OXYGEN CYCLE
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The oxygen cycle is the constant interaction between biotic and abiotic component that helps in the circulation of oxygen in the atmosphere, biosphere and lithosphere.
Occurrence of Oxygen:
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Oxygen is a very abundant element on our Earth. It is found in different forms like elemental, oxides, organic compounds etc.
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Elemental form: Molecular form of oxygen [O2] is found in atmosphere [21%] and as dissolved oxygen in hydrosphere.
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Oxides: it occurs in the air in the form of carbon dioxide while in the crust as the oxides of most metals and also as carbonate, sulphate, nitrate and other minerals.
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Organic compounds: Oxygen is an essential component of most biological molecules like carbohydrates, proteins, nucleic acids and fats.
Processes involved in oxygen cycle:
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When oxygen cycle is referred the level of atmospheric oxygen is considered which is maintained by various processes that consumes and releases the oxygen from / in the atmosphere.
Consumption of Oxygen from atmosphere:
Combustion:
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Burning of fuels or forests in the presence of oxygen release carbon dioxide hence depletes the level of atmospheric oxygen.
Respiration:
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An essential life process by which living organisms inhales oxygen and oxidizes glucose to release energy from it for various body functions.
Formation of oxides of nitrogen:
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Nitrogen is an essential part of living forms but is not consumed directly from atmosphere. For this it has to be first converted into oxide and then it is incorporated into living world. This oxidation of nitrogen occurs in different ways by biotic and abiotic components.
Release of Oxygen in atmosphere:
Photosynthesis:
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Oxygen is returned to the atmosphere in only one major process, i.e., photosynthesis. During photosynthesis, carbon dioxide [air] and water [soil] reacts to form glucose. Water splits into hydrogen ions and oxygen, H+ reacts with CO2 and oxygen is released into the environment.
Representative diagram of oxygen cycle:
