A biogeochemical cycle

A biogeochemical cycle
A biogeochemical cycle or (Nutrient cycle) is a circulating or repeatable pathway by which either a chemical element or a molecule moves through both biotic ("bio-") and abiotic ("geo-") components of an ecosystem, therefore these elements are always in circulation moving from non-living to living and then back to the non-living components of the ecosystem in a more or less circular fashion. The biogeochemical cycles concerns with the cycling of chemicals that are absorbed or ingested by organism and then passed through the food web. They ultimately end up to the air, water and soil through various metabolic activities.
Of the 90- elements known to occur in nature, some 30 or 40 are thought to be required by living organisms. The principal elements of life are carbon, hydrogen, oxygen, and nitrogen. However, a number of others are certainly important to understand as well, notably phosphorus and sulfur. Some "non-essential" elements participate in biogeochemical cycles, entering organism tissues because of chemical similarity to essential elements. For example, strontium can behave like calcium in the body.