The term 'Environment' is derived from the French word 'Environner' which means to encircle or surround or encompass. All the biotic and abiotic components surrounding an organism are thus included in environment. Environment means conditions which influence the growth and development of organisms. It commonly means surroundings. In this way, "environment is the sum total of water, air and land, inter-relationships among themselves and also with the human beings, other living organisms and property." This important definition given in Environment Act, 1986 clearly states that environment includes all the physical and biological surroundings and their interactions. The close interaction between the organisation and the environment is important in order to satisfy the basic necessities to life. Every thing organism depends on the environment for energy, water, oxygen, food, shelter and mates. Hence, everything influencing the life processes of an organism constitutes it's environment.
The elements of environment are:
(a) Air: The envelope of air that surrounds the earth is called the atmosphere. It extends upto about 900 KM above the earth. It consists of various gases and water vapour. It is composed of nitrogen (78.09%), oxygen (20.94%), carbon dioxide (0.03%), argon ( 0.93%), neon (0.002%), helium (0.0005%), krypton (0.0001%), xenon (0.00001%), other rare gases and a variable quantity of water vapour.
Air controls life on the earth. It is a storehouse of oxygen needed by man and other animals and of carbon dioxide essential for green plants. Without air, there would be no clouds, no winds, no rain, no snow, and no fire. As a matter of fact, there would be no life on this globe.
(b) Water: Water is regarded as the essential liquid substance for life on the earth. Water is vital to life. It is said that life was first originated in water and it is absolutely essential for all forms of life. No life can survive without water. We drink water, bathe in it, wash clothes in it, fish in it, irrigate the plants, produce energy with it and also use water for transportation and recreation. Most of the ancient civilizations have grown and flourished in river valleys of the Nile, Indus, Tigris and Euphrates etc. Even now water resources provide a foundation for social, cultural and economic development.
Water is the chief component of environment which covers nearly three- quarters of the earth's surface forming the oceans, seas, lakes, ice- sheets etc. Most of the surface water is found in the world oceans like the Pacific, Atlantic, Indian, Antarctic and the Arctic. The water in oceans cannot be used for drinking and domestic purposes for its high quantity of salt. The major part of fresh water with a salt content of 0.2% is found either in still water like ponds and lakes or running water in the forms of streams and rivers. Fresh water is also available in the form of rain, ice, snow and few. Thus the sources of usable or freshwater are very limited and major part of the water on the earth is saline, i.e. salty.
(c) Soil: soil is the outermost solid crust of the Earth. Hills, mountains, plateaus and the plains are the parts of the continental regions. Soil is made up of dust, sand, clay and organic substances. Soil may be defined as "any part of earth's crust in which plants roots." It is usually formed as a result of long-term process of complex interactions between climatic, biological and topographic factors.
Soil is one of the most important ecological factors for the survival of living organisms including man. It is very essential for life air and water. Plants depend on soil for their nutrients, water and essential minerals. Soil contains organic substances known as humus which is found in the top layer of the soil. Microbes fertilize the soil. They break up the nutrients of the soil into small parts, which the plants are capable of absorbing. Soil without microbes becomes less productive. Soil provides a habitant for all living beings including micro- organisms, plants, animals and man. In this way, all living organisms depend directly on soils. The prosperity of human beings depend largely on fertile soil. Therefore, fertile soil is regarded as the most important natural resource. The nutrients in the soil are usually regenerated by decay and decomposition of organic substances deposited by the micro- organisms. Such micro- organisms are the sources of soil fertility. But when these organisms are destroyed, then soil tend to cause their degeneration, loss of fertility and increase the rate of soil erosion.
