Explain why decomposers are essential for returning nutrients to the soil, and describe what would happen to plant growth if decomposers were absent from an ecosystem.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Decomposers break down dead organisms and waste, releasing minerals such as nitrates and phosphates back into the soil.
Without decomposers, dead organic matter would accumulate and nutrients would not be recycled.
Plants would then lack sufficient minerals and nitrates, leading to reduced or stunted growth.
Without decomposers, dead organic matter would accumulate and nutrients would not be recycled.
Plants would then lack sufficient minerals and nitrates, leading to reduced or stunted growth.
Examiner tips
- Use the term ‘decomposers’ and mention ‘nitrates’/‘phosphates’ to hit key points. Show the cause–effect chain: decomposition → nutrient release → plant uptake → growth. Keep the answer concise, 4 points total.
- common_mistakes
- :
- Confusing decomposers with predators. Failing to mention specific nutrients (e.g., nitrates). Over‑extending the answer with irrelevant details.
Mark scheme (4 marks)
- Decomposers break down / digest dead organisms (and waste materials)
- This releases minerals / nutrients (e.g. nitrates / phosphates) back into the soil
- Without decomposers, dead organic matter / minerals would not be recycled / returned to the soil
- Plants would not be able to absorb sufficient minerals / nitrates, so growth would be reduced / stunted
Key terms in this question
Related
- All WJEC GCSE Biology (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →