the four realms of earth : lithosphere , hydrosphere , biosphere and atmosphere.
lithosphere : the outer most solid layer of the earth that is composed of rocks and soil is known as lithosphere.it is also called the crust of the earth.
hydrosphere:the hydrosphere contains all the water bodies in the world that cover about 71 per cent of the earth's surface.
biosphere : the biosphere is the narrow zone where the lithosphere , the hydrosphere and the atmosphere come in contact with one another.this realm contains all the living organisms found on the earth.
atmosphere : the atmosphere surrounds the earth as a layer containing a mixture of gases.it is held by the gravitational force of the earth.