ATMOSPHERE COMPOSITION AND STRUCTURE

Earth is a unique planet because the life is found only on this planet. The air has a
special place among the conditions necessary for life. The air is a mixture of several
gases. The air encompasses the earth from all sides. The air surrounding the
Earth is called the atmosphere. The atmosphere is an integral part of our Earth. It
is connected with the earth due to the gravitational force of the earth. It helps in
stopping the ultra violet rays harmful for the life and maintain the suitable temperature
necessary for life.
    The air is essential for the survival of all forms of life on the earth. You cannot
imagine any kind of life in the absence of it. The atmosphere is like a large protective
cover. Besides many gases, water vapor and dust particles are also found in the
atmosphere. Due to these all kinds of changes take place in the atmosphere you
will study in this lesson. The composition and structure of the atmosphere and the
cyclic process of main gases.

COMPOSITION OF ATMOSPHERE

The atmosphere is made up of different types of gases, water Vapor and dust
particles. The composition of the atmosphere is not static. It changes according to
the time and place.
(A) Gases of the atmosphere:
The atmosphere is the mixture of different types of gases, including water
vapor and dust particles. Nitrogen and Oxygen are the two main gases of
the atmosphere. 99 percent part of it is made up of these two gases. Other
gases like organ, carbon dioxide, hydrogen, neon, helium etc. form the
remaining part of atmosphere 

Ozone Gas

The amount of ozone gas in the atmosphere is very little. It is limited to the ozone
layer but it is very important. It protects the living beings by absorbing the ultraviolet
rays of the sun. If there was no ozone gas in the atmosphere, there would
not have been existence of living beings and plants on the earth surface.

(B) Water vapour

Gaseous form of water present in the atmosphere is called water vapour. Water
vapour present in the atmosphere has made life possible on the earth Water vapour
is the source of all kinds of precipitation. Its maximum amount in the atmosphere
could be upto 4 percent. Maximum amount of water vapour is found in hot-wet
regions and its least amount is found in the dry regions. Generally, the amount of
water vapour goes on decreasing from low latitudes to high latitudes.
In the same way, its amount goes on decreasing with increasing altitude. Water
vapour reaches in the atmosphere through evaporation and transpiration.
Evaporation takes place in the oceans, seas, rivers, ponds and lakes while
transpiration takes lace from the plants, trees and living beings.

(c) Dust Particles

Dust particles are generally found in the lower layers of the atmosphere. These
particles are found in the form of sand, smoke and oceanic salt. Sand particle have
important place in the atmosphere. These dust particles help in the condensation
of water vapour. During condensation water vapour gets condensed in the form of
droplets around these dust particles. Due to this process the clouds are formed
and precipitation is made possible.

Importance of the Atmosphere:

(i) Oxygen is very important for the living beings.
(ii) Carbon dioxide is very useful for the plants.
(iii) Dust particles present in the atmosphere create suitable conditions for the
precipitation.
(iv) The amount of water vapour in the atmosphere goes on changing and directly
affects the plants and living beings.
(v) Ozone protects all kinds of life on the earth from the harmful ultra violet rays
of the sun.  MORE