Title: "Natural Resources: Nurturing Our Planet's Precious Gifts"
Description:
"Natural Resources" is an illuminating ebook tailored specifically for Class 9 students studying biology. Embark on a captivating journey into the world of natural resources, discovering the invaluable gifts that our...
Chapter 14: “Natural resources”
KEY CONCEPTS : [ *rating as per the significance of concept]
CONCEPTS RATING
Breath of air **
A wonder liquid ***
Biogeochemical cycles *****
1. The” Biosphere” is the life supporting zone of the earthwith three sub-zones called as
lithosphere (rock part), atmosphere (air part)and hydrosphere (water part).
Breath of air
2. Composition of Air
3.The interactions between different components of the Biosphere to maintain the balance
between the biotic and a biotic component makes “Biogeochemical cycle”. Ex. Water
Cycle, Nitrogen Cycle, Carbon cycle, Oxygen Cycle,
4. Role of atmosphere in climate control : atmosphere act as protective blanket for the
earth. Since atmosphere is a bad conductor of heat, it keeps the average temperature of the
earth constant. At night, it slows down the escape of heat into outer space.
5. The movement of air : the atmosphere gets heated from the radiation that is reflected
back by the land or water bodies. As a result of heating, convection currents are set up in
the air. Since land gets heated faster than water, the air over land gets heated faster than
air above water bodies.
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, 6. In coastal regions, during the day, the air above the land gets heated faster and starts
rising. So a region of low pressure is created and air over sea moves into this area of low
pressure. The movement of air from one region to the other region causes Wind.
7. During the day, the direction of wind would be from the sea to the land and at night, both
land and sea starts to cool. Since water cools down slower than the land, the air above
water would be warmer than air above land, thus the direction of wind would be from the
land to the sea.
8. Air pollution : it is an undesirable change in the physical, chemical or biological
characteristics. It is caused due to an increase in the content of harmful substances
(pollutant) such as oxides of nitrogen and sulphur, etc.
9. Harmful effect of air pollution :
It affects the respiratory system causing breathing difficulties eg; bronchitis, asthma,
lung cancer, tuberculosis, etc.
Burning of fossil fuels like coal and petroleum releases oxides of nitrogen and
sulphur. Inhalation of these gases is dangerous.
Combustion of fossil fuel also increases the amount of suspended particles in air. The
presence of high levels of all these pollutants, reduce visibility in cold weather where
water also condenses out of air forming smog.
Acid rain formed from the gases like sulphur dioxide and nitrogen oxides present in
polluted air. It causes damage to living and non- living thing.
3. The Water Cycle:
a) The process in which water evaporates and falls on the land as rain and later flows back
into the sea via rivers is known as the “Water Cycle”. Water flows through rocks containing
soluble minerals, some of them get dissolved in the water. Thus the rivers carry many
nutrients from the land to sea and these are used by the marine organisms.
b) When the water vapors condense as water droplets and grow big and heavy, they fall
down in the form of “rain”. It ranges from 5 cm to 200 cm of rain fall in a year in our
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