The arrows indicate the movement of the element among the earth's spheres. Green plants play a very important role in the carbon cycle. This process is called photosynthesis . There are two main steps in photosynthesis. First, plants trap the sun's light energy in a compound called chlorophyll.
Animals eat plants to obtain the energy trapped during photosynthesis.
As the animals' bodies break down the carbohydrates in the plant tissue, CO 2 is released to the atmosphere. This process is called respiration . Plants, too, respire as they break down the organic molecules in themselves in order to release the stored energy. Plants and animals also release CO 2 to the atmosphere when they decompose or decay. The chemical reaction for this process is the same as that for respiration.