# Decomposers such as bacteria and fungi play an important role in the recycling of nutrients in ecosystems. Explain how the process of decomposition and decay returns nutrients to the soil, and describe TWO environmental conditions that slow down the rate of decomposition.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 5.5 Decomposition and decay · Explain · 5 marks

> A gardener notices that dead plant material left in a cold, waterlogged compost bin breaks down much more slowly than material in a warm, well-aerated bin.

## Mark scheme (5 marks)

1. Decomposers (bacteria and fungi) break down / digest dead organic material / organisms
2. Decomposers release nutrients / minerals into the soil (so they can be absorbed by plants)
3. Low temperature slows decomposition because decomposers / enzymes are less active
4. Waterlogged / anaerobic conditions slow decomposition because decomposers need oxygen (for aerobic respiration)
5. Linking both conditions back to slower nutrient recycling / reduced availability of minerals for plants

## Key terms

- [decomposers](https://www.gradenine.co.uk/glossary/decomposers)
- [decomposition](https://www.gradenine.co.uk/glossary/decomposition)
- [nutrients](https://www.gradenine.co.uk/glossary/nutrients)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/decomposers-such-as-bacteria-and-fungi-dee283a6) · Published by Druglandscape Ltd.