10.2 · Roles Are About Getting Energy

From Ohio 5th Grade Science Power Workbook · Chapter 10 · Lesson 10.2.

Big idea: Organisms are sorted into roles by HOW they get their energy: producers, consumers and decomposers.

Learning goals: Name the three roles organisms play in an ecosystem

Sort organisms by how they get energy

Explain why producers are the foundation

Three roles, one question

To work out an organism's role, ask one question: how does it get its energy?

A producer makes its own food using the sun's energy. A consumer eats other living things. A decomposer breaks down dead plants and animals.

Producers come first

Producers are the foundation of the food web. Every consumer eats either a producer or something that ate one.

Take the producers out and everything else runs out of food. Nothing is left to bring energy into the ecosystem.

Worked examples

Question: A student is given three Ohio organisms: pond algae, a minnow and an earthworm. Sort them by role and explain each choice.

Steps: Ask how the algae get energy. They use sunlight to make their own food, so they are producers.

Ask how the minnow gets energy. It eats other living things, so it is a consumer.

Ask how the earthworm gets energy. It breaks down dead plant material, so it is a decomposer.

Answer: Algae are producers, the minnow is a consumer and the earthworm is a decomposer. Each role is decided by how the organism gets its energy.

Common mistakes

Size does not decide the role

An oak tree is enormous and a mayfly is tiny, but the oak is a producer and the mayfly is a consumer.

Role has nothing to do with size, or with whether an organism moves. It is only about how the organism gets its energy.

Check your thinking: Ask the one question every time: how does it get its energy? Never how big it is.

Remember

Make it, eat it, or break it down

Three roles, three verbs. Make your own food — producer. Eat other living things — consumer. Break down dead things — decomposer.

Practice tip

Remember: One question decides the role.

Tip: Whenever Ohio asks you to classify an organism, ask how it gets its energy. Makes its own food, eats living things, or breaks down dead things — that is the whole system.

Written practice

Explain why an oak tree and pond algae have the same role even though one is huge and one is microscopic.

Sample response: Both are producers. Role has nothing to do with size — it depends only on how an organism gets its energy. The oak tree and the algae both use the sun's energy to make their own food, so they play the same role in the ecosystem.

Scoring guide: 1 point: says both are producers.

1 point: explains that role depends on how an organism gets energy, and both make their own food using the sun's energy.

Ohio's classification is entirely about how energy is acquired.