Notes for UPSC-Biosphere, Lithosphere, Hydrosphere, Atmosphere, Motion of the Earth and Weather and Climate

Biosphere

1. The part of the Earth where life exists is called the Biosphere ('bios' means 'life').
2. The Earth is the only planet of the solar system that supports life. Life is possible because of its unique lithosphere, hydrosphere and atmosphere.

Lithosphere

1. The uppermost layer of the Earth's crust which is capable of supporting life is called Lithosphere.
2. The Lithosphere (or land) covers two-sevenths or 29.22% (14,90,41,182 sq. km.) of the total surface area of the earth.

Hydrosphere

1. Hydrosphere (or sea) covers five-sevenths or more accurately 70.78% (36,10,59,226 sq. km.) of the total surface area of the earth.
2. Water is freely available in the gaseous, liquid and solid state.
3. It is necessary for carrying out chemical reactions within the bodies of the living organisms.
4. Water also dissolves and transports nutrients from the soil to the plants.
5. It is used by plants for making food.

Atmosphere

1. The envelope of air that completely surrounds the earth is known as atmosphere.
2. The atmosphere extends to about 1000 km from the surface of the earth. But 99% of the total mass of the atmosphere is found within 32 km.
3. This is because the atmosphere is held by the gravitational pull of the earth.

Motion of the Earth

1. The Earth spins (rotates), west to east on its axis once in 24 hours approximately.
2. The Earth's axis is not vertical. It makes an angle of 23° 30' with the vertical or 66° 30' with the plane of the. Earth's orbit.
3. The Earth's axis always remains pointed in the same direction (towards the Pole Star) as the Earth moves around the Sun. The tilt of the Earth's axis is known as the inclination of the Earth's axis.

Weather and Climate

1. Weather is the description of the atmospheric conditions of a particular place at a particular time for a short period of time.
2. Climate is the composite or integrated picture of the weather conditions over a long period of time.
3. Climatic data is based on calculated averages of data recorded over a period of 35 years. The classical period is 30 years, as defined by WMO.