According to Locust Valley Central School District, the carbon dioxide-oxygen cycle is the process through which carbon dioxide and oxygen move through the natural environment by photosynthesis, respiration, combustion and decomposition. Plants and animals are important to the carbon dioxide-oxygen cycle.
During photosynthesis, plants absorb carbon dioxide through openings in their leaves. In the chlorophyll or green pigment in the leaves, the carbon dioxide, along with water and sunlight, is converted to sugar, used for energy in the plant, and oxygen and water vapor, which are released into the air. During respiration, animals breathe in the oxygen in the atmosphere and use it along with food to create energy. This process releases carbon dioxide which animals release into the air. Combustion is any source of burning, such as fires, volcanoes and using fossil fuels for energy, which also releases carbon dioxide into the air. Decomposition is when dead plants and animals breakdown. This returns the carbon dioxide and oxygen from the plant or the animal's body back to the environment.