Food Web

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MAL
Food Chains / Webs
All you ever wanted to know about
things eating each other, and more!
© by Marvin Lowe
25 South 1300 East, Logan, Utah
All Rights Reserved ©
What are your learning objectives from
this presentation of food webs/chains

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MAL
Food Webs/Chains
Learning Objectives
Categorize and identify relationships between organisms
(i.e., producer/consumer/decomposer, Trophic Levels,
predator/prey, symbiosis – mutualism / parasitism /
commensalism) and provide examples of each.
Use models to trace the flow of energy and nutrients in food
chains and food webs.
List the five (5) rules you should follow when interpreting
and organizing a food web.
Construct the energy pyramid for a given food web starting
with a specific amount of energy measured in calories at
any particular level of the food web.
List and describe five (5) primary resources that organisms
compete for in an ecosystem.

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MAL
Terms to Know
• Autotroph
• Calories
• Carnivore
• Chemotroph
• Commensalism
• Competition
• Consumer
• Copavore
• Crowding
• Decomposer
• Ecosystem
• Energy Pyramid
• Environment
• Food Chain
• Food Web
• Fructivore
• Habitat
• Hemovore
• Herbivore
• Heterotrophic
• Host
• Mate
• Mutualism
• Niche
• Omnivore
• Organism
• Parasitism
• Predator
• Predation
• Prey
• Primary Consumer
• Producer
• Scavenger
• Secondary Consumer
• Shelter
• Stress
• Symbiosis
• Territory
• Tertiary Consumer

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Food Chains
• A food chain is a
simple way to look at
how matter and
energy flow through a
specific part of an
ecosystem.
• Organisms don’t
generally eat only one
thing, so the picture is
never this simple.

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Food Webs
• A Food Web is a model
used to represent energy
and matter flowing
through an ecosystem.
• Food webs look
complicated because
they are complicated.
Real life is even worse.
• What is missing from this
food web
• Phytoplankton Zooplankton
Phytoplankton

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Food Web Rules
1. List all the organisms you’re studying.
2. Answer the question for each organism:
“What eats what”
3. Arrange the organisms in a logical manner,
with the top predators (Tertiary Consumers)
at the top of your chart, and the Producers
at the bottom of your chart.
4. Link the organisms together using arrows that
show the direction in which the ENERGY and
Matter flow.
5. Link the Decomposers to EVERYTHING!

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Producers, Consumers, and
Decomposers
• A producer uses an energy source (usually
sunlight) to organize food out of raw materials.
(Autotroph)
• A consumer is an organism that can’t make it’s
own food (so they eat producers or other
consumers or both). (Chemotroph)
• A decomposer is an organism that breaks dead
organisms down into simple materials again—
(Nature’s recycling system).

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Consumer Feeding Levels
• A Primary
Consumer eats
Producers.
• Primary
Consumers are
Herbivores and/or
Fructivore.

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Consumer Feeding Levels
• A Secondary Consumer
eats Primary
Consumers.
• Secondary Consumers
are Carnivores.

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Consumer Feeding Levels
• A Tertiary Consumer
(Third Level) eats
organisms that eat other
organisms that eat
producers.
• Some organisms can be
First, Second, and Third
Level Consumers.
(Heterotrophic)
• What level of consumer
are people

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The Energy Pyramid
• We talked in class about how you have
less energy as you move from Producers
to Primary Consumers, even less as you
go from Primary Consumers to Secondary
Consumers, and so on.
• At every level, energy is used up by
organisms and lost to the environment in
the form of heat energy.
• How much energy moves from one level to
the next

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Primary
Consumers
Producers
Tertiary
Consumer
(10 kcal) (0.1%)
Secondary
Consumers
(100 kcal) (1%)
(1,000 kcal) (10%)
(10,000 kcal) (100%)
The Energy Pyramid
• Only Ten Percent!
(10%)
• If you have 10,000
kilocalories available
at the Producer level,
you have 1,000
kilocalories available
at the Primary
Consumer Level, 100
kilocalories at the
Secondary Consumer
level, and 10
kilocalories left at the
tertiary Consumer
level.

