Cycles in ecosystems
Edexcel GCSE Biology revision on Cycles in ecosystems. Aligned to the Pearson Edexcel GCSE Biology 1BI0 specification. This bank has 25 practice questions on this topic.
Sample questions (3 of 25)
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Question 1
In the carbon cycle, CO2 is removed from the atmosphere by...
- A) Combustion
- B) Photosynthesis by plants + algae
- C) Respiration
- D) Decomposition
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Answer: Photosynthesis by plants + algae
Carbon cycle: CO2 absorbed from air by plants -> photosynthesis -> glucose -> plant body. Eaten by herbivores -> respiration releases CO2 back. Death -> decomposers respire -> CO2 back. Combustion of fossil fuels also releases CO2. Net effect of humans: more CO2 going in than coming out -> atmospheric CO2 rising.
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Question 2
In the water cycle, water vapour returns to land mainly as...
- A) Wind
- B) Precipitation
- C) Lightning
- D) Pollen
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Answer: Precipitation
Water cycle: EVAPORATION from oceans + transpiration from plants -> water vapour rises -> CONDENSES in clouds -> PRECIPITATION (rain, snow, hail) -> falls to ground -> RUN-OFF (rivers, streams) or INFILTRATION into soil + groundwater -> back to ocean. Powered by the Sun (drives evaporation) + gravity (pulls water down).
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Question 3
Decomposers (e.g. bacteria, fungi) recycle nutrients by...
- A) Eating live animals
- B) Breaking down dead organisms + faeces, releasing minerals back into soil
- C) Photosynthesising
- D) Filtering air
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Answer: Breaking down dead organisms + faeces, releasing minerals back into soil
Bacteria + fungi break down dead matter -> releases nutrients (N, P, K, etc.) into soil -> plants absorb them. Without decomposers, all the dead stuff would accumulate + nutrients would stay locked up. Carbon, nitrogen, phosphorus, and water cycles all depend on decomposers. Speed of decomposition depends on: temperature (warm = fast), moisture, oxygen (aerobic decomposers need O2).
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22 more questions on Cycles in ecosystems — plus mistakes tracking and spaced repetition across the whole Biology spec.