Decomposers: Nature's Recyclers — Answers
Answer sheet with model answers and success criteria for the Year 4 ecosystems & food chains worksheet.
Success TutoringWorksheetsAnswer sheetYear 4 · Science · Ecosystems & Food ChainsDecomposers: Nature's Recyclers — Answers
Part A: The clean-up crew
Read the passage. Then circle the best answer.
When plants and animals die, they do not stay around for ever. They are broken down by decomposers. Breaking down is called decay or decomposition.
The main decomposers are fungi (such as mushrooms and mould) and bacteria (living things too small to see). Animals such as earthworms, beetles and millipedes help by eating dead material and breaking it into smaller pieces.
As decomposers feed, they release nutrients from the dead material back into the soil. Plants take in these nutrients through their roots and use them to grow. Then animals eat the plants. This is how nutrients are recycled in an ecosystem.
Decomposers work fastest when it is warm and damp and there is some air. Cold, dry conditions slow decay down — that is one reason we keep food in the fridge.
- Amake food from sunlight
- Bbreak down dead plants and animals
- Chunt live animals
- Dmake rain
Answer: break down dead plants and animals
Decomposers feed on dead and decaying material and break it down.
- Aa mushroom
- Ba hawk
- Ca rabbit
- Da sunflower
Answer: a mushroom
Mushrooms are fungi. Fungi break down dead material.
- AThey eat the plants' leaves.
- BThey return nutrients to the soil.
- CThey block the sunlight.
- DThey make the soil dry.
Answer: They return nutrients to the soil.
When decomposers break down dead material, nutrients go back into the soil for plants to use.
- Acold and dry
- Bwarm and damp
- Cfrozen
- Dsealed in a dry jar
Answer: warm and damp
Decomposers grow best when it is warm and damp, with some air.
- ADead things would pile up and soil would run out of nutrients.
- BPlants would grow faster.
- CThere would be more rain.
- DNothing would change.
Answer: Dead things would pile up and soil would run out of nutrients.
Without decomposers, dead material would not break down and nutrients would not be recycled.
Part B: Recycling nutrients
- decomposer
- nutrients
- decay
- substances plants need to grow
- the breaking down of dead things
- a living thing that breaks down dead material
Answer: decomposer → a living thing that breaks down dead material; nutrients → substances plants need to grow; decay → the breaking down of dead things
Answer: fungi
Answer: damp
Also accept: moist or wet.
Answer: Decomposers break the leaf down, releasing its nutrients into the soil. The new plant takes in the nutrients through its roots.
Part C: True or false?
Write True or False.
Answer: True
Bacteria are microscopic living things.
Answer: False
Decomposers are essential: they recycle nutrients and clear away dead material.
Answer: True
Cold slows down the decomposers.
Answer: True
This helps fungi and bacteria break the material down faster.
Part D: Working scientifically: mouldy bread
Do not open bags of mouldy food. Look through the bag, then throw it away sealed.
Hana sealed three slices of the same bread in clear bags for one week. A: dry, warm cupboard — a few small spots of mould. B: damp, warm cupboard — covered in mould. C: damp, in the fridge — almost no mould.
Answer: Slice B — the warm, damp one.
Answer: Whether the bread was damp or dry, and whether it was kept warm or cold.
Model answer: Mould grows fastest on bread that is warm and damp. Mould is a decomposer (a fungus), and decomposers grow best in warm, damp conditions. Cold and dry conditions slow them down.
Success criteria:
- Links warm and damp to the most mould
- Identifies mould as a decomposer
- Explains cold or dry slows decay
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
- Celebrate what went well first, then pick one thing to work on next.