JKBOSE 9th Class Science Solutions Chapter 15 Natural Resources

JKBOSE 9th Class Science Solutions Chapter 15 Natural Resources

JKBOSE 9th Class Science Solutions Chapter 15 Natural Resources

Jammu & Kashmir State Board JKBOSE 9th Class Science Solutions

J&K class 9th Science Natural Resources Textbook Questions and Answers

◆ Life exists on planet Earth only.
◆ Life on earth depends upon surrounding temperature water, energy and food.
◆ The resources on earth are equally important. The most important requirement is the solar energy.
Environment is the surroundings of an organism and influences its life.
◆ The environment is the sum total of all the components both from living and nonliving ones.
◆ The living or biotic components include plants, animals and microorganisms whereas non-living or abiotic or physical components consists of air, water, soil, light and temperature.
◆ All components are closely interrelated and interdependent on each other, lead to a balance environment.
◆ The habitat of plants and animals greatly vary.
Natural resources. It is the stock of nature such as air, water, soil, coal, minerals, animals and plants that are useful to mankind in many ways.
◆ Natural resources include total natural environment.
Inexhaustible resources are present in plenty and cannot be exhausted by man’s by consumption.
◆ Stock of exhaustible natural resources in the nature is limited and will finish sooner or later.
Air is an important form of inexhaustible natural resource which is essential for our survival.
◆ Composition of Air
Nitrogen (N2) —   78%
Oxygen (O2) —   21%
Carbon dioxide (CO2) —   0.03%
Argon —   0.9.%
Helium, Neon, Ozone, Ammonia — 0.04%
Helium, Argon and Neon are noble – gases.
◆ Lithosphere. It is the outer crust of Our Planet, the Earth.
◆ Hydrosphere. It is the portion of the earth’s surface covered with water which is about 75 percent-comprising of seas, oceans, rivers, streams, lakes, ponds, etc.
◆ Atmosphere. It is the multilayered gaseous envelope of air that covers the whole of Our planet Earth like a blanket.
Atmosphere plays important role in control of climate, movement of air (winds) and rain.
◆ Biosphere. It is the life supporting zone of the Earth where the atmosphere, the hydrosphere and the lithosphere interact and make life possible. It occupies the highest position or level in the hierarchy of organisation on the earth.
◆ Water is an important medium for all the life processess and acts as a universal solvent and termed ‘wonder liquid’.
Water covers 75% of earth’s surface.
The upper level of the zone of saturation is called water table.
The oceans, rivers, streams, lakes, ponds, pools, polar ice caps, water vapours constitute hydrosphere.
◆ Soil is another main natural resource essential for our survival and development.
◆ Soil forms the upper surface of the land and supports plant growth.
Wind and rain causes soil erosion by carrying away the top loose soil particles.
Rain causes soil erosion on unprotected top soil by washing it down.
Deforestation also leads to soil erosion.
Our underground reservoir of metals and minerals are limited.
◆ Minerals are non-renewable exhaustible resources.
◆ The renewable sources of energy are regenerated naturally within a short span of time eg. plants, animals, sun light etc.
◆ Non-renewable sources of energy take millions of years to form like the coal, lignite, petroleum and natural gas.
◆ Air Pollution. It is an undesirable change in the physical, chemical or biological characteristics of air. It is caused due to an increase in the content of harmful substances (air pollutants) in air such as oxides of nitrogen and sulphur, etc.
The major sources of air pollution are burning of fossil fuels like coal and petroleum, automobiles, thermal power plants and industries.
◆ Pollution of air, water and soil affect quality of life and harm biodiversity.
◆ Water Pollution is contamination of water of rivers and lakes with unwanted and harmful substances. Water is said to be polluted when there is any physical, biological or chemical change in its quality that adversely affects living organisms and makes it unfit for use.
The balance in the environment including the flow of energy and matters is also supported by various living beings by acting as producers and consumers.
◆ Hydel power is next biggest source of energy after thermal power.
The term flora is used for plants and fauna for animal species.
The Forests provide timber for building and furniture along with raw material for paper industry.
The natural resources should be used rationally, equitably and keeping in mind their replaceability.
◆ Biosphere is considered to be the largest biological system.
All the ecosystems taken together in a given geographical area having the same type of climate is called biome.
◆ Biomass literally means living matter in any organism.
◆ Ozone layer. Ozone is a triatomic gas with a molecular formula O3 which is present in the upper reaches of the atmosphere (in the stratosphere region).
◆ Ozone layer prevents the harmful radiations of sun from reaching the surface of earth, where they may damage many forms of life.
◆ CFCs (Carbon compounds with both fluorine and chlorine) are damaging the ozone layer, thus the danger of increasing in UV rays on earth will enhance.
⇒ NGO. Non-governmental organisations.
⇒ IUCN. International Union For Conservation of Nature and Natural Resources.
CO₂ forms 95-97% of atmosphere on venus and mars.
On Moon temperature ranges from -190°C to 110°C.
