Biogeochemical Cycles || carbon cycle || hydrogen cycle
Cycling of matter is a continuous process of absorption of materials for the purpose of production by the organisms and the release and the conversion of the organic matter into inorganic form.
Some important biogeochemical cycles are as follows :
Carbon cycle
The great reservoir of carbon in inorganic form and the source of almost all the carbon incorporated in the organisms is the carbon-dioxide which is found in free state in atmosphere and in dissolved state in the water of the earth.
The carbon cycle begins with the use of carbon-dioxide by green plants (producers) in the process of photosynthesis and the ultimate result is the formation of carbohydrate food. Animals eat plants and
the organic compounds are digested and resynthesized. Thus, carbon moves from producers to consumers and finally to decomposers (Bacteria, fungi and other microorganisms).
They return it to the atmosphere through decomposition of dead organic matter. Some of these organic substances (carbohydrates) are oxidized during respiration by plants and animals and direlectly carbon-dioxide into the atmosphere. Besides this, some part of organic matter of green plants contribute to the formation of coal deposition and rocks etc. By the during of the coal, oil, gas, plants and by the weathering of rocks of earth’s crust a part of co2 is also returned to the air.
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| Carbon cycle |
Hydrologic or Water cycle
Water covers about 73% of the earth surface in form of sea, lakes and rivers. From each of these water sources, water is consistently evaporated by the heat of sun. in atmosphere it condenses into clouds and finally returns to the surface of earth as rain, snow or hail. Water falling in this way runs into streams and rivers and ultimately returns back to the ocean. Some amount of water during rainfall percolates
into the deeper layers of earth. This water is picked up by the roots of plants and returned to the atmosphere through transpiration. Animal that eat plants have some of the plant water into their bodies. Animals return the water bank into atmosphere either by excretion or by evaporation.
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| Fig : Hydrogen Cycle |
Sedimentary cycle
Phosphorus Cycle : The major source of phosphorus are rock deposits. Through erosion and weathering inorganic phosphate becomes available to plants in dissolved condition. A good proportion of the available phosphate is washed into the sea. But from sea only a small fraction is returning to land system through man and certain sea birds. Phosphates from the soil taken by the producers. Consumers and
then to decomposers and made finally available for recycling through mineralisation and decomposition.
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| Fig : Phosphorus Cycle |