Transfer of Energy in
Ecosystems
(Food Webs/Food Chains)
Enviro2Go
6212, 6213, 6214,6222
Objectives:
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You will be able to:
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Explain how energy flows through an ecosystem in
terms of trophic levels.
Explain how trophic levels and food chains are
related.
Explain how the amount of energy changes as the
trophic levels increase.
Describe the role of each organism in a food chain or
food web
Describe similarities and differences between food
chains and food webs.
Describe and explain and organisms niche.
Describe an energy & biomass pyramid.
Key Vocabulary
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Trophic level
Consumer
Heterotroph
Producer
Autotroph
Herbivore
Omnivore
Carnivore
Scavenger
Decomposer
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Food chain
Food web
Biomass pyramid
Phytoplankton
Zooplankton
Krill
Niche
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Energy pyramid
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The Sun
The sun is the ultimate source of energy. The sun
provides energy for photosynthesis, which allows plants
to grow. Plants are important for a number of different
reasons. Plants provide animals with the food and
oxygen necessary for life.
Niche
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Every organism has a niche.
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A niche is described as the organisms’ role in the
ecosystem.
The role is defined based on what it needs to survive;
what it eats.
Example: Squirrels are often called
“acorn gatherers” because one of their
main sources of food is acorns. This
describes their niche.
Producers
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Plants get their energy from the sun and use it to
make glucose (sugar) during photosynthesis.
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Because plants make their own food (glucose)
they are called producers.
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Another name for a producer is an autotroph.
C0nsumers
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Since animals cannot make glucose they must eat
other organisms to get energy.
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Any organism that eats to get energy is called a
consumer.
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Another name for a consumer is a heterotroph.
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There are many different consumers. Consumers
are titled based on what they eat.
Types of Consumers
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Herbivores: only eat plants
This deer is a herbivore because
it eats plant material.
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Omnivores: eat plant & meat material
This bear is a omnivore because it
eats both plant and animal material.
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Carnivores: only eat meat
This polar bear is a
carnivore because it
feeds of off other
animals.
More Types of Consumers
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Scavengers: eat off of dead organisms
These vultures are feeding off of a
dead elephant making them
scavengers.
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Decomposers: break down dead or decaying material
down old
This fungi is an example of a
decomposer because it is breaking
plant material.
The Importance of Decomposers
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Decomposers break dead
things down so that they
can be reused by plants
and other organisms.
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If we did not have
decomposers, ALL the
things that have ever died
since the beginning of
time would still be lying
around on Earth!
REMEMBER THIS!!!
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Plants make their own food during
photosynthesis. Plants use energy from
the sun to make glucose (sugar).
Therefore, plants are called producers.
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Animals eat plants to get energy because
they cannot make their own food.
Animals are called consumers.
Consumers can be herbivores,
omnivores, carnivores, or scavengers
based on what they eat.
Questions???
1.
What is the ultimate source of energy?
2.
What is a niche?
3.
An organism that makes its’ own food could be
called a ___________, ___________ or
___________.
4.
An organism that only eats meat is called a
___________.
Food Chains
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A food chain shows the flow of energy from one
organism to the next.
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As an organism eats another organism it receives
energy. Therefore, consumers are found after
producers in a food chain.
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The arrows
in a food chain point in the
direction that the energy is flowing.
Food Chains
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In this marine (aquatic) food chain,
the phytoplankton is the producer. That
means the phytoplankton makes its’
own food during photosynthesis.
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The zooplankton is the herbivore
because it eats the phytoplankton
(the plant).
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The fish and whales are all carnivores
because they eat only other animals (meat).
Food Chains
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Consumers can also be classified as primary,
secondary, tertiary or quaternary consumers.
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The zooplankton is the primary consumer because it is
the first consumer. It eats the producer.
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The small fish are the secondary consumers because
they eat the primary consumer.
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The large fish is the tertiary consumer because it eats
the secondary consumer.
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The whale is the quaternary consumer because it eats
the tertiary consumer.
REMEMBER THIS!!!
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Food chains show the flow of energy in
an ecosystem.
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Organisms eat other organisms to get
energy.
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The arrows in a food chain show the
direction that the energy is moving.
Questions???
5.
What is/are the producer(s) in this
terrestrial food chain?
6.
What is/are the herbivore(s) in this
terrestrial food chain?
7.
What is/are the carnivore(s) in this
terrestrial food chain?
Create Your Own Food Chain
Visit the following website to create your
own food chain!
Make Your Own Food Chain!
Food Webs
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Food webs are multiple food chains all
interconnected.
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Food webs show most of the possible foods an
organism can eat in that ecosystem.
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Food webs can be terrestrial (land based) or
aquatic (water based).
Terrestrial Food Web
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The vegetation is the producer
in this food web.
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The insects, mice, rabbits and
deer are all herbivores. They are
also considered primary
consumers.
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The snake, frogs, foxes, and
cougar are all carnivores. They
are also considered secondary
consumers.
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The fox can also be considered a
tertiary consumer when they eat
the frog. This is because the frog
is a secondary consumer, & the
insect is the primary consumer.
Questions???
8. What is the
producer in this
terrestrial food
web?
9. What is/are the
primary
consumer(s) in
this food web?
11. Are there any omnivores in this
food web? If so, what are they?
