Explain how carbon in the bodies of dead organisms is returned to the atmosphere.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Decomposers such as bacteria and fungi break down the dead organisms.
They carry out cellular respiration.
Respiration releases carbon dioxide.
The carbon in the organic molecules of the dead organism is converted to CO₂.
CO₂ is released into the atmosphere where it can be used by plants for photosynthesis.
They carry out cellular respiration.
Respiration releases carbon dioxide.
The carbon in the organic molecules of the dead organism is converted to CO₂.
CO₂ is released into the atmosphere where it can be used by plants for photosynthesis.
Examiner tips
- Use the exact terminology: decomposers, respiration, CO₂, photosynthesis.
- Show the sequence of steps clearly and link each to the next.
- Include the word ‘atmosphere’ to demonstrate the cycle.
- Keep the answer concise – one sentence per point for 5 marks.
Common mistakes
- Omitting the role of decomposers or respiration.
- Using ‘breathing’ instead of ‘respiration’. Failing to mention the atmosphere or photosynthesis.
Mark scheme (5 marks)
- Decomposers (bacteria / fungi) break down the dead organisms
- Decomposers carry out respiration
- Respiration releases carbon dioxide
- The carbon in the organic molecules of the dead organism is converted to carbon dioxide
- Carbon dioxide returns to the atmosphere where it can be used by plants for photosynthesis
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →