Chapter 14: NATURAL RESOURCES 9th

Chapter 14: NATURAL RESOURCES

1.       Life exists only on our planet - Earth.

2.       Life on Earth is dependent on many factors.

3.       Most life-forms need an ambient temperature, water, and food.

4.       The resources available on the Earth and the energy from the Sun are necessary to meet the basic requirements of all life-forms on the Earth.

What are these resources on the Earth?

1.       The natural resources on the land are, the water, soil and the air.

2.       The outer crust of the Earth is called the lithosphere.

3.       Water covers 75% of the Earth’s surface. It is also found underground. These comprise the hydrosphere.

4.       The air that covers the whole of the Earth like a blanket, is called the atmosphere.

5.       Living things are found where these three exist. This life-supporting zone of the Earth where the atmosphere, the hydrosphere and the lithosphere interact and make life possible is known as the biosphere.

6.       Living things constitute the biotic component of the biosphere.

7.       The air, the water and the soil form the non-living or abiotic component of the biosphere.

8.       Let us study these abiotic components in detail in order to understand their role in sustaining life on Earth.

The Breath of Life: Air

What is composition of air on Venus and mars? Why atmosphere of earth contains less carbon di-oxide?

1.       Air is a mixture of many gases like nitrogen, oxygen, carbon dioxide and water vapour.

2.       In planets such as Venus and Mars, where no life is known to exist, the major component of the atmosphere is found to be carbon dioxide.

3.       In fact, carbon dioxide constitutes up to 95-97% of the atmosphere on Venus and Mars.

4.       Eukaryotic cells and many prokaryotic cells need oxygen to break down glucose molecules and get energy for their activities.

5.       This results in the production of carbon dioxide.

6.       Another process which results in the consumption of oxygen and the concomitant production of carbon dioxide is combustion.

7.       This includes not just human activities, which burn fuels to get energy, but also forest fires.

8.       Despite this, the percentage of carbon dioxide in  our atmosphere is a mere fraction of a percent because carbon dioxide is ‘fixed’ in two ways:

(i)                 Green plants convert carbon dioxide into glucose in the presence of Sunlight called photosynthesis, and

(ii)                Many marine animals use carbonates dissolved in sea-water to make their shells.

What is The Role Of The Atmosphere In Climate Control?

1.       The atmosphere covers the Earth, like a blanket.

2.       Air is a bad conductor of heat.

3.       The atmosphere keeps the average temperature of the Earth fairly steady during the day and even during the course of the whole year.

4.       The atmosphere prevents the sudden increase in temperature during the daylight hours.

5.       During the night, atmosphere slows down the escape of heat into outer space.

6.       Think of the moon, which is about the same distance from the Sun that the Earth is.

7.       Despite that, on the surface of the moon, with no atmosphere, the temperature ranges from (Minus)

–190º C to 110º C.

8.       Thus atmosphere of the Earth maintains ambient temperature and thereby life is possible.

THE MOVEMENT OF AIR: WINDS

A.     What  causes the movement of air, and what decides

B.      Whether this movement will be in the form of a gentle breeze, a strong wind or a terrible storm?

C.     What brings us the welcome rains?

1.       Movement of air, terrible storm and rains all these phenomena are the result of changes that take place in our atmosphere due to the heating of air and the formation of water vapour.

2.       Water vapour is formed due to the heating of water bodies and the activities of living organisms.

3.       The atmosphere can be heated from below by the radiation that is reflected back or re-radiated by the land or water bodies.

4.       On being heated, convection currents are set up in the air. In order to gain some understanding of the nature of convection currents, the experiment given in the book could be performed.

Experiment:

a)       Place a candle in a beaker or wide mouthed bottle and light it.

b)      Light an incense stick and take it to the mouth of the above bottle.

c)       The way in which the smoke flow, when the candle is burning shows how air moves.

d)      The patterns revealed by the smoke show us the directions in which hot and cold air move.

What is the direction of wind during day and night? Why?

1.       When air is heated by radiation from the heated land or water, it rises. 
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