Explain why micro-organisms such as bacteria and fungi are described as decomposers, and explain why this role is important in ecosystems.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Micro‑organisms such as bacteria and fungi are called decomposers because they break down dead organic material, including dead organisms and waste.
They release nutrients and minerals into the soil.
Plants can absorb these nutrients from the soil.
Thus decomposers recycle nutrients, allowing them to be reused in food chains and ecosystems.
They release nutrients and minerals into the soil.
Plants can absorb these nutrients from the soil.
Thus decomposers recycle nutrients, allowing them to be reused in food chains and ecosystems.
Examiner tips
- Use the term ‘decomposers’ first. Show the sequence: break down → release nutrients → plant uptake → recycling. Keep each point short and use exam‑style wording.
Common mistakes
- Confusing decomposers with producers. Omitting the step that nutrients are taken up by plants. Using vague words like ‘help’ instead of ‘recycle’.
Mark scheme (4 marks)
- Decomposers break down dead organic material / dead organisms / waste material
- They release nutrients / minerals into the soil
- These nutrients can then be absorbed / taken up by plants
- This recycles nutrients / allows nutrients to be reused in food chains / ecosystems
Key terms in this question
decomposers · ecosystems · micro-organisms
Related
- All WJEC GCSE Biology (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →