Explain how an increase in temperature and an increase in oxygen availability affect the rate of decomposition in a woodland ecosystem.

Pearson Edexcel International GCSE Biology (4BI1) — 4.1 The organism in the environment · Explain · 4 marks · View as Markdown

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

Decomposers break down dead plant and animal material on the forest floor. The rate at which this decomposition occurs is influenced by several abiotic factors.

Model answer (4 marks)

Higher temperature increases the rate of decomposition because it raises the activity and metabolic rate of decomposers – enzymes work faster and microorganisms are more active.

Increased oxygen availability also increases the rate of decomposition because decomposers respire aerobically, using oxygen to release more energy and break down dead material more efficiently.

Examiner tips

Use the exact phrases "higher temperature increases the rate of decomposition" and "increased oxygen availability increases the rate of decomposition". Include the reasons: "enzymes work faster" and "decomposers respire aerobically". Keep each point short and to the point to fit the 4‑mark structure.

Common mistakes

Mixing up the effect of temperature and oxygen – writing that temperature reduces decomposition. Using vague terms like "more activity" without linking to enzymes or respiration. Leaving out the word "oxygen" or the phrase "aerobically".

Mark scheme (4 marks)

Higher temperature increases the rate of decomposition
Because higher temperature increases the activity / metabolic rate of decomposers (enzymes work faster / microorganisms are more active)
Increased oxygen availability increases the rate of decomposition
Because decomposers respire aerobically using oxygen, releasing more energy to break down dead material / decomposers are more active when oxygen is available

Key terms in this question

decomposition