Natural Resources Notes

• Carbon cycle is a constant interaction between biotic and abiotic components of the earth by which carbon is exchanged between the various geological systems of the earth and its atmosphere. The carbon keeps circulating between the four carbon reservoirs.

Occurrence:

• Carbon exists in different forms on the earth.

• 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:

• Oxygen is a very abundant element on our Earth. It is found in different forms like elemental, oxides, organic compounds etc.
• Elemental form: Molecular form of oxygen [O₂] is found in atmosphere [21%] and as dissolved oxygen in hydrosphere.
• 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.
• Organic compounds: Oxygen is an essential component of most biological molecules like carbohydrates, proteins, nucleic acids and fats.

• Ozone (O₃) is a molecule formed by three atoms of oxygen, shields the surface of the earth (in the stratosphere) from ultraviolet (UV) radiation of Sun. (O₃) in the troposphere is a pollutant, as it is harmful for the living organisms.

Ozone layer Depletion:

• Ozone layer is a layer made up of ozone molecules shielding our atmosphere near the stratosphere which prevents the entry of UV rays of sun into earth’s surface.