CIE iGCSE Co-Ordinated Science B18.3 Carbon cycle Exam Style Questions Paper 1
▶️ Answer/Explanation
Transpiration is the evaporation and movement of water through plants and out via the stomata — it is part of the water cycle, not the carbon cycle.
Combustion, fossilisation, and photosynthesis all involve the movement of carbon between the atmosphere, living organisms, and the Earth, so they are all parts of the carbon cycle.
✅ Answer: (C)
Combustion, fossilisation, and photosynthesis all involve the movement of carbon between the atmosphere, living organisms, and the Earth, so they are all parts of the carbon cycle.
✅ Answer: (C)
▶️ Answer/Explanation
In the carbon cycle diagram, process X shows an arrow from atmospheric \(\text{CO}_2\) into plants/organic compounds; this is photosynthesis — the only process that removes \(\text{CO}_2\) from the atmosphere and fixes it into organic molecules.
Respiration, combustion, and decomposition all release \(\text{CO}_2\) back into the atmosphere (arrows pointing in the opposite direction), so X must be photosynthesis.
✅ Answer: (C)
Respiration, combustion, and decomposition all release \(\text{CO}_2\) back into the atmosphere (arrows pointing in the opposite direction), so X must be photosynthesis.
✅ Answer: (C)
▶️ Answer/Explanation
Photosynthesis removes carbon dioxide from the air, while respiration and combustion both release carbon dioxide into the air.
Decomposition releases carbon dioxide as decomposers respire while breaking down dead matter.
Only one row correctly states both the process named and whether it adds or removes atmospheric carbon dioxide.
✅ Answer: (B)
Decomposition releases carbon dioxide as decomposers respire while breaking down dead matter.
Only one row correctly states both the process named and whether it adds or removes atmospheric carbon dioxide.
✅ Answer: (B)
▶️ Answer/Explanation
In darkness, plants cannot photosynthesise, so both plants and animals only respire.
Respiration takes in oxygen and releases carbon dioxide, so the carbon cycle gas involved is carbon dioxide, not oxygen.
Identifying the arrows that represent carbon dioxide being released by both groups of organisms gives the gases that are part of the carbon cycle.
✅ Answer: (B)
Respiration takes in oxygen and releases carbon dioxide, so the carbon cycle gas involved is carbon dioxide, not oxygen.
Identifying the arrows that represent carbon dioxide being released by both groups of organisms gives the gases that are part of the carbon cycle.
✅ Answer: (B)
▶️ Answer/Explanation
Photosynthesis uses carbon dioxide and water in the presence of light to produce glucose and oxygen, thereby removing \(\text{CO}_2\) from the atmosphere: \(6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2\).
Combustion, decomposition, and respiration all release \(\text{CO}_2\) back into the atmosphere, so they are the opposite process.
✅ Answer: (C)
Combustion, decomposition, and respiration all release \(\text{CO}_2\) back into the atmosphere, so they are the opposite process.
✅ Answer: (C)