Chapter 15

Chapter 15
Section 1
The Theory of Evolution
Natural Selection and the Evidence of Evolution
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A. Charles Darwin & Natural Selection
• To understand many of the fields of biology you must understand evolution.
1. ______________________________________________
a. 1831, age 21, Darwin took a job as a naturalist on the HMS Beagle. This
was a ship whose purpose was to chart and map South America and the
South Pacific.
b. His job was to collect, study and store biological specimens collected.
c. _________________________________________
i. Small group of islands about 100 km from S.A.
ii. Darwin studied reptiles, insects, birds and flowering plants unique to the
islands, but similar to the rest of the world.
iii. He saw differences between the islands themselves
d. England
i. When Darwin finished his 5 yr voyage he returned to England and
studied his collections and conducted experiments.
ii. He decided from his research that a “Struggle for Existence” occurred
and only those best suited survived.
a. _____________ d. __________________
b. _____________ e. __________________
c. _____________
iii. Darwin believed only the strongest individuals would survive and
reproduce.
iv. Pigeon Experiments showed Darwin that pigeons with desirable
characteristics would survive and pass on their traits.
v. ________________________ – when a breeder selects the desired
traits and breeds for those traits
e. Natural Selection
i. This was Darwin’s Theory
ii. ___________________________ – is a mechanism for change in
populations that occurs when an organism with the desired traits for
environment, survival, reproduction and then are able to pass these
traits to the next generation – known as “Survival of the Fittest”
iii. Humans - Eating
a. ______________________________
b. ______________________________
c. ______________________________
d. ______________________________
iv. Birds – Drinking
a. Only had small holes in the ground to drink out of
b. Only birds with beaks that fit in the holes will survive and live
to reproduce

v.1850’s – On the Origin of Species
a. Convinced many scientists of evolution
b. Came under intense fire from the church
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B. Natural Selection and Adaptations
1. __________________________________
a. Mole Rats
i. At one time they live above ground
ii. They had characteristics of the African Rock Rat and over time they
developed large teeth and claws. This allowed the mole rats to dig
deeper holes to get away from predators. The mole rats with the
adaptations survived and then passed on their traits.
b. Many animals develop structural adaptations to better survive
c. Structural adaptations may begin but take years and years to develop
d. ________________________________
i. Use to have white moths but the industrial revolution caused pollution.
The white moths would get eaten very quickly on the tress. The moths
that were darker did better and over time they survive and pass on the
trait to their offspring.
2. Physiological Adaptations
a. 50 years ago Penicillin was discovered and used to kill many of the
bacteria that plagued people.
b. Scientists believe the bacteria have adapted and therefore this is why
penicillin is not as effective.
c. Other Ex: Weeds & Insects
C. Evidence of Evolution
1. __________________________________
a. Fossils help to give a history of many organisms
b. There are pieces missing and scientists hypothesize about these gaps; so
every step in evolution is not exact
2. ____________________________________
a. ______________________________ – structures having a common
evolutionary origin; They have a similar structure and function but this
does not mean the organisms themselves are related.
i. Ex: Forearms in bats and humans
b. _____________________________– structures without a common
evolutionary origin that are similar in structure but not in function; This can
be used to indicate evolutionary relationships but do show evidence.
i. Ex: Wing of insect and bird

3. ____________________________________
a. _______________________– any body structure that is reduced in
function in a living organism but many have been used in an ancestor.
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b. These structures become vestigial because of changes in the behavior of
the organism.
c. As the organism continues to pass on traits the organ shrinks in size,
stops functioning and may disappear.
d. Ex: Appendix in Humans
Eyes of Mole Rats
4. _________________________________
a. Embryos all start out somewhat the same.
b. As they form they develop their own structures and functions
c. As a embryo all vertebrates possess some of the same characteristics
i. ___________________________
ii. ___________________________
iii. ___________________________
5. ________________________________
a. If scientists compare DNA of different organisms the DNA can be
compared.
b. Organisms that are closer together in ancestry have more similar DNA
c. Recently, scientists have been using RNA to compare organisms
Chapter 15
Section 2
The Theory of Evolution
Mechanisms of Evolution
A. Population Genetics & Evolution
• When Darwin developed his theory of Natural Selection he did so without considering
the gene and its power.
1. Populations Evolve, Individuals Do Not
a. If an individual organism possesses a phenotype that is not adapted to the
environment it may result in the individual’s inability to successfully
compete.
b. In one lifetime, new features cannot evolve in response to natural selection.
If must occur on the entire population over many generations.
c. ___________________ – the entire collection of genes among a population
d. _________________ – the percentage of a particular allele in a gene pool

