The carbon cycle

In a nutshell

Carbon is an important element that makes up living things and it has to be recycled as there is only a fixed amount in the atmosphere. It is taken up by plants from the air and soil during photosynthesis and then passed onto animals who eat plants. When the animals die and decompose the carbon is returned to the air and soil.

Recycling of materials in an ecosystem

1.	Plants take in carbon (from carbon dioxide) and oxygen from the air and nitrogen from the soil.
2.	These elements are turned into complex compounds such as carbohydrates, proteins and fats that make up living organisms. They can then be passed along food chains when animals eat plants and other animals.
3.	These elements are recycled. Waste products and dead organisms are broken down by decomposers so the elements will be returned to the soil or air. Plants will then take up these elements again.

The carbon cycle

There is only a certain amount of carbon in the atmosphere so it has to be recycled.

Biology; Ecosystems and material cycles; KS4 Year 10; The carbon cycle

1.	Carbon dioxide in the atmosphere.
2.	Green plants use carbon from carbon dioxide to make carbohydrates, fats and proteins.
3.	The fossilisation of plants and animals.
4.	Carbon dioxide is stored in fossil fuels (coal/oil).
5.	When plants and animals die, they decompose and turn into useful products.
6.	Decomposition is done by microorganisms that respire and release carbon dioxide into the air.
7.	Carbon is passed to animals when they eat plants.
8.	When plants and animals respire they release carbon dioxide back into the air.
9.	The burning of plant and animal products such as wood or fossil fuels released carbon dioxide back into the air.

Note: Decomposition allows habitats to be maintained for the organisms that live there as nutrients are returned to the soil and waste material doesn't pile up.