The Nitrogen, Phosphorous, and Carbon Cycles
The nitrogen cycle follows the movement of nitrogen in its different forms. Nitrogen gas makes up almost 80% of the atmosphere and most nitrogen enters into the ecosystem via nitrogen-fixing bacteria, but many organisms still struggle with nitrogen availability because they cannot use it in that form. The process of making nitrogen accessible is called nitrogen fixation. Many forms of bacteria are capable of this. Many of these bacteria are found in the soil, but some species have a symbiotic relationship with microbes which are capable of fixation. Other key processes include nitrification, denitrification, and ammonification.
The phosphorous cycle follows the movement of phosphorous through the biosphere. Phosphorous is found in many forms, both organic and inorganic, but is most commonly found in the phosphate ion. Phosphorous is essential for both plants and animals. In biotic processes, plants remove phosphorous from the soil, animals eat plants and so on. In abiotic (nonliving) processes, phosphate is released by rocks due to weathering, then is deposited in the soil or water through runoff or leaching.
The carbon cycle is a cycle where carbon is exchanged throughout the Earth's atmosphere, the biosphere, the oceans, and sediments. Carbon in living organisms turns to soil when they die, entering the sediment. Then it might return to the biosphere in the form of a plant growing out of that soil which is eaten by an animal. That animal emits carbon in the form of carbon dioxide as a product of respiration.
Last modified: Wednesday, 7 March 2012, 9:13 AM