How to Revise Ecosystems — Pearson A-Level Biology
Describe the carbon and nitrogen cycles. Explain the role of microorganisms in nutrient cycling
Examiner Tips for Ecosystems
- Draw and label diagrams of both cycles.
- Use mnemonics to remember the order of processes.
- Understand the difference between aerobic and anaerobic decomposition.
- Use diagrams to support explanations of energy flow.
- Remember the 10% rule for energy transfer.
- Link energy flow to the concept of biomass.
- Use diagrams to show stages.
- Mention examples like sand dunes or abandoned farmland.
Common Mistakes in Ecosystems
- Confusing nitrogen fixation with nitrification.
- Forgetting that respiration and photosynthesis are key to carbon cycle.
- Not mentioning the role of bacteria in the nitrogen cycle.
- Confusing energy flow with nutrient cycling.
- Assuming energy is recycled within an ecosystem.
- Misidentifying producers and consumers in a food chain.
Key Marking Points
- Describe the stages of the carbon cycle.
- Describe the stages of the nitrogen cycle.
- Explain the role of microorganisms in decomposition and nitrogen fixation.
- Identify human impacts on nutrient cycles.
- Define trophic levels and give examples.
- Explain why energy transfer between trophic levels is inefficient.