10. Would the owl
be a herbivore,
omnivore or
carnivore?
Aquatic Food Webs
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Ocean food webs begin with
phytoplankton. Phytoplankton
are small aquatic plants found
near the ocean’s surface.
Phytoplankton is eaten by
zooplankton; tiny animals.
Krill is a common example of
zooplankton. Krill are tiny
shrimp-like creatures that eat
both phytoplankton and
zooplankton.
Watch This Video on Krill!
- Krill
Changes in Food Webs
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When the population of one
organism in a food web changes,
all other organisms can be
affected.
For example in this food web, if
the population of the zooplankton
decreased:
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The phytoplankton would increase
because nothing would be eating it.
The migrating midwater fishes
would decrease because they would
have no food. This would result in
competition and a decrease in the
other fish due to a lack of food.
- Krill
Changes in Food Webs
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Use this link to see the affects of changing
populations within an ecosystem.
Changes in Food Webs!
Questions???
Using the information from the video you just
watched, answer the following questions.
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What would happen to the Great Blue Heron
population if the algae decreased?
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What would happen to the perch if the bass
population increased?
Energy Pyramids
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An energy pyramid shows the energy flow from one
organism to the next. Each level in an energy pyramid is
called a trophic level.
coyote
fox
rabbit
grass
This level contains
carnivores.
Trophic Level 4
Trophic Level 3
This level contains
omnivores or carnivores.
Trophic Level 2
Trophic Level 1
This level always contains producers.
This level contains
herbivores and
omnivores.
Energy Pyramids
 As
energy moves from one trophic level to
the next, energy is lost. This is because
organisms use energy to live, so only a little
bit of energy goes to the animal that eats it.
 Only
10% of the energy is passed on from
one trophic level to the next. That means
organisms use 90% of the energy they
make/consume for their own activity.
Energy Pyramid
coyotes
fox
rabbit
grass
Trophic Level 4
1 unit of energy
Trophic Level 3
10 units of energy
Trophic Level 2
Trophic Level 1
100 units of energy
1000 units of
energy
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In this energy pyramid the grass has 1000 units of energy. It
will use 90% of the energy and pass 10% on to the rabbit. This
continues through the food chain.
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Since the energy decreases, the amount of animals high up on the
food chain also decrease because they have to eat more to get
enough energy to live. Therefore, there will always be more producers
than consumers.
REMEMBER THIS!!!
As trophic levels increase, the amount of
energy they receive decreases.
Questions???
14.
Each level of an energy pyramid is called a _______
_______.
15.
Would you find a producer or consumer at the first trophic
level?
16.
Where is the most available energy, trophic level 1 or trophic
level 4? Why?
17.
What percent of energy moves from one organism to the
next?
Biomass Pyramids
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Biomass is the dry weight of plants and animals.
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Because energy decreases from one trophic level,
there are less animals at high trophic levels of a
food chain.
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So, only about 10% of the total biomass moves
on from one trophic level to the next.
Review
Visit the following website to review food chains,
food webs, energy pyramids and biomass
pyramids!
Quick Review!
Summary
Food chains show the flow of energy from one
organism to another. A food web shows the
multiple feeding relationships that can occur.
 Organisms eat other organisms to get energy.
However only 10% of the energy gets passed on.
 An energy pyramid shows the loss of energy
from one trophic level to the next. Remember,
only 10% of the energy moves from one level to
the next!
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Test Yourself:
True or False
____ 1. Producers are animals.
____ 2. A carnivore eats only plants.
____ 3. Zooplankton is food for larger fish.
____ 4. Decomposers are a special kind of
consumer.
____ 5. The sun is the ultimate source of energy for
ecosystems.
____ 6. A niche is where an organism lives.
____ 7. A niche tells us what an organism eats and
sleeps, among other things.
Test Yourself:
Matching
____ 1. trophic level
a) The dry weight of organisms in a food chain
____ 2. energy pyramid
b) Eats only producers
____ 3. producer
c) Breaks down dead, decaying matter
____ 4. consumer
d) Eats only consumers
____ 5. herbivore
e) Makes their own food from the sun
____ 6. omnivore
f) Eats dead organisms
____ 7. carnivore
g) Eats both producers and consumers
____ 8. scavenger
h) Feeding levels in a food chain
____ 9. decomposer
i) Must obtain energy by eating other organisms
____ 10. biomass
j) Diagram that shows the amount of energy
transferred between organisms
Test Yourself :
Fill in the Blank
decomposers
trophic
1.
that
food chain
herbivores
food web
energy
The term ____________________ is given to the bacteria
break down dead tissue.
2.
In an ecosystem, ____________________ decreases at each
higher trophic level.
3.
Animals known as ____________________ eat only
primary producers.
4.
A path of energy through the trophic levels of an ecosystem is
called a(n) ____________________ ____________________.
5.
The interrelated food chains in an ecosystem are called a(n)
____________________ ____________________.
Test Yourself:
Short Answer
1.
The grocery store has a section in it called the Produce
section. What types of things do you find in that
section?
2.
In a food chain, where are the producers always found?
3.
Why are consumers always listed after producers in a
food chain?
Test Yourself:
Short Answer
4.
What is the difference between a food chain and a food
web?
5.
Why are decomposers necessary for the continuation of
life on Earth?