e. ________________________ – a population in which the frequency of
alleles does not change from generation to generation
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f. Allelic frequency can change due to natural selection. When this occurs the
genetic equilibrium is disrupted.
2. Changes in Genetic Equilibrium
a. A population in genetic equilibrium is not evolving, it is still. No new traits
are gained or lost.
b. What disrupts genetic equilibrium?
1. _____________________________
2. _____________________________
3. Movement of other organisms into or out of the environment
4. Movement of same species out (gene pool lost) or into the
environment (gene pool gains).
c. The greatest impact on genetic equilibrium is natural selection – it allows
you to lose bad alleles and keep the good ones.
d. __________________ – altercation of allelic frequency by chance events
1. __________________________________________
3. Natural Selection Acts on Variations
a. The result of natural selection is that some members of the population are
more likely to pass on their genes than others.
b. __________________ – selection favoring average individuals, resulting in
the decline of variation in a population
i. Ex: Spiders
a. Average Size Spiders survive the best
b. Too Big – Seen by predators
c. Too Small – Not able to catch enough prey to survive
c. __________________________ – one of the extreme forms of a trait is
favored; can lead to rapid evolution of a population
i. ______________________________
a. A breed of deep tree dwelling insects come into an area
b. Only the woodpeckers with long beaks could get to the
insects to eat.
d. __________________________ – selection favoring individuals at both
extremes of a trait, can lead to the evolution of a new species
i. Limpets (Marine Organisms)
a. Shell color varies from white to dark brown
b. Limpets live on rocks the same color to camouflage
themselves so birds do not prey on them
c. White Limpets – Live on White Rocks
d. Dark Limpets – Live on Dark Rocks
e. Tan Limpets – Neither – They get Eaten

B. The Evolution of Species
• ______________________________ – the evolution of a new species
1. Physical Barriers
a. In the natural world, physical barriers will form and break up the large
populations into smaller ones.
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b. ____________________________ – occurs if a physical barrier separates
a population into groups
1. __________________________
2. __________________________
3. __________________________
4. __________________________
5. __________________________
c. Geographic isolation is one way that a new species can form. Over time
from being separated they adapted to their local environment through
natural selection.
d. Even the gene pools will become different and over time they will change so
much they become a new species
e. Ex: Green Tree Frogs – drought caused them to separate
2. Reproductive Isolation
a. When geographical isolation occurs, gene pools become closed because
no organisms come in or leave.
b. As populations become more distinct reproductive isolation occurs.
c. _____________________n – occurs when formerly interbreeding
organisms are prevented from producing fertile offspring
1. Can occur when genetic material becomes so different that mistakes
occur.
2. Seasonal – mate at different times
3. Chromosomal Abnormalities
a. _______________________ – any species with a multiple of the normal
set of chromosomes.
1. Usually from a mistake in meiosis
2. Fastest form of speciation because it automatically results in
reproductive isolation.
3. When a polyploid individual mates with a normal individual the
zygote has difficulty forming.
4. Usually reserved for plants

4. ________________________ – Can be fast or slow
a. Gradualism – the idea that species originate thru a gradual buildup of new
adaptations
1. Slow and steady
2. Supported by fossil records
b. ____________________________ – speciation occurs in rapid burst
between long periods of stability
1. Requires genetic equilibrium
2. Rapid change in genetics
3. Supported by fossil records
c. Controversy –
1. Many agree that speciation can be fast of slow depending on
conditions in the environment.
5. How does Speciation Occur?
a. Geographical Isolation
b. Reproductive Isolation
c. Chromosomal Abnormalities
C. Patterns of Evolution
• Species Diversify in New Environments
a. ___________________ – process of evolution in which ancestral species
can develop into an array of species that will fit into different niches.
b. Ex: Hawaiian Islands – Honey Creepers
1. Birds are similar in size and shape but differ in colors and beak
shape. The beak shape determines the type of insect the bird will
eat.
c. ____________________________ – evolution in which highly distinctive
species were once similar to an ancestral species
1. Begins when species begin to adapt to different environmental
conditions and change becoming less and less alike
• Distant Species Can Evolve Similar Features
a. _______________________ – evolution of similar traits in distantly
related organisms resulting from adaptations to similar environments.
1. Fish & Dolphins – streamline shape due to water
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