Among the nine planets of the solar system, with is the only one where life exists. Plants and animals exist on earth because it has all the favorable conditions required for survival of life.
Even on earth life is not found everywhere because survival requires a particular type of environment. That part of the earth where plants and animals exist is called biosphere. Biosphere is further divided into three parts; lithosphere, hydrosphere and atmosphere. Lithosphere is that part of earth where rocks, sand, soil, plants, animals, etc. are found. That part of the earth where water is present is called hydrosphere. All the animals and plants need water to live. The blanket of air which surrounds the earth up to a height of about 100 km is called atmosphere. Atmosphere is a balanced mixture of several gases like nitrogen, oxygen and carbon dioxide. The major atmosphere extends up to 320 km above lithosphere and hydrosphere. About 10 km below and 10 km above the surface of the earth is biosphere. In reality 90 percent living beings live in the area between 1 km below and 1 km above the earth’s surface.
Biosphere or ecological frame work always remains in a dynamic equilibrium. In this many biological and physical elements are present in a balanced state. Air, water, soil, animal, plants and bacteria are all linked to each other or to their surroundings by some means or the other. This system is called environment. Environment includes all those conditions which affect our life. Plants, animals, water, air, land are important parts of our environment because living being cannot survive without them. Our houses, villages, towns etc. all are included in the environment. Man has created an imbalance in the environment by its haphazard exploitation to fulfill his needs. The trees are being cut mercilessly; water and air are becoming highly polluted. If environmental pollution keeps on increasing with the present rate, the very existence of the life on earth is endangered.