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Nutrient Cycles

The movement of nutrient elements through various components (abiotic and biotic)...

The movement of nutrient elements through various components (abiotic and biotic) of an ecosystem is called nutrient cycling or biogeochemical cycle.

Carbon cycle
  1. Carbon constitutes 49 per cent of dry weight of an organism.

  2. 71 per cent of the carbon is found dissolved in oceans which is responsible for its regulation in atmosphere.

  3. The carbon cycle occurs through atmosphere, oceans and through living and dead organisms.

  4. It is estimated that 4 x 1013 kg of carbon is fixed in the biosphere through photosynthesis annually.

  5. Carbon is returned to atmosphere as C02 by animals and plants through respiration and the activities of decomposers.

  6. Some amount of fixed carbon is lost as sediments and removed from circulation.

  7. Burning of wood, forest fire, volcanic activity and combustion of organic matter and fossil fuels are some essential sources for releasing C02 in the atmosphere.

  8. Human activities like deforestation and vehicular burning of fossil fuels has caused an increase in the amount of C02 in atmosphere.

Phosphorus Cycle
  1. Importance of phosphorus:

    It is a major constituent of biological membranes, nucleic acids and cellular energy transfer systems. It is required for making shells, bones and teeth.

  2. Rocks are the natural reservoirs of phosphorus.

  3. During weathering of rocks, minute amounts of these phosphates dissolve in soil solution and are absorbed by plant through roots.

  4. Herbivores and carnivores obtain this element from plants directly or indirectly.

  5. The waste products and the dead organisms are decomposed by phosphate-solubilising bacteria and in turn release phosphorus.

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