# A fallen oak tree in a forest is gradually broken down over several years. Explain the conditions that would cause the tree to decompose most rapidly.

> Pearson Edexcel A-Level Biology A (9BI0) — 5.5 Decomposition and decay · Explain · 5 marks

> Decomposers such as bacteria and fungi are responsible for breaking down dead organic material, including fallen trees, in forest ecosystems. The rate at which this decomposition occurs depends on several environmental conditions.

## Mark scheme (5 marks)

1. High temperature increases the rate of decomposition
2. Because enzymes in decomposers work faster / have more kinetic energy at higher temperatures (up to the optimum)
3. Moist / high moisture conditions increase the rate of decomposition
4. Presence of oxygen / aerobic conditions increase the rate of decomposition
5. Because decomposers need to respire to release energy for growth and reproduction / metabolic processes

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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