see also : [[plants and photosynthesis]]
- Photosynthesising plants remove CO2 from the atmosphere.
- Eating passes carbon compounds along a food chain.
- Respiration in plants and animals returns CO2 to the atmosphere.
- Organisms die and decompose. Decomposers (bacteria and fungi) break down dead. material and release CO2 via respiration.
- Combustion of materials (e.g. wood, fossil fuels) releases CO2