# Explain how water content and oxygen availability affect the rate of decomposition of dead plant material in a compost heap.

> Edexcel GCSE Biology (1BI0) — 9.3 Material cycles · Explain · 4 marks

> A gardener adds dead plant material to a compost heap. Over several weeks, the material breaks down into compost that can be used as a fertiliser.

## Mark scheme (4 marks)

1. Higher water content increases the rate of decomposition
2. Because decomposers / microorganisms need water to survive / carry out enzyme-catalysed reactions
3. Higher oxygen availability increases the rate of decomposition
4. Because decomposers / microorganisms use oxygen for aerobic respiration to release energy to break down dead material

## Key terms

- [decomposition](https://www.gradenine.co.uk/glossary/decomposition)
- [water content](https://www.gradenine.co.uk/glossary/water-content)
- [oxygen availability](https://www.gradenine.co.uk/glossary/oxygen-availability)

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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/explain-how-water-content-and-oxygen-e16da55f) · Published by Druglandscape Ltd.