Nuffield Co-ordinated Sciences,
revised, improved and supplemented to match the new curriculum. They are
cross-referenced in the Nuffield teaching support booklet for double and single
award science from MEG (syllabuses 1794 and 1795), and are also referred to
in the MEG Science: Biology (Nuffield) syllabus (1785).
The activities cover the 1995 Science National Curriculum Programme of Study
at Key stage 4, so they are very useful for any syllabus.
There are corresponding packs for Chemistry and Physics. Each pack contains
128 copiable sheets and accompanying teachers' notes.
ISBN 0 904956 28 8