biogeochemical cycle

Science Dictionary
biogeochemical cycle  [%PREMIUM_LINK%]     (bī'ō-jē'ō-kěm'ĭ-kəl)  Pronunciation Key 
The flow of chemical elements and compounds between living organisms and the physical environment. Chemicals absorbed or ingested by organisms are passed through the food chain and returned to the soil, air, and water by such mechanisms as respiration, excretion, and decomposition. As an element moves through this cycle, it often forms compounds with other elements as a result of metabolic processes in living tissues and of natural reactions in the atmosphere, hydrosphere, or lithosphere. See more at carbon cycle, nitrogen cycle.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

biogeochemical cycle

any of the natural circulation pathways of the essential elements of living matter. These elements in various forms flow from the nonliving (abiotic) to the living (biotic) components of the biosphere and back to the nonliving again. In order for the living components of a major ecosystem (e.g., a lake or forest) to survive, all the chemical elements that make up living cells must be recycled continuously

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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