SNC1D
Biosphere Zones
Composition of Earth’s Environment :
Atmosphere : It is the gaseous envelope that surrounds the earth. Its major components are Nitrogen (
78% ), Oxygen ( 20.96% ), Argon ( 0.93% ), Carbon-dioxide ( 0.032% ), and other inert gases. The earth's
environment can be divided in four major zones or layers
Composition of Atmosphere
Troposphere Stratosphere Mesosphere Thermosphere

Troposphere: The zone immediately above the surface of the earth is called the Troposphere.
Its height extends up to 20km above the equator and 8 km above the poles. 75% of the

Atmosphere's mass is found in the Troposphere.
Stratosphere: The layer above the Troposphere is called the stratosphere. It extends upto an
attitude of 50km. The temperature in this region increases slowly due to absorption of ultraviolet
radiations. This layer is an important zone of the Atmosphere at it contains the Ozone layer. The
Ozone layer protects the Earth from the Harmful ultraviolet rays that come from the sun which

have a potential to cause destruction to living beings/life and property.
Mesosphere: It is a zone above the Stratosphere with thickness of about 40km and

extends upto 85km from the surface of the earth.
Thermosphere: This zone lies above the Mesosphere where temperature increases with
height. Most of the constituents in this zone are in an ionized state.
Hydrosphere: The Hydrosphere includes all the water bodies existing in liquid state above and below
the surface of the earth. Water is the medium in which all the bio-chemical reaction within a living
organism and a large number of chemical reactions within a living organism and a large number of
chemical reaction involving components of rocks, soils, and pollutants of environment occur. The
availability of water determines the nature, composition, and abundance of terrestrial life. Regions within
very low rainfall become deserts while on the other hand lush green vegetation develops in regions of
abundant water supply.
SNC1D
Biosphere Zones
Lithosphere: The earth's crust consists of rocks and soils made up of different chemical elements and
minerals.
Biosphere: The biosphere is the living component of the environment. It forms a thin crust of living
beings spread over the surface of the earth and constitutes all its states of living system the existences of
well being of living organism ( micro and macro ) depend on a system of complex interaction within and in
between the components of environment ( lithosphere hydrosphere and biosphere ).
Source:
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