#### • Class 11 Physics Demo

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# Atmosphere Biosphere Hydrosphere Lithosphere

The region around and near the earth's surface can be divided into four interconnected geo-spheres. They are the lithosphere, hydrosphere, biosphere, and atmosphere. The life and material on or near the surface of the earth can be divided into four spheres. The names of these geo-spheres are derived from the Greek words. Litho means stone or rocky; atmo means air; hydro means water and bio means life.

Lithosphere
Lithosphere is the rocky, solid crust that covers the entire planet’s surface. This crust of the planet is inorganic and it consists of minerals. It covers the entire earth's surface and forms the basis of the mechanical properties of the earth.

There are two types of lithosphere:

Oceanic lithosphere - The oceanic lithosphere is associated with oceanic crust and it exists in the ocean basin.

Continental lithosphere - The continental lithosphere is associated with the continental crust.

Hydrosphere
The hydrosphere consists of all the water on or near the earth's surface. The hydrosphere includes the oceans, rivers, lakes, streams and also the moisture of the air. Most of the earth's surface is covered in water. About 97% of the earth's water is of the oceans. The remaining 3% is fresh water and $\frac{3}{4}$ of the fresh water is solid and exists in the form of ice sheets.

Biosphere
The biosphere comprises of the living system of the earth. It is composed of all the living organisms including plants, animals and single celled organisms. Life of the planet is found almost from three meters below the ground and about 30 meters above the surface and almost about 200 meters above the oceans and seas.  The biosphere is also known as the global sum of all the ecosystems. The biosphere integrates all the relationships, interactions of the living beings with the elements of the lithosphere, hydrosphere and atmosphere.

Atmosphere
Atmosphere comprises the air body that surrounds the earth. Atmosphere is located close to the surface of the earth and is dense at the surface. Atmosphere comprises of 79% of nitrogen gas and just 21% of oxygen and the remaining is carbon dioxide and other gases. The earth's atmosphere contains oxygen which is used by most of the organisms for respiration. The atmosphere also protects the living organisms from ultraviolet radiations emitted from the sun.