Page 127 - SST Class 06

The atmosphere extends up to 1600 km. Its other. This narrow zone extends a few kilometres
density decreases with height. It is very dense at
the sea level and 80 percent of all gases are
present within 20 km of the Earth’s surface. The
atmosphere gradually merges with the space.
Air, like other matter, has weight. It exerts
pressure which is called atmospheric pressure . from very tiny organisms many of which we
This pressure is not uniform at all places. The air
tends to move from high pressure areas to low
pressure areas and this movement of air is called
wind .
Info Bits
Info Bits
Due to decreasing density of atmosphere,
mountaineers need oxygen cylinders to climb up
high hills.
Quiz Time
Write True or False :
1. The air is made up of different gases. ________
2. A sea is not a vast water body. ________
3. There are four oceans on the Earth. ________
4. About 91 percent of the Earth’s surface is
covered with water. ________
5. The atmosphere extends up to 1600 km.
________
BIOSPHERE
You have studied the domains of lithosphere,
hydrosphere and atmosphere. Life cannot exist in
any one of them, though all of them are
favourable for it. This is the blending of all these
three domains that life can start and sustain. The
place where these three domains blend is called
the domain of biosphere.
Life originates in the narrow zone where all three
of land, water and air come into contact with each
v The lithosphere comprises of land masses and ocean beds.
v Land constitutes about 29 percent of the total Earth’s surface.
above and below the Earth’s surface. This is the
contact of these three domains together that the
Earth becomes a unique planet. This zone, known
as the biosphere, supports a massive variety of
organisms, both plants and animals. We can find
cannot see by the naked eye, to the largest
organisms in this zone. There are about one
million species of animals and over three lakh
species of plants. These species live in the water,
on the land and in the air.
Balance of Biosphere
This topic is all the more relevant in the present
times as much harm has been caused to the
delicate balance of the three domains. Man
dominates all other species of animals and plants.
He wants to live a lavish life, consuming as much
as he can. This greedy tendency has resulted in
the destruction of the biosphere. He has destroyed
a large number of species of animals and plants
for his greed. But this tendency has resulted in
adverse effect to the biosphere. If this continues
any longer, the very existence of the biosphere
may be at risk; it means that the very survival of
man may be jeopardised severely. So, we have to
take notice of this destruction and reduce our
needs, if we want our children to continue to live
as we do today.
Biosphere
Major Domains of the Earth
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