Everything which surrounds us may collectively be termed as the Environment.
The air which we breathe, the soil on which we stand, water, living and non-living things around, the environment, has influenced and shaped our lives since time immemorial. It is from the environment that we get food to eat, water to drink, air to breathe and all necessities of day to day life. Environment around us constitutes a life support system. Through a process of natural selection and elimination it is the environment only which has caused the evolution of the biological spectrum, the biosphere, as it exists today.
I. Basic Components of the Environment:
Environment consists of all living and non-living things which surround us. Therefore, the basic components of the environment are:
1. Atmosphere or the air 2. Hydrosphere or the water
3. Lithosphere or the rocks and soil 4. The living component of the environment or the biosphere
II. Atmosphere or the Air:
Atmosphere consists of a complex mixture of a number of gases, water vapour and a variety of fine particulate material. The gaseous mantle which surrounds the globe is constituted by about 5.15 x 1015 metric tons of gas which exerts a pressure of about 1 kg per sq.cm. on earth's crust (Sytnick 1985). Most of these gases are compressed in the lowermost layer. Pressure decreases as we move upward.
The composition of earth's atmosphere