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The Energy Pyramid
Decreasing
number of
organisms
Decreasing
Energy
Increasing
number of
organisms
Increasing
Energy
This is a direct relationship

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Resources
• Energy is one resource organisms need to
live. They compete to get energy (food).
• Organisms also compete for territory,
mates, shelter, and water.
• A niche is an organism’s place in the
ecosystem. It’s basically a way to make
sure that two organisms don’t have to fight
too hard for the same food resource.

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Species Interactions
Organisms interact in Five general ways:
• Symbiotic Relationships (Symbiosis)
Mutualism/Parasitism/Commensalism
• Predation
• Competition
• Crowding
• Stress

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Mutualism (+/+)
(Symbiosis)
• In Mutualism, both
organisms involved
benefit from the
interaction.
• Turkey Vultures find
the meat, King
Vultures rip open the
carcass, and
everyone has a feast.

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Parasitism (+/-)
(Symbiosis)
• Parasitism is a special
type of Predation.
• Parasites live on or in a
host organism and steal
resources from that
organism.
• It isn’t usually wise for a
parasite to kill it’s host.

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Commensalism (+/0)
(Symbiosis)
• In commensalism one of
the organism benefits
and the other neither
benefits or is harmed by
the relationship.

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Predation (+/-)
NOT SYMBIOSIS
• One species benefits
• The other is hunted, killed and
eaten.
• Predation is beneficial to prey
species because it removes the
old, sick, weak, members of the
population. The fact that
sometimes the very young
members of the population are
removed is not a benefit.
• Even though it can benefit the
prey population, I still doubt this
Zebra really wanted to be eaten.

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Competition (-/-)
NOT SYMBIOSIS
• Competition is not a form of
symbiosis but has a (-/-)
relationship between the
organisms involved.
• Competition is when two or more
organisms are competing for the
same resource.
• This is avoided by specializing into
different niches.
• Cooper’s Hawks hunt birds, Red-
Tailed Hawks hunt rodents while
living in the same eco-system.

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Competition Within Species
Members of the same species can compete
for the same resources such as territory,
mates, shelter, water, and food.
Any kind of competition either inter or intra
species will cause the elimination of the old,
sick, weak, and not a benefit, sometimes the
very young members of some populations of
organisms.

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Terms to Know
• Calories
• Carnivore
• Commensalism
• Competition
• Coprovore
• Decomposer
• Ecosystem
• Energy Pyramid
• Environment
• Food Chain
• Food Web
• Fructivore
• Habitat
• Hemovore
• Herbivore
• Mutualism
• Mate
• Niche
• Organism
• Omnivore
• Parasitism
• Predator
• Predation
• Prey
• Primary Consumer
• Producer
• Scavenger
• Secondary Consumer
• Symbiosis
• Territory
• Tertiary Consumer

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Food Web/Food Chain objectives
Review
● Categorize the relationships between organisms
(i.e., producer/consumer/decomposer, trophic levels,
predator/prey, symbiosis – mutualism / parasitism /
commensalism) and provide examples of each.
● Use models to trace the flow of energy in food chains
and food webs.
● List the rules you should follow when interpreting
and organizing a food web.
● Construct the energy pyramid for a given food web
starting with a specific amount of energy measured
in calories at any particular level of the food web.
● List and describe four (4) primary resources that
organisms compete for in an ecosystem.

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Glossary
A - C D - E F - G H - L M - O P - R S - Z
Select the above letter category in
which the word you are looking for
would be found.

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Glossary (A – C)
Autotrophic – Any organism that makes its own food using
sunlight as the energy source. (algae, plants and some bacteria)
Calories – A metric unit used to measure the energy needed to
raise the temperature of one gram of water by one degree
Celsius. The energy gained by respiration of food is measured
in calories.
Carnivore – An animal that eats only other animals. Lions are
carnivores.
Chemotrophic – Any organism that can not produce its own
food but must eat producers or other consumers.
Commensalism – A symbiotic relationship between two
organisms of different species in which one derives some
benefit while the other is unaffected. A birds nest in a tree is
an example of commensalism.

