Exam Focus

Exam Focus

The carbon cycle appears regularly on AQA Paper 2, often paired with climate change. Questions frequently ask students to trace carbon through the cycle or explain human impacts. Key patterns include:

• Process questions (2-3 marks): "Name the processes by which carbon is returned to the atmosphere" — list respiration, combustion, decomposition (and fossil fuel burning).
• Diagram questions (3-4 marks): Add missing arrows or labels to a carbon cycle diagram; state which process each arrow represents.
• Human impact questions (4-6 marks): Explain how deforestation or burning fossil fuels increases atmospheric CO2 — always link to specific carbon cycle processes (reduced photosynthesis AND increased combustion for deforestation).
• Carbon sink/source questions (2-3 marks): Distinguish between carbon sinks and sources; explain why an activity converts a sink to a source.

Common mark-losing errors: Saying plants only photosynthesise (they also respire); saying decomposition doesn't produce CO2; forgetting that deforestation reduces photosynthesis as well as increasing combustion; describing peat bogs as releasing CO2 without linking to decomposers gaining access to oxygen.

Edexcel 1BI0 Paper 2 (T9 — Ecosystems and Material Cycles): Edexcel carbon cycle questions often include atmospheric CO₂ concentration data — graphs showing CO₂ levels over decades or centuries, with questions asking you to describe the trend and explain it in terms of human activities (fossil fuel combustion, deforestation). "Evaluate" questions may present data on carbon capture or rewilding schemes, asking you to assess their effectiveness. Edexcel may also ask you to compare natural carbon fixation (photosynthesis) with industrial processes, or to explain why fossil fuel burning has a greater net effect on atmospheric CO₂ than decomposition does. Edexcel mark schemes use "Accept…" and "Allow…" for equivalent process descriptions.