Environmental Studies (EVS)
The study of environment is a multi dimensional activity. It seeks to create public awareness about environmental problems among public at large. It studies the resources and the problems arising out of their degradation. Degraded environment directly affects society. It, thus involves the study of such issues as environmental ethics, social pollution etc.
Environment means our surrounding which refers to the biosphere. The biosphere is considered as a thin shell of many hundred kilometers of radius that encapsulates the earth. All forms of life, both living and non-living organisms evolve and exist within the biosphere. The life substaining resources such as air, water, food etc. are recycled within the biosphere. Waste products are also cycled through the biosphere.
According to the definitional dictionary of geography, environment is the "Sum total of all the surrounding conditions that envelop an organism or community or an object".
Our environment includes everything around us. They may be grouped into the following organisms.
1) Abiotic (non-living) environment such as
(a) air, (b) water, (c) soil.
2) Biotic (living) environment such as
(a) mankind, (b) birds, (c) animals.
All these constituents of environment are referred to as the environmental factors or ecological factors. An environmental factor is defined as " ecological condition which directly or indirectly affects the growth and development and life of an organism".
Environment is made up of three segments namely,
(1) Atmosphere, (2) Hydrosphere, (3) Lithosphere
1. Atmosphere
It is a blanket of suspended liquids, solids and gases that envelop the earth. It extends beyond the earth surface up to many hundred kilometers. The presence of life on earth is attributed to atmosphere which is the prime source of the following matters.
i . Oxygen (O2) which is essential to animal life.
ii. Carbondioxide (CO) which is essential for plants for photosynthesis
iii. Functioning of wind, rain, snowfall etc.
iv. Formation of clouds, weather and climate.
Atmosphere comprises many gases and water vapour which is called air. Main gases in lower atmosphere near the earth surface are nitrogen. oxygen, Carbondioxide, argon, etc. These gases are found in varying amounts at different heights in atmosphere. They are mainly thick upto 1 km elevation. This thickness is termed as boundary layer. This is the normal height limit of layer breathing air for existence of life.
Structure of atmosphere
The atmosphere extends vertically upto several thousand kilometers in space. It has no defined boundary with outer space. Air gradually becomes rare to rarer as we move up vertically in space. Various ecological factors such as temperature, pressure, moisture, light etc. go on changing as we move up in atmosphere. The atmosphere has five different layers that are determined by the changes in temperature that happen with increasing altitude.
1. Troposphere: Troposphere extends upto an average altitude of 11 kilometers from the earth surface. This is the densest area which contains about 75% of the total atmospheric mass. Formation of clouds, storms, etc. occur in this region. The base of this layer is warmer than its top because the air is heated by the surface of the earth.
2. Stratosphere: Stratosphere lies above the Troposphere and extends upto an average altitude of 50 kilometers. The main activity in this zone is absorbtion of ultra violet radiation by ozone.
3.Mesosphere: Mesosphere extends upto an average altitude of 87 kilometers above the stratosphere. The main activity in this region is burning of meteorites and their disintegration. As the mesophere extends upward above the stratosphere, temparature decreases. The coldest parts of the atmosphere are located in this layer which even goes upto -90°C.
4. Thermosphere: Thermosphere extends upto an average altitude of 500 kilometers above the mesosphere. The main activity in this region is the high kinetic energy of gas molecules. The thermospehere is very sensitive to solar activity and can heat utpo 1500°C or higher.
5. Exosphere: It is the upper most layer of atmosphere where atoms and molecules escape into space.
3. Lithosphere
It is the top crust of the earth. The ocean basin and continents lay on it. The crust thickness varies widely, being thickest in continental regions (about 40 km) and thinnest in the ocean basins (about 10 to 12 km). The upper most layer of soil on earth crust is the most important region of lithosphere. It is because the major biological activities occur in this region. It contains organic matter and is the source of producing food for animal and human beings.
Also the major biological activities and decomposition of organic wastes is carried out by a host of micro organisms in soil.
