Carbon is an essential element for life on Earth and most biological molecules include carbon atoms. Carbon is present in:
Stage one of the carbon cycle
The carbon cycle is easiest to understand in terms of its processes and the conversion of carbon that they undertake. The three key processes and their conversions are shown in the table below.
|Process||Carbon starts as||Carbon ends as|
|Combustion (burning)||Fuel (eg methane or wood)||Carbon dioxide|
Almost all living things depend on photosynthesis in producers (eg green plants). This process converts carbon dioxide into carbohydrates which support other living things. Animals feed on plants, so the carbon compounds are passed along food chains. Animals and plants respire, releasing carbon dioxide back into the atmosphere.
When dead plants and animals are decomposed by microorganisms, carbon dioxide is released to the atmosphere and mineral ions are returned to the soil.