# A student leaves a piece of bread in a warm, damp environment. After two weeks, the bread is covered in mould and has significantly decreased in mass. Explain why the conditions in the student's environment led to the bread decaying rapidly, and describe what happens to the materials in the bread during decomposition.

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

> Decomposers such as bacteria and fungi break down dead organic material. The rate of decomposition is affected by temperature, moisture and oxygen availability. During decomposition, complex organic molecules are broken down and nutrients are released back into the environment.

## Mark scheme (5 marks)

1. Warm temperatures increase the rate of enzyme activity in decomposers
2. Damp/moist conditions are needed for decomposers to survive and function
3. Decomposers (fungi/bacteria) secrete enzymes onto the bread to break down complex organic molecules
4. The organic molecules in the bread are broken down into simpler/smaller molecules (e.g. carbon dioxide, water, mineral ions/nutrients)
5. These nutrients/minerals are released back into the environment/soil, recycling them for use by other organisms (e.g. plants)

## Key terms

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

## 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/a-student-leaves-a-piece-of-76047a19) · Published by Druglandscape Ltd.