---
title: "Who eats whom?"
subtitle: "Year 7 Biology · Food webs and ecosystems · Lesson 4"
---

# Who eats whom?

**Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}}

> **Key question:** A kookaburra eats lizards, grasshoppers, even small snakes. A food chain can only show one of those meals. How do you show all of them?


:::teacher-note

**In one sentence:** Students construct a food web with arrows in the direction of energy flow and identify producers, consumers and decomposers, including microorganisms (AC9S7U02, node 1, a hinge node).

**Students should be able to say:** I can construct a food web from a list of organisms. I can draw arrows in the direction of energy flow. I can identify producers, consumers and decomposers, including microorganisms.

**Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet.

:::


## Engage


:::keep-together

**In a food web, grass is eaten by a grasshopper. Which way should the arrow point?**

☐ Either way, as long as it's labelled

☐ From the grass to the grasshopper (energy goes into the grasshopper)

☐ From the grasshopper to the grass (the grasshopper eats it)

My prediction, and why:

{{lines-3}}

:::


:::teacher-note

**What happens:** From the grass to the grasshopper. Arrows show the way energy flows: from the food into the eater.

:::


## Explore

Try it on the board in the tutorial. Was your prediction right? What was different?

{{lines-2}}

## Explain: roles in the web


:::keep-together

### Roles

**What is each organism's role in the bush web?**

Groups: Producer, Primary consumer, Secondary consumer, Decomposer

- Grass: {{field-15}}
- Grasshopper: {{field-15}}
- Kangaroo: {{field-15}}
- Lizard: {{field-15}}
- Dingo: {{field-15}}
- Fungi and bacteria: {{field-15}}

:::


:::teacher-note

**Answer:** Grass → Producer; Grasshopper → Primary consumer; Kangaroo → Primary consumer; Lizard → Secondary consumer; Dingo → Secondary consumer; Fungi and bacteria → Decomposer

:::


:::keep-together

### More than one level

**The kookaburra eats both lizards and grasshoppers. What does that make it?**

☐ A secondary consumer when it eats grasshoppers, and a tertiary consumer when it eats lizards

☐ A producer

☐ A primary consumer

:::


:::teacher-note

**Answer:** A secondary consumer when it eats grasshoppers, and a tertiary consumer when it eats lizards

In a web, one animal can feed at more than one level.

:::


:::keep-together

### Decomposers

**Why do decomposers belong in a food web?**

☐ They don't; only animals that hunt belong

☐ They make food from sunlight

☐ They feed on dead organisms and wastes from every level, returning nutrients to the soil

:::


:::teacher-note

**Answer:** They feed on dead organisms and wastes from every level, returning nutrients to the soil

:::


## Mix it up


:::keep-together

**Looking back at the kingdoms: a mushroom grows on a dead log. How does it get its food?**

☐ It absorbs food from the dead log: it is a fungus, so it is a decomposer

☐ It hunts and eats small animals

☐ It makes food from the soil, like a plant

☐ It makes food from sunlight, like a plant

:::


:::teacher-note

**Answer:** It absorbs food from the dead log: it is a fungus, so it is a decomposer

Fungi absorb food from dead material. In a food web that makes them decomposers.

:::


:::typical

## Elaborate: chain or web?


:::keep-together

**The food chain grass → grasshopper → lizard → kookaburra is part of the web. What does the chain leave out?**

☐ The direction of energy flow

☐ Other foods each animal eats, and other animals that eat the same food

☐ Nothing: a chain and a web show the same thing

:::


:::teacher-note

**Answer:** Other foods each animal eats, and other animals that eat the same food

A chain shows one path. A web shows every path, which is why it can predict what happens when one population changes.

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:::wider

## Elaborate: an Antarctic web

Krill eat phytoplankton. Small fish eat krill. Squid eat small fish and krill. Penguins eat small fish, krill and squid. Leopard seals eat penguins and small fish. Bacteria break down dead phytoplankton and dead leopard seals.

:::


## Evaluate: look back

Write one sentence: "At first I thought… Now I think… because…"

**Revision summary**

- A **food web** joins all the food chains in an ecosystem.
- **Arrows point the way energy flows**: from the food to the eater.
- **Producers** make their own food; **consumers** eat other organisms (primary, secondary…); **decomposers** (fungi and bacteria, microorganisms) break down dead matter and wastes.
- One animal can feed at more than one level.

## Exit ticket

:::keep-together

**In a food web, why does the arrow point from the gum leaves to the koala?**

{{lines-3}}

:::


:::teacher-note

**Answer:** Arrows show the direction energy flows: from the food (gum leaves) into the eater (koala).

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