Presence of water
(1) The earth looks blue when it is seen from space. Many astronauts have
taken photographs of the earth from space.
(2) All these photograph
which is covered about 70% of vwater.
(3) It means three parts of the earth is covered with water and only one par
looks blue in colour. It is due to the earth surface is land.
(4) Water is one of the most abundant natural resources.
(5) It has been estimated that total amount of water present on earth is
about 1.33 billion cubic kilometers which covers nearly 80 percent of the earth.
The oceans contains 97%of worlds water .the rest of the water is in rhe form of glaciers ice caps grounds water and inland water.
The inland water include reiver lakes streams and soil moisture .
The atmoshphere also contains water in the form of vapour.
a) The sun shines on the oceans lakes, ponds and river streams. It also
shines every where on land,
g The heat of the sun vapouries water These vapours rise in the
atmosphere and form clouds constant. called the water cycle.
mcontin oustransfen of water betweer different reservoirs on the earth is
The wind drifts these clouds to colder region where tiny drops of water
are formed due to condensation.
(4) These droplets get converted into bigger drops and even may freeze to
snow and fall on the ground as rain and snow.
(5) This rain and snow once again joins the streams, rivers, lakes and
oceans. Some water also get absorbed in the ground.
(6) In this way, the total quantity of water on our earth remains almost
to the leaves, where photosynthesis take place.
(5) Leaves have stomata at their lower surface from where excess water is
released in air in the form of vapours. The process is known as transpirati
WATER IN LIVING ORGANISMS:
(Animals and plants all need water to live. The bodies of animals and
plants contain 50% to 80% water.
(2) The human body contains about 35-50 litres of water. Every day about
2-5 litres are lost through sweet, breathing and excretion.
(3) Thus it is important to drink water to replace the daily loss of water from
(4) Plants absorb water from the soil with their roots. Roots transport wate