This exam tips covers Exam Tips for Decomposition within Decomposition for GCSE Biology. Topic 4: Decomposition It is section 11 of 12 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
💡 Exam Tips for Decomposition
🎯 Common Question Types:
- Explain how [factor] affects the rate of decomposition (2–3 marks)
- Describe/evaluate the Required Practical on decay (3–4 marks)
- Compare decomposition rates in different environments (2–3 marks)
- Explain why biogas generators must be kept anaerobic (2 marks)
📝 Key Command Words:
- Explain: Give a reason — always link factor to enzyme activity to decomposition rate
- Describe: State what happens — no reason needed, but include all key steps
- Evaluate: Judge a suggestion — state whether it is correct or incorrect and why
- Suggest: Apply knowledge to a new context — use TOMP factors
⚠️ Common Mistakes to Avoid:
- Saying bacteria "eat" or "swallow" dead material — they secrete enzymes externally
- Forgetting fungi are also major decomposers, not just bacteria
- Saying "higher temperature = faster decomposition" without mentioning denaturation above the optimum
- Confusing decomposers (bacteria/fungi) with detritivores (earthworms/woodlice)
- Forgetting that biogas requires anaerobic conditions — oxygen destroys methane production
Practice questions for Decomposition
Which organisms are the main decomposers?
Explain how temperature affects the rate of decomposition.
Quick recall flashcards
What is decomposition and who carries it out?
Decomposition is the breakdown of dead organisms and waste into simpler substances.
Carried out by decomposers: mainly bacteria and fungi.
This releases nutrients back into the soil for plants to use.
How do decomposers feed? (saprotrophic nutrition)
Decomposers use saprotrophic nutrition:
1. Secrete enzymes onto dead material (extracellular digestion)
2. Enzymes break down large molecules
3. Decomposer absorbs the small soluble products