Food Chains
Outcome:
4-1-10: Recognize that the food chain is a system in which some energy from the
Sun is transferred eventually to animals.
Materials:
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writing utensil
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colouring utensils
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scissors
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string
Teacher’s Instructions:
1. Make a class set of page 3.
2. Ask students to make their own food chains using the shapes provided on page 3.
They will choose appropriate examples for each level of the food chain (e.g. a
bear would not be a producer or a first level consumer). Make sure that at least
one Manitoba fish species is included in their food chains.
3. Ask students to draw and label their examples inside the shapes, then cut them
out.
4. Attach the shapes with string, beginning with the producer. Display the completed
food chains in the classroom.
Adaptations/Modifications:
Students can cut out pictures from magazines instead of drawing their own pictures.
Teacher Background Information:
A food chain is the transfer of food energy from plants (producers) through a series
of animals (consumers), each being eaten by another animal. Food energy supplied
from plants ultimately comes from the Sun.
Green plants are producers - they make their own food from simple organic
substances. In an aquatic ecosystem, producers include algae or phytoplankton,
and aquatic plants.
Consumers are organisms which require complex organic compounds for food.
They cannot make their own food but must get their energy by preying on other
organisms. An animal that eats only plants is called a herbivore. Snails feed on
living algae which covers submerged plants. Zooplankton (tiny aquatic organisms
that feed on phytoplankton), some insect larvae (e.g. chironomids), and some
leeches are herbivores.
Continued on page 2
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Teacher Background Information (Cont’d.):
An animal that eats only other animals is called a carnivore. Some leeches are
carnivorous, eating insect larvae and other small invertebrates. Goldeye are
carnivores, eating primarily surface and aquatic insects, crustaceans, and sometimes
small fish. Walleye and northern pike are also carnivores, but we refer to them more
specifically as piscivores, because they primarily eat other fish. Walleye will also eat
crayfish, leeches and aquatic invertebrates. Pike eat frogs and crayfish, and have
been known to even go after mice, muskrats and ducklings, depending on their size.
An animal that eats both plants and animals is called an omnivore. Humans are
omnivores; we eat plants and animals, including fish. (We often forget that we are the
top predator in many aquatic food chains!) Some insect larvae (e.g. mayflies,
caddisflies) are omnivorous. Freshwater mussels (clams) are omnivorous; they are
filter-feeders and filter phytoplankton and zooplankton out of the water for their food.
Catfish and sturgeon are omnivorous. Catfish eat mayflies, caddisflies, chironomids,
molluscs (clams and snails), crayfish, green algae, larger plants, tree seeds, and fish.
Sturgeon eat a variety of things, depending on what they can find on the river bottom,
including plants, crayfish, molluscs, insect larvae, nematodes, leeches, amphipods,
and decapods.
Decomposers are organisms that convert dead organic materials into inorganic
materials, i.e. plants or animals that feed on dead material causing its mechanical or
chemical breakdown (e.g. bacteria, fungi).
Scavengers are animals that eat food that has already been killed. Rather than kill
their own food, scavengers rely on other animals to kill for them, or they rely on finding
dead or decomposing matter to eat. Crayfish are usually considered to be scavengers;
they are also omnivorous although they prefer aquatic vegetation. Some leeches are
also scavengers.
Most animals eat and are eaten by several different organisms. A food chain is only
one path that energy can take. If you trace all the paths, you have a food web. Food
webs consist of intertwining and overlapping food chains.
In aquatic food chains, many of the organisms that fish consume, eat the same things.
Some small fish (minnows), such as shiners, will eat zooplankton and amphipods.
Other small fish, such as sticklebacks, eat insect larvae, which in turn may eat
zooplankton, phytoplankton (tiny plant organisms), or other plant material. Freshwater
mussels, or clams, also consume phytoplankton and zooplankton, which they filter out
of the water. Thus, minnows, insect larvae and clams all eat the same food even
though they feed in different ways and are at different levels in the food chain.
Leeches are a particularly interesting aquatic organism in that they eat many different
things; some species are herbivorous, some are carnivorous, and some are
scavengers. Collectively known as "bloodsuckers" to most of us, very few leech
species actually take blood from warm-blooded animals.
Like some species of leeches, crayfish are also usually considered to be scavengers;
although omnivorous, crayfish prefer aquatic vegetation.
We should not forget that for most of our Manitoba fish species, humans are a major
predator, and are actually at the top of most aquatic food chains. In fact, humans are
the only predators of adult sturgeon, which have no natural enemies because of their
size and heavy "armour".
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Food Chains
example:
Using one or more Manitoba fish species, draw on,
label and cut out the shapes. Join them together with
string to make a food chain.
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