THE PHYSICAL ENVIRONMENT

  THE PHYSICAL ENVIRONMENT

By

Prof .M.THANGA DARWIN

                        It is also known as a biotic environment and natural environment. The meaning of ‘a-biotic’ or ‘physical’ is non-living like land water air conditions atmosphere which constitutes of soil. So, we can say that physical or a-biotin environment is the environment which includes non-living or physical things which are constitutes of soil and affect the living things.    The physical or a-biotin environment also includes the climatic factors such as sunbeams, rainwater, precipitation, moisture, pressure and wind speed.

1. Atmosphere:

The thick, gaseous cover of air surrounding the earth is called atmosphere. It sustains life on earth by removing harmful cosmic and ultraviolet rays through absorption, maintaining heat balance, providing oxygen for respiration and carbon dioxide for photosynthesis. It is the gaseous envelope surrounding the earth and extends up to 500 km above the earth’s surface. The composition of the atmosphere is given in Table.

The Structure of the Atmosphere

                         The atmosphere is broadly divided into four major zones viz. Troposphere, Stratosphere, Mesosphere and Troposphere.

              Troposphere: Troposphere is the layer of air nearest to the ground. Temperature decreases with height. The average temperature drops from 15ºC at sea level to –56.5ºC at 11 km above sea level. It contains 70% of the atmosphere’s mass. The density of the troposphere decreases with altitude. The air near the ground level is heated by the radiation from earth, but the temperature decreases uniformly with altitude. this decrease of temperature with altitude is known as lapse rate. Tropopause is the top of the troposphere, which is a transition layer between Troposphere and Stratosphere.

         Stratosphere: Stratosphere is the layer of air above the troposphere where temperature increases with height. The average temperature rises to –2.5ºC at 50 km above sea level. Ozone is found in higher concentrations between 20 and 30 km above the surface. Hence sometimes this layer is referred to as the “ozone layer”. Ozone absorbs radiant energy from the sun and hence warmer temperatures are encountered in the stratosphere. Stratosphere is the top of the stratosphere, which is a transition layer between Stratosphere and Mesosphere.

2. Mesosphere:

Mesosphere is the layer of air above the stratosphere where temperature decreases with height. The average temperature decreases to –90°C at 90 km. This is the coldest layer of the atmosphere. Mesopause is the top of the mesosphere, which is a transition layer between Mesosphere and Thermosphere.

3. Troposphere: Troposphere is the layer of air above the mesosphere. The temperatures in the troposphere increase with increasing height, but there are not many molecules in this layer. The air becomes less and less dense as we reach space.

4.  Hydrosphere: This comprises all water resources both surface and ground water. The world’s water is found in oceans and seas, lakes and reservoirs, rivers and streams, glaciers and snow-caps in the Polar Regions in addition to ground water below the land areas. The water locked up in the Oceans and Seas are too salty and cannot be used directly for human consumption, domestic, agriculture or Industrial purposes. Only less than 1% of water resources are available for human exploitation.

5. Lithosphere: The upper layer of the earth's crust is called lithosphere. It is made up of soil, minerals, rocks and other organic as well as inorganic matter. The lithosphere covers the crust of the earth and is extended up to 100 km.

The Importance of Physical Environment

• ·      Just think, the most important thing to make house is residential space, and for residential space, we need land area. The land area is included in physical environment. So it is responsible for the residential for living beings.
• ·     The a-biotic environment like soil, water and air are the necessary nutrients element provider for the living beings.
• ·     All of living beings are surrounded by atmosphere; it is the combination of different types of gases. The living beings take oxygen and other gases from the atmosphere.
• ·        The a-biotic environment also controls the climatic factors like weather.
• ·    The physical environment also includes the soil which is responsible for the works and food crops for the living beings. It also provides diverse types of minerals which are very necessary for growth of life Water is one of the most necessary things for living beings. Physical environment also deals with the water factor of the earth.

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