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Glossary (C – C)
Competition – The simultaneous demand by two or more
organisms for limited environmental recourses. Mice and
grasshoppers are in competition for grass to eat.
Consumer – Any organism that must eat producers or other
consumers.
Coprovore – An animal that eats feces of animals. Dogs and
dung beetles are coprovores.
Crowding – The number and closeness of all of the various
organisms in an ecosystem.

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Glossary (D – E)
Decomposer – An organism that breaks down large chemical
molecules from dead organisms into small chemical molecules
and returns important materials to the soil and water. Fungi,
earth worms, and some bacteria are decomposers.
Ecosystem – All of the living and non living things that interact
in a specific area. The Cache Valley wet lands might be
considered an ecosystem.
Energy Pyramid – A diagram that show the amount of energy
that moves from one feeding level to another in a food chain.
The rule of thumb in an energy pyramid is that 90% of the
incoming energy is used for life function leaving 10% that is
passed on to the next level of the food chain.
Environment – A combination of the abiotic and biotic factors
and there effect on each other in an ecosystem.

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Glossary (F – G)
Food Chain – A series of events in which one organism eats
another. Producers are always the first thing in a food
chain.
Food Web – The pattern of overlapping food chains in an
ecosystem. That food web of the organisms in the Cache
Valley wet lands.
Fructivore – An organism that eats mostly fruit. Fruit Bats,
and some monkeys are fructivores.

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Glossary (H – L)
Habitat – The place where an organism lives and provides the
things the organism needs. The place an organism lives is its
habitat.
Hemovore – An organism that eats blood predominantly.
Mesquites are hemovores.
Herbivore – An organism that eats predominantly plant
material. Deer cows and horses are all herbivores.
Heterotrophic – Consumers that can eat at more than one
trophic level.

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Glossary (M – O)
Mate – The sexual partner of an organism. The mother of
those puppies is that dogs mate.
Mutualism – A type of symbiosis in which both organisms
benefit from living with each other. The relationship between
the long eared bat and the saguaro cactus is mutualism.
Niche – An organisms role in an ecosystem, how it makes its
living. Each organism fills a specific niche.
Omnivore – Can eat almost any kind of food. Humans and
bears are omnivores.
Organism – A living thing. All organisms need to eat food.

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Glossary (P - R)
Parasitism – A relationship in which one organism lives in or
on another organism and harms it. The relationship between
mosquitoes and human is parasitism.
Predator – A carnivore that hunts and kills other animals for
food and has adaptations that help it capture the animals it
preys upon. One of the predators of a zebra is a lion.
Predation – The act of being a predator. Barn owls practice
predation of voles.
Prey – An animal that a predator feeds upon. Grasshoppers
are prey of snakes.
Primary consumer – An organism that eats producers
(autotrophs). Rabbits are primary consumers.
Producer – An organism that can make its own food. Plants
and some bacteria are producers.

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Glossary (S – Z)
Scavenger – A carnivore that feeds on the bodies of dead or
nearly dead organisms. Vultures are scavengers.
Secondary consumer – An organism that eats primary
consumers. When a snake eats a cricket it is a secondary
consumer.
Symbiosis – A close relationship between two organisms in
which at least one organism benefits. There are three type of
symbiosis; mutualism, parasitism, and commensalism.
Territory – An area that is occupied and defended by an
animal or group of animals. A wolf marks its territory by
urinating around the outer edge of the territory.
Tertiary consumer – An organism that eats secondary
consumers. When a hawk eats a small bird that has eaten a
grasshopper it is a tertiary consumer.

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Terms to Know
• Calories
• Carnivore
• Commensalism
• Competition
• Consumer
• Coprovore
• Decomposer
• Ecosystem
• Energy Pyramid
• Environment
• Food Chain
• Food Web
• Fructivore
• Habitat
• Hemovore
• Herbivore
• Mate
• Mutualism
• Niche
• Omnivore
• Organism
• Parasitism
• Predator
• Predation
• Prey
• Primary Consumer
• Producer
• Scavenger
• Secondary Consumer
• Symbiosis
• Territory
• Tertiary Consumer