These compounds are very important. They are present in all living things. The movement of carbon among the earth's spheres, as diagramed below, is known as the carbon cycle. 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.