Explain why decomposition is important for the recycling of materials in an ecosystem.

OCR GCSE Biology A: Gateway Science (J247) — B4.1 Ecosystems · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

In a woodland ecosystem, fallen leaves and dead animals accumulate on the forest floor. Decomposers, including bacteria and fungi, break down this dead material over time.

Model answer (4 marks)

Decomposers break down dead and decaying matter into simpler substances.
Mineral ions are returned to the soil.
Carbon dioxide is released into the atmosphere via decomposer respiration.
This allows producers to absorb mineral ions and CO₂, enabling growth and supporting the rest of the community.

Examiner tips

Use the exact terms ‘decomposers’, ‘mineral ions’, ‘carbon dioxide’, ‘producers’. Show the causal chain: decomposition → mineral ions & CO₂ → plant uptake → ecosystem support. Keep each point brief but complete to hit the 4 marks.

Common mistakes

Confusing decomposers with predators. Failing to mention CO₂ release. Using vague terms like ‘nutrients’ instead of ‘mineral ions’.

Mark scheme (4 marks)

Decomposers break down dead and decaying matter into simpler substances
Mineral ions are returned to the soil
Carbon dioxide is released into the atmosphere (via respiration by decomposers)
This allows producers/plants to absorb mineral ions and carbon dioxide so they can grow, supporting the rest of the community

Key terms in this question

decomposition · ecosystem