Which process removes CO₂ from the air?
Reveal answer
Photosynthesis.
Key words: photosynthesis
5(c) CYCLES WITHIN ECOSYSTEMS · RECALL
5.10 The carbon cycle
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Processes returning CO₂ to the air?
Reveal answer
Respiration + combustion + decomposition.
Key words: combustion
How do fossil fuels form?
Reveal answer
Dead organisms not decayed → compressed over millions of years.
Key words: millions
What is meant by the term carbon cycle?
Reveal answer
The continuous movement of carbon between the atmosphere, organisms, oceans and rocks.
Key words: carbon cycle
What is meant by the term combustion?
Reveal answer
Burning a fuel in oxygen, releasing carbon dioxide and energy.
Key words: combustion
What is meant by the term fossil fuel?
Reveal answer
A fuel formed over millions of years from the remains of organisms.
Key words: fossil fuel
What is meant by the term decomposition?
Reveal answer
The breakdown of dead organic matter by decomposers.
Key words: decomposition
Processes in the carbon cycle, Photosynthesis. Effect on atmospheric CO₂? Organisms or source involved?
Reveal answer
Effect on atmospheric CO₂: Removes CO₂. Organisms or source involved: Plants, algae, some bacteria.
Key words: Photosynthesis
Processes in the carbon cycle, Respiration. Effect on atmospheric CO₂? Organisms or source involved?
Reveal answer
Effect on atmospheric CO₂: Releases CO₂. Organisms or source involved: All living organisms.
Key words: Respiration
Processes in the carbon cycle, Decomposition. Effect on atmospheric CO₂? Organisms or source involved?
Reveal answer
Effect on atmospheric CO₂: Releases CO₂ (by decomposer respiration). Organisms or source involved: Bacteria and fungi.
Key words: Decomposition
Processes in the carbon cycle, Combustion. Effect on atmospheric CO₂? Organisms or source involved?
Reveal answer
Effect on atmospheric CO₂: Releases CO₂ rapidly. Organisms or source involved: Burning fossil fuels and biomass.
Key words: Combustion
Processes in the carbon cycle, Fossilisation. Effect on atmospheric CO₂? Organisms or source involved?
Reveal answer
Effect on atmospheric CO₂: Locks carbon away for millions of years. Organisms or source involved: Incompletely decomposed remains.
Key words: Fossilisation
True or false, and why? “Plants only photosynthesise and do not respire.”
Reveal answer
False. Plants respire continuously; in bright light photosynthesis is usually faster than respiration.
True or false, and why? “Decomposers release CO₂ by breaking molecules apart.”
Reveal answer
False. They digest the material and release CO₂ through their own respiration.
True or false, and why? “Combustion and respiration are the same process.”
Reveal answer
False. Both release CO₂, but combustion is burning; respiration is enzyme-controlled reactions in cells.