What is Oxygen Cycle?

The oxygen cycle is the biogeochemical transitions of oxygen atoms between different oxidation states in ions, oxides, and molecules through redox reactions within and between the spheres and reservoirs of the planet Earth. Processes within the oxygen cycle are considered to be biological or geological and are evaluated as either a source (O2 production) or sink (O2 consumption). It helps in maintaining the oxygen level by moving through three main spheres of the earth which are:

  • Atmosphere: The atmosphere is 20.9% oxygen by volume, Other oxygen-containing molecules in the atmosphere include ozone (O3), carbon dioxide (CO2), water vapor (H2O), and sulfur and nitrogen oxides.
  • Lithosphere: The lithosphere is 46.6% oxygen by volume present mainly as silica minerals (SiO2) and other oxide minerals.
  • Biosphere: The biosphere is 22% oxygen by volume present mainly as a component of organic molecules (CxHxNxOx) and water molecules.
  • Hydrosphere: The hydrosphere is 33% oxygen by volume present mainly as a component of water molecules with dissolved molecules including free oxygen and carbonic acids (HxCO3).

This biogeochemical cycle explains the movement of oxygen gas within the atmosphere, the ecosystem, biosphere, and lithosphere. The oxygen cycle is interconnected with the carbon cycle. The atmosphere is the layer of gases presents above the earth’s surface. The sum of Earth’s ecosystems makes a biosphere. The lithosphere is the solid outer section along with the earth’s crust and it is the largest reservoir of oxygen.
Oxygen Cycle

Stages of the Oxygen Cycle

The steps involved in the oxygen cycle are:

Stage-1: All green plants during the process of photosynthesis, release oxygen back into the atmosphere as a by-product.

Stage-2: All aerobic organisms use free oxygen for respiration.

Stage-3: Animals exhale Carbon dioxide back into the atmosphere which is again used by the plants during photosynthesis. Now oxygen is balanced within the atmosphere.

Importance of Oxygen Cycle

As we all know, oxygen is one of the most essential components of the earth’s atmosphere. It is mainly required for:

  • Breathing
  • Combustion
  • Supporting aquatic life
  • Decomposition of organic waste.

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