This exam focus covers Exam Focus within Decomposition for GCSE Biology. Topic 4: Decomposition It is section 10 of 12 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 10 of 12
Practice
15 questions
Recall
20 flashcards
Exam Focus
Frequently ExaminedDecomposition is examined regularly on AQA Paper 2, often in the context of the Required Practical (RPA6/RPA10 — investigating factors affecting decomposition rate). Questions frequently link decomposition to the carbon cycle and nutrient recycling. Key patterns include:
- Factor explanation questions (2-3 marks): "Explain how temperature affects the rate of decomposition" — always link to enzyme activity, state the optimum, and explain denaturation at high temperatures.
- Required Practical questions (3-4 marks): "Describe how you would investigate the effect of moisture on the rate of decomposition of leaf litter" — state the independent variable, dependent variable, control variables, and how you would measure the rate.
- Comparison questions (2-3 marks): "Explain why decomposition is slower in peat bogs than in garden soil" — link to anaerobic conditions, low pH, and reduced enzyme activity.
- Biogas questions (2-3 marks): State conditions needed for biogas production and explain why these conditions are necessary.
Common mark-losing errors: Saying "bacteria eat dead material" rather than secreting enzymes externally; saying high temperature always speeds decomposition (ignoring denaturation); forgetting fungi as major decomposers; confusing decomposers with detritivores.