The simplest description of the carbon cycle involves two primary processes.

• Photosynthesis- During photosynthesis, plants absorb carbon dioxide from the atmosphere and release oxygen into the air.
• Respiration- When animals breathe, they take in oxygen and then release carbon dioxide into the atmosphere.

This constant exchange of gases shows one way in which plants and animals interact in an ecosystem.

Sometimes organic^* matter accumulates and forms coal and oil. In this case, it may take a long time before the carbon is released back into the environment.

As a whole, the earth's atmosphere contains approximately 0.03% carbon dioxide. This number is on the rise. Human activities such as desforestation and burning fossil fuels are two reasons why this number is rising.