Four realms of the earth
Our earth is a unique planet in the whole solar system, It is the only planet which is habitable and which supports life, Though some times it is supposed that conditions on the Mars, another planet in the solar system, are also favourable to support some form of life, yet there is no evidence to sustain it. Land, water and air are the major domains of the earth which sustain life. The land mass or the solid crust of rock is called the Lithosphere, The vast water mass which includes oceans and seas is called the Hydrosphere. The domain of air that surrounds the earth is called the Atmosphere.