As far as we know, our earth is the only planet where life exists, though scientists su constantly searching for signs of life on other heavenly bodies. You have already learlt: ii the previous block, how life came into existence on this planet. You have also studied, that several hundred million years ago, living conditions on the earth were quite different from what they are today and so were the earlier living organisms. The present variety of animals and plants has evolved out of the old ones just as the present living conditions on the earth have evolved over a period of rhillions of years. In addition to sunlight, air, soil, water, the eanh has got the right pressure and temperature that enables life to exist, evolve, and diversify. Actually there exists a very delicate balance in nature between the earth's environment and the living organisms. If this balance is disturbed then the life that exists (day is likely to be affected or even destroyed. Flash floods.andsoi1 erasion are same of the adverse effects of this imbalance. Therefore, we must understand that how living and non-living things exist in harmony with nature and what aie the processes that maintain this balance. In this unit you will learn how life system is sustained on this planet.
As already mentioned earlier, it is made up of basically two types of components: living and nun-living. The living components include various types of plants, frogs, birds, fish, turtle, insects and numerous kinds of microscopic life forms called microbes.