Natural resource of Class 9

Air is an important form of inexhaustible natural resource which is essential for our survival. In a world without air, there would be no plant or animal life; no fire as burning needs oxygen; no protection from harmful solar radiation; and great temperature variation (from about 110° C at day time to about – 184°C at night).

Composition of Air:

Component         Volume

Nitrogen (N2)

Oxygen (O2)

Carbon dioxide (CO2)


Trace components*






Besides these gaseous components air also possesses water vapour, industrial gases, dust, smoke particles, microorganisms, pollen grains, fungal spores etc.

Different Regions of Atmosphere

Region    Range of distance    Density of Air    Importance

Troposphere    10–12 kms from the    Highest    Most of the atmospheric air is present

surface of earth        here. It is a medium for locomotion of flying animals, helps in dispersal of seeds and fruits; region of cloud formation.

Stratosphere    12–60 kms    Less than    Contains ozone layer that traps most

troposphere    of UV rays and cosmic rays of the sun.

Mesosphere    60–100 kms    Low    —

Thermosphere    100 kms upwards    Extremely low    Reflect radio waves back to earth, artificial satellites are present here.

At a height between 15 kms and 60 kms, there is a layer of ozone gas in the upper atmosphere. This ozone layer is very important for the existence of life on earth. This is because ozone layer absorbs most of the harmful UV radiations coming from the sun which can otherwise cause inflammatory diseases, skin cancer, cataract etc. A normal human being requires about 250 to 265 kg air per day for performing various activities.

Importance of Air

Air is essential for the survival and continuity of life as its constituents are needed for various biological processes.

Role of Gases

The various gases present in the air have different functions. They are:

  • Respiration: The correct proportions of nitrogen and oxygen are required for respiration. In the cell, the oxygen oxidizes sugar molecules to produce carbondioxide and water, and liberates energy. The carbon dioxide is expelled out and the energy is used to perform various activities.
  • Burning: The oxygen of air is essentially required for burning of things like wood, fuels, organic wastes, etc. When they burn in air, carbondioxide and water vapour are produced with the release of heat energy.
  • Forest fire: It consumes a lot of oxygen.
  • Photosynthesis: Green plants convert carbondioxide to glucose in the presence of sunlight.
  • Formation of shells: Many marine animals use carbonates dissolved in sea water to form their shells.

The role of air in climate control

Air is a bad conductor of heat. The atmosphere (envelope of air) acts as a protective blanket for living organisms in the following ways:

  •  Air plays a very important role in keeping the temperature of the Earth fairly steady during the day and even during the course of whole year. This happens as a result of a phenomenon known as the green house effect.
  • Certain gases like carbon dioxide, methane, etc. called green house gases prevent the sudden increase in temperature during the day and slows down the escape of heat during the night. The situation on the moon is quite different which is about the same distance from the sun as the Earth. Moon has no atmosphere and the temperature ranges from – 190°C to 110°C.

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