Grade by Grade
B. Life Systems · Habitats and Communities

Food Chains: Producers, Consumers and Decomposers

B2.3 A1.1 A1.5About 40 minutes
Learning goals
  • I can explain that energy in a food chain starts with the Sun.
  • I can draw a food chain with arrows pointing the correct way.
  • I can classify organisms as producers, consumers or decomposers.
  • I can explain why decomposers are important to every habitat.

Words to know

food chain
A path that shows who eats whom, and how energy passes from one living thing to the next.
energy
What living things need to move, grow and stay alive. It comes from food, and the energy in food starts with the Sun.
producer
An organism that makes its own food using sunlight. Plants and algae are producers.
consumer
An organism that gets energy by eating other organisms. All animals are consumers.
decomposer
An organism that breaks down dead plants and animals and returns nutrients to the soil, like fungi and bacteria. Worms help too.
top predator
A consumer at the end of a food chain that is not usually eaten by other animals.

Remember from Grade 3

In Grade 3 you learned that plants make food from sunlight (photosynthesis) and that animals depend on plants. You saw simple food chains like clover → rabbit → fox. Now let's look at food chains like a scientist and give each living thing a job title.

Where does your energy come from?

You ate breakfast this morning, so you have energy to run and think. But where did the energy in your breakfast come from?

Say you ate toast. Toast is made from wheat. The wheat plant got its energy from... the Sun! Almost all the energy in every food chain on Earth starts with the Sun.

A field of ripe golden wheat under a blue summer sky.
Wheat plants are producers. They capture energy from the Sun, and that energy ends up in your toast. AI-generated image

Reading a food chain

A food chain shows how energy passes from one organism to the next when one eats another.

The arrow points toward the eater. You can read an arrow as "is eaten by" or "gives energy to".

So grass → grasshopper means "grass is eaten by the grasshopper".

grassgrass-hopperfrogsnakehawkEach arrow means "is eaten by". Energy moves along the arrows.
A meadow food chain: grass → grasshopper → frog → snake → hawk.

Three job titles

  1. Producers make their own food using sunlight. Plants (grass, maple trees, cattails) and algae are producers. Every food chain starts with a producer.
  2. Consumers get energy by eating other organisms. All animals are consumers. The first animal in the chain, which eats the producer, is a plant-eater. Animals after that eat other animals. The last one is often a top predator.
  3. Decomposers break down dead plants and animals, and animal waste. Fungi (like mushrooms) and bacteria are decomposers. Earthworms, millipedes and pill bugs help break things down too.

Decomposers are not usually drawn in the chain, but they work at every link: when any organism dies, decomposers break it down.

dead plantsand animalsdecom-posersnutrientsin the soilplantsgrowDecomposers recycle nutrients back into the soil.
Decomposers turn dead things into nutrients that plants use to grow.
OrganismJobHow it gets energy
grassproducermakes its own food from sunlight
grasshopperconsumer (eats plants)eats grass
frogconsumereats grasshoppers and other insects
garter snakeconsumereats frogs, worms and other small animals
red-tailed hawkconsumer (top predator)eats snakes, mice and other animals
mushroom (fungus)decomposerbreaks down dead plants and animals
Classifying the members of a meadow community.
Worked example

Let's build a pond food chain

Make a food chain with: great blue heron, algae, yellow perch, mayfly nymph (a young mayfly that lives in water). Then classify each one.

  1. Find the producer: algae make their own food from sunlight. Start there.
  2. Who eats algae? The mayfly nymph. Algae → mayfly nymph.
  3. Who eats mayfly nymphs? The yellow perch (a fish).
  4. Who eats perch? The great blue heron.
  5. Classify: algae = producer; mayfly nymph, perch and heron = consumers; the heron is the top predator here.

algae → mayfly nymph → yellow perch → great blue heron. When any of them dies, decomposers (bacteria and fungi in the pond mud) break it down.

Worked example

Let's look at an Arctic food chain

Inuit hunters and scientists know the Arctic Ocean well. Build a chain with: ringed seal, algae under the sea ice, polar bear, Arctic cod.

  1. Producer: algae that grow on the underside of the sea ice.
  2. Tiny animals eat the algae, and Arctic cod eat those tiny animals (we can skip a step to keep it short).
  3. Ringed seals eat Arctic cod.
  4. Polar bears hunt ringed seals.

algae → (tiny animals) → Arctic cod → ringed seal → polar bear. The polar bear is the top predator.

Just for fun

Q: Why do mushrooms get invited to every party?

A: Because they're such fun-gi! (They're also great decomposers.)

Hands-on activity

Food chain mobile

You need: 5 paper plates or paper circles, a coat hanger or stick, string, tape, pencil crayons.

  1. Choose an Ontario habitat: a meadow, a forest, a pond or a lake.
  2. Research a food chain of 4 or 5 organisms from that habitat. Start with a producer.
  3. Draw one organism on each circle. On the back, write producer, consumer or decomposer and what it eats.
  4. Hang the circles from the hanger in order, from the bottom (producer) to the top (top predator). Draw arrows on paper strips pointing toward the eater.
  5. Add a 6th circle with a decomposer (a mushroom or bacteria) and hang it so it touches the whole chain.
  6. Explain your mobile to someone: "The energy starts with the Sun, then..."

Grown-up note: Help with any sharp ends on the hanger.

Your turn

1

Where does the energy in almost every food chain start?

2

What does an arrow in a food chain mean?

3

What is a producer? Give two examples.

4

What is a consumer? Give two examples.

5

What is a decomposer? Give two examples.

6

Put in order: frog, hawk, grass, snake, grasshopper.

7

Which organism always comes first in a food chain?

More practice: warm-up

1

Is a maple tree a producer or a consumer?

2

Is a moose a producer or a consumer?

3

Is a mushroom a producer or a decomposer?

4

In clover → rabbit, which way does the energy go?

5

What is the top predator in grass → grasshopper → frog → snake → hawk?

More practice: on your own

1

Fix this food chain: fox → mouse → seeds.

2

Make a forest food chain with: chickadee, maple leaves, Cooper's hawk, caterpillar.

3

Why do all food chains need a producer?

4

What would happen in a forest if there were no decomposers?

5

A garter snake eats a frog. Which one is the predator and which one is the prey?

Challenge

1

Trace the energy in a hawk's meal back to the Sun, using the meadow food chain.

2

Are earthworms consumers or decomposers? Explain why scientists might say both.

3

Write a food chain that includes you and has at least three links. Label each part.

Check your understanding

Quiz

1.

Which organism is a producer?

2.

In a food chain, the arrow points...

3.

Which is a decomposer?

4.

Which food chain is written correctly?

5.

Where does the energy in a food chain first come from?

6.

A consumer is an organism that...

7.

Without decomposers, a forest would...

For parents and teachers

This lesson classifies organisms as producers, consumers and decomposers and practises drawing food chains.

Common difficulties:

  • Arrow direction. Children often point arrows toward the food ("the fox goes to the mouse"). Practise saying "is eaten by" for each arrow.
  • Forgetting that a food chain must start with a producer.
  • Thinking decomposers are "gross" and unimportant. Stress that without them nutrients would not be recycled.

At home: At dinner, trace one food back to the Sun together.