The Carbon Cycle
Respiration takes carbohydrates and oxygen, combines them to produce carbon dioxide, water, and energy. Photosynthesis takes carbon dioxide and water, produces carbohydrates and oxygen. The outputs of respiration are the inputs of photosynthesis, and the outputs of photosynthesis are the inputs of respiration. The reactions are also complementary in the way they deal with energy. Photosynthesis takes energy from the sun and stores it as carbohydrates; respiration releases that energy. Both plants and animals carry on respiration, but only plants can carry on photosynthesis.
The chief reservoirs for carbon dioxide are the oceans and the rocks. Carbon dioxide dissolves readily in water. Once there, it may precipitate as a solid rock known as calcium carbonate. Corals and algae encourage this reaction and build up limestone reefs in the process. On land and in the water, plants take up carbon dioxide and convert it into carbohydrates through photosynthesis. This carbon in the plants now has three possible fates. It can be liberated to the atmosphere by the plant through respirations; it can be eaten by an animal, or it can be present in the plant when the plant dies.
When an animal or a plant dies, two things can happen to the carbon in it. It can either be released by decomposers to the atmosphere, or it can be buried intact and ultimately form coal, oil, or natural gas. The fossil fuels can be mined and when burned releases carbon dioxide to the atmosphere. Otherwise, the carbon in limestone or other, sediments can only be released to the atmosphere when volcanoe erupts, or when they are pushed to the surface and slowly weathered away.
Humans have a great impact on the carbon cycle because when we burn fossil fuels we release excess carbon dioxide into the atmosphere. This means that more carbon dioxide goes into the oceans, and more is present in the atmosphere. This rise in the atmosphere causes global warning.