Page 157 - Science Class 07
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neither very heavy nor very light. The outer
surface of the earth had li le oxygen. Another
major element present on the earth was
hydrogen which reacted with the oxygen that
was there to form a small quan ty of water.
This went on over millions of years and when
ny plants come into being, they started giving
off oxygen through photosynthesis. So, the
quan ty of oxygen went on increasing thereby
forming more water. Animal need water for drinking.
WATER AND LIVING BEINGS Water also helps the bodies of animals to
We already know that every living being, have a maintain the temperature needed by them.
certain amount of water, fruits and vegetables. Also, water helps the wastes of the body to
come out of it. So, water is highly necessary for
Some figures are given below:
the human body. According to doctors, an adult
Human body = 65%
must drink 2.4 litres of water daily including the
Watermelon = 93% water that goes inside with various eaten
Elephant = 70% foods.
Cucumber = 93%
Water and Plants
Earthworm = 80%
Just like animals, plants also need water as
Tomato = 93%
their primary basic need to remain alive. We
Water and Animals also know that no seed can germinate without
Water is needed to help the body-process water.
smoothly. It dissolves the eaten nutrients and Moreover, plants make their food using soil-
helps it to flow easily through the diges ve solu on (formed in water) as a raw material in
channels and to pass into blood. the process of photosynthesis. The roots suck
We know well that water is the second primary water from the earth and send it to the leaves
need of the living beings. The reason is that the via the plant- ssue called xylem.
life on the earth began in water and it became Water and Economic Development
a basic need of living things. As for the animal
living in water, they feed on the nutrients Water is one of the most important natural
dissolved in water and breathe the oxygen resources. It is necessary not only for the
dissolved in it to remain alive. survival of the plants and animals. It is
necessary for agricultural as well as industrial
development.
Agricultural produc on depends on the
availability of water. However, different
agricultural crops need different amount of
water. Wheat crops need compara vely less
amount of water than the rice crops. But, no,
Animals living in water.
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