All lessons › Food chains and decomposers › Lesson 3
Australian primary science · Year 4 · Lesson 3 of 3
Clean-up crew
Inquiry question: What happens to leaves after they fall, and who helps?
Check practical materials
Observing
What students learn
Decomposers, such as fungi and earthworms, and small animals like slaters, break dead leaves into smaller and smaller pieces until they become part of the soil. This returns nutrients for producers to use.
Success criteria
- I can find signs of decomposition in leaf litter.
- I can describe and draw what I observe.
- I can explain how decomposers help producers.
Preparation and materials
Before this lesson: Students can build food chains and know decomposers break down dead things (lesson 2).
- Leaf litter with the top layer of soil, collected by the teacher just before the lesson — 1 bucket (about 2 cups per pair)
- White paper plates, or sheets of white paper — 13
- Plastic spoons or paddle-pop sticks (no bare hands) — 26 (one per student)
- Clear plastic cups to look closely at small animals — 13
- Magnifying glasses, if the school has them (optional) — 13
- Gardening gloves for the teacher (and disposable gloves for students, if available) — 1 pair
- Tray or old newspaper to check the litter on — 1
- Soap and paper towel for hand washing — 1 set
Teacher setup
- Wearing gloves, scoop leaf litter and the top few centimetres of soil from under a tree or garden bed. Choose a spot without animal droppings, broken glass or rubbish. Don’t use bagged potting mix or compost (it can carry harmful germs).
- Tip it onto a tray and check for spiders, ants, centipedes and scorpions before sharing it out; leave them outside.
- Put about two cups of litter on each pair’s plate.
Safety and adaptations
- The teacher collects the litter with gloves; students do not dig.
- Use spoons or sticks (and gloves if you have them), not bare hands, and never touch spiders, centipedes or any animal that might sting or bite.
- Don’t touch or taste mushrooms or any fungi.
- Students with asthma or a mould allergy observe without handling the litter, and sit back from it. Cover any cuts on hands.
- Wash hands with soap afterwards.
- Handle small animals gently and return them where they were found.
Review your school policies and curriculum requirements before teaching.
How to investigate
The lesson sequence should leave pupils with evidence to interpret, not only an activity to finish.
- Pairs spread the litter on their plate with spoons.
- Sort the leaves from whole, to holey, to crumbly, to soil-like.
- Look for decomposers and small animals: earthworms, slaters, millipedes, beetles, white fungus threads.
- Gently scoop a small animal into a clear cup with a spoon to look closely, then return it.
- Record what you found and its role.
Teacher modelling prompt
Hold up two leaves: one whole and one full of holes and crumbly. Think aloud: “This leaf has holes and soft brown patches. Something has been breaking it down. I’ll look for who did it: tiny animals, or white threads of fungi.” Draw the leaf and label what you see.
Record and explain evidence
Recording question: What happens to leaves after they fall, and who helps?
| What we found | What it looked like | Living or once-living? | Its role (producer, consumer, decomposer, or being broken down) |
|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
What did we observe that supports either claim?
Check understanding
What should pupils know? What is the job of a decomposer?
Explain with evidence: Why might fewer earthworms and fungi in a garden mean the plants grow less well?
Apply the idea: A family adds their fruit and vegetable scraps to a compost bin. Explain what happens to the scraps and why it helps their garden.
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.