Chapter 14: NATURAL RESOURCES

1.       The under-ground water and the water in rivers, lakes and ponds is also fresh.

2.       However, the availability of fresh water varies from place to place.

3.       Practically every summer, most places have to face a shortage of water.

4.       And in rural areas, where water supply systems have not been installed, people are forced to spend considerable amounts of time in fetching water from faraway sources.

Many municipal corporations are trying water-harvesting techniques to improve the availability of water, It is commonly called rain-roof water harvesting system or roof water recharging system, percolation ditches, open tree plantation etc. These techniques would increase the water by improved percolation and ground water recharge.

Why is water so necessary? And do all organisms require water?

1.       All cellular processes take place in a water medium.

2.       All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.

3.       Substances are also transported from one part of the body to the other in a dissolved form.

4.       Hence, organisms need to maintain the level of water within their bodies in order to stay alive.

5.       Terrestrial life-forms require fresh water for this because their bodies cannot tolerate or get rid of the high amounts of dissolved salts in saline water.

6.       Thus, water sources need to be easily accessible for animals and plants to survive on land.

What is the relationship between water and the life?

            In nature is there any relationship between the amount of available water and the number and variety of plants and animals that can live in a given area?

1.       There is a greater variety and abundance of life in a region that receives 5 cm of rainfall in a year or a region that receives 200 cm of rainfall in a year

2.       The map showing rainfall patterns in the atlas shows that States like Kerala, Assam, Himachal Pradesh, in India would have the maximum biodiversity, as they receive highest annual rainfall.

3.       And the states like Gujrat, Rajsthan, parts of Maharashtra etc would have the least.

4.       The availability of water decides not only the number of individuals of each species that are able to survive in a particular area, but it also decides the diversity of life there.

5.       Of course, the availability of water is not the only factor that decides the sustainability of life in a region.

6.       Other factors like the temperature and nature of soil also matter.

7.       But water is one of the major resources which determine life on land.

WATER POLLUTION

What is water pollution? What are causes? What are ill-effects? What are control measures?

“The undesirable changes in the quality of natural water are called as water pollution”.

1.       Water dissolves the fertilizers and pesticides that we use on our farms.

2.       So some percentage of these substances are  washed into the water bodies.

3.       Sewage from our towns and cities and the waste from factories are also dumped into rivers or lakes.

4.       Specific industries also use water for cooling in various operations and later return this hot water to water-bodies.

5.       Some industries like chemical, leather, distilleries etc throw their effluents directly into water bodies.

6.       Another manner in which the temperature of the water in rivers can be affected is when water is released from dams.

7.       The water inside the deep reservoir would be colder than the water at the surface which gets heated by the Sun.

8.       All this can affect the life-forms that are found in these water bodies in various ways.

9.       It can encourage the growth of some life-forms and harm some other life-forms.

10.   This affects the balance between various organisms which had been established in that system.

11.   So we use the term water-pollution to cover the following effects:

A.     The addition of undesirable substances to water-bodies. These substances could be the fertilizers and pesticides used in farming or they could be poisonous substances, like mercury salts which are used by paper-industries. These could also be disease-causing organisms, like the bacteria which cause cholera.

B.      The removal of desirable substances from water-bodies. Dissolved oxygen is used by the animals and plants that live in water. Any change that reduces the amount of this dissolved oxygen would adversely affect these aquatic organisms. Other nutrients could also be depleted from the water bodies.

C.      A change in temperature. Aquatic organisms are used to a certain range of temperature in the water-body where they live, and a sudden marked change in this temperature would be dangerous for them or affect their breeding. The eggs and larvae of various animals are particularly susceptible to temperature changes.

Mineral Riches in the Soil

1.       What is the soil and how is it formed?

2.       How is soil formed?

3.       What is soil erosion?

Chapter 14: NATURAL RESOURCES 9th

1.       But since land gets heated faster than water, the air over land would also be heated faster than the air over water bodies.

2.       So, if we look at the situation in coastal regions during the day, the air above the land gets heated faster and starts rising.

3.       As this air rises, a region of low pressure is created and air over the sea moves into this area of low pressure.

4.       The movement of air from one region to the other creates winds.

5.       During the day, the direction of the wind would be from the sea to the land.

6.       At night, both land and sea start to cool.

7.       Since water cools down slower than the land, the air above water would be warmer than the air above land.

How movement of air takes place?

1.       All the movements of air resulting in diverse atmospheric phenomena are caused by the uneven heating of the atmosphere in different regions of the Earth.

2.       But various other factors also influence these winds.

3.       They are the rotation of the Earth and the presence of mountain ranges in the paths of the wind is a couple of these factors.

RAIN

A.     How clouds are formed and bring us rain?

B.      What happens when air with a very high content of water vapour goes from a region of high pressure to a region of low pressure or vice versa?

1.       When water bodies are heated during the day, a large amount of water evaporates and goes into the air.

2.       Some amount of water vapour also gets into the atmosphere because of various biological activities.

3.       This air also gets heated. The hot air rises up carrying the water vapour with it.

4.       As the air rises, it expands and cools.

5.       This cooling causes the water vapour in the air to condense in the form of tiny droplets.

6.       This condensation of water is facilitated if some particles could act as the ‘nucleus’ for these drops to form around.

7.       Normally dust and other suspended particles in the air perform this function.

8.       Once the water droplets are formed, they grow bigger by the ‘condensation’ of these water droplets.

9.       When the drops have grown big and heavy, they fall down in the form of rain.

10.   Sometimes, when the temperature of air is low enough, precipitation may occur in the form of snow, sleet or hail.

11.   Rainfall patterns are decided by the prevailing wind patterns.

12.   In large parts of India, rains are mostly brought by the southwest or north-east monsoons.

13.   The ‘depressions’ in the Bay of Bengal causes rains in some areas.

AIR POLLUTION

A.     What is air pollution?

B.      What are causes of air pollution?

C.     What are hazards of air pollution?

D.     What are control measures?

E.      How is the quality of air affected and how does this change in quality affect us and other life forms?

“The undesirable change in the quality of natural air composition is called as air pollution”.

Causes:

1.       The fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur.

2.       When these fuels are burnt, nitrogen and sulphur too are burnt and this produces different oxides of nitrogen and sulphur.

3.       Not only is the inhalation of these gases dangerous, they also dissolve in rain to give rise to acid rain.

4.       The combustion of fossil fuels also increases the amount of suspended particles in air.

5.       These suspended particles could be un-burnt carbon particles or substances called hydrocarbons.

6.       Presence of high levels of all these pollutants causes visibility to be lowered, especially in cold weather when water also condenses out of air. This is known as smog and is a visible indication of air pollution.

Effects:

7.       Studies have shown that regularly breathing air that contains any of these substances increases the incidence of allergies, cancer and heart diseases.

8.       An increase in the content of these harmful substances in air is called air pollution.

Water: A Wonder Liquid

1. Why do organisms need water?

2. What is the major source of fresh water in the city/town/village where you live?

3. Do you know of any activity which may be polluting this water source?

What are the different forms of water available on earth?

1.       Water occupies a very large area of the Earth’s surface and is also found underground.

2.       Some amount of water exists in the form of water vapour in the atmosphere.

3.       Most of the water on Earth’s surface is found in seas and oceans and is saline.

4.       Fresh water is found frozen in the ice-caps at the two poles and on snow covered mountains. 

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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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