Write importance of phosphorus cycle in ecosystems.

Phosphorus is an essential element for all living organisms which is a structural component of ATP (adenosine triphosphate), a form of cellular energy as well as DNA and RNA, which are the important life-sustaining molecules. The human body has phosphorus in the form of bones and teeth that contribute 80% of the phosphorus requirement. Phosphorus limits plant and animal growth due to its low availability in soil and water bodies. It is found in phosphate ion form (PO₄^3-) in various compounds of soil, water, and rock sediments. Unlike other biogeochemical cycles, phosphorus circulation through atmospheric changes is very poor as the major reservoir of phosphorus is in sedimentary rocks. The phosphorus of these rocks is gradually eroding, releasing phosphates to the ecosystem or leaching into the sea where it is deposited in deep sediments. 

The ratio of phosphorus to other elements in the organism is greater than the available and primary sources of phosphorus. It is an ecologically more important and limiting element that regulates productivity. Thus phosphorus cycle is known to be an important cycle of the ecosystem.