User:Theodore Sangeeth

= Atmosphere = The envelope of air which surrounds the earth is called Atmosphere. The presence of atmosphere has made the earth unique planet. It has life giving gases like oxygen, carbondioxide, helium, ozone, argon, hydrogen e.t.c., we all know that without air life is impossible. In other words we can say atmosphere plays a major role in Human's life. An atmosphere is nothing but full of air. It helps not only for human beings but also for plants and animals.

Considering the size of the earth, the atmosphere is a relatively thin layer. It's exact thickness is unknown, as there is no sharp boundaries between the atmosphere and outer space. It is estimated that upper limit of the atmosphere is at a height of about 10,000 Km from the mean sea level. Atmosphere is held to the earth due to its gravitation pull. The air is denser near the earth surface and gets thinner as one goes upwards.

Composition of Atmosphere:
Nitrogen      -   78%

Oxygen       -   21%

other gases -   1%

Nitrogen
It is the most important and dominant gas in the atmosphere. It is required by plants for growth. Bacteria in the soil and roots observe and changes it form so that plants can use it.

Oxygen
It is the second most important gas all living organism need it to survive. It is also helpful for combustion. During photosynthesis green plants observe carbondioxide and release oxygen.

Other gases
These gases helps one or some other way for living and non-living organisms