The complete carbon cycle looks. Carbon exists in many forms in the global carbon cycle including carbon dioxide CO 2 and methane CH 4 two prominent greenhouse gasesCO 2 exists naturally but is also increasingly being emitted into the atmosphere through human activities like the burning of fossil fuels. I Need An Explanation Of Oxygen Cycle With A Diagram Meritnation Com Oxygen Cycle For Kids Nitrogen Cycle At least 12 of the oxygen we breathe comes from the photosynthesis of marine plants. . Nitrogen Cycle Gaseous Cycle Apart from carbon hydrogen and oxygen nitrogen is the most prevalent element in living organisms. All aerobic organisms use free oxygen for respiration. Carbon cycle in biology circulation of carbon in various forms through nature. The carbon cycle is the process through which carbon elements are interchanged between the biosphere geosphere hydrosphere and atmosphere in the Earth. Cardiac Measurements and