Smog formed by smoke and fog is visible indication of air pollution.
⇒ Biosphere. The part of earth and its atmosphere that is inhabited by living organisms.
Air, water and soil form the non-living or abiotic component of the biosphere.
⇒ Atmosphere. It is a transparent gaseous envelope surrounding the earth.
Water covers 75% of earth’s surface.
⇒ Environment. Living organisms and their surroundings constitute the environment.
Ecology. It is the study of reciprocal relationship between the living organisms and their environments.
⇒ Terrestrial. The organisms found on land.
⇒ Habitat. The surrounding or the locality in which an organism lives in nature.
⇒ Soil. The fertile surface layer of the earth capable of supporting plant growth is called soil.
⇒ Fertility of soil. The capacity of the soil to sustain plant life with required nutrients is called fertility of soil.
⇒ Garbage energy. The energy produced from urban garbage.
⇒ Nuclear energy. It is generated by fission or fusion of the atoms of certain elements like uranium.
Biosphere is considered to be largest biological system.
Our underground reservoir of metals and mineral are limited.
Q. 1. How is our atmosphere different from atmosphere on Venus and Mars ?
Ans.— In planets such as Venus and Mars the major component of atmosphere is 9597% of CO₂ and it does not support life. Atmosphere on planet Earth is a mixture of nitrogen (78.08%), oxygen (20.95%), CO₂ (0.03%) and water vapours that help life to exist on earth.
Q. 2. How does atmosphere act as a blanket ?
Ans.— Atmosphere acts as a blanket because of following reasons :
1. Air is a bad conductor of heat.
2. The atmosphere keeps the average temperature of earth fairly steady during the day and even during the course of whole year.
3. The atmosphere prevents the sudden increase or decrease in temperature.
Q. 3. What causes winds ? 
Ans.— All movements of air are caused by the uneven heating of the atmosphere in different regions of earth. Air above the land gets heated faster and being light starts rising. As the air rises, a region of low pressure is created. Due to this, air over the sea moves into this area of pressure.
Factors which control movement of wind
1. The rotation of earth and presence of mountain ranges are other factors which cause winds.
2. Uneven heating of land in different parts of earth.
3. Differences in heating and cooling of land and water.
Q. 4. How are clouds formed ?
Ans.— Clouds are formed by the condensation of water droplets in air. It occurs as large amount of water evaporates and goes into air. Air rises up, it expands and cools. The cooling causes the water vapours in the air to condense in the form of tiny droplets. These water droplets get bigger by more and more condensation of other droplets and form clouds.
Q. 5. List any three human activities that you think should lead to air pollution.
Ans.— 1. Combustion of fossil fuels. Excessive use and burning of fossil fuels like coal and petroleum by man in industries and automobiles produces different oxides of nitrogen and sulphur. These are not only dangerous to our respiratory system but also leads to acid rain.
2. Deforestation i.e. cutting of trees leads to deterioration of atmosphere. The pollutants also come from industries.
3. Forest fires, excessive mining and ore refining, excessive use of chloro-fluorocarbons and excessive industrialisation leads to air pollution.
Q. 6. Why do organisms need water ?
Ans.— Importance of water.
1. All cellular processes take place in water medium.
2. All 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. Organisms need to maintain the level of water within their bodies in order to survive.
5. Water is universal solvent and helps the organism in many ways.
6. Water is required by organisms for many of their activities such as agriculture, production of hydro power, drinking, cooking etc.
7. Terrestrial life forms require fresh water because their bodies cannot tolerate high amount of dissolved salts in saline water.
8. The availability of water is the major resource which determines the diversity of life on land.
9. Thus, water is essential for maintenance and very existence of life.
Q. 7. What is the major source of fresh water in the city/town/village where you live ? 
Ans.— Fresh water is found in ice-caps and on snow covered mountains. The underground water and the water in rivers, lakes and ponds is also fresh. This water is available for human use.
Q. 8. Do you know any activity which may be polluting the water sources ?
Ans.— 1. Sewage from towns and cities and waste from factories released into water bodies.
2. Discharging hot water from cooling towers into water bodies act living organisms.
Q. 9. How is soil formed ?
Ans.—The breaking up of rocks at or near the surface of earth over long period of time result in soil formation. They are broken down by various physical, chemical and biological processes. The end products of this breaking down are the fine particles of soil.
Soil. There are many other factors which play a vital role in the formation of soil.
These factors are :
1. The Sun. It causes heating of rocks which causes cracking and ultimately breaking up into smaller pieces.
2. Water. It breaks rocks both by freezing and fast flow.
3. Wind. It causes erosion of rocks.
4. Living Organisms. Lichens and mosses growing on rock surface form cracks in them and result in their breakdown.
Q. 10. What is soil erosion ?
Ans.— Removal of useful components from the soil which affect fertility of soil is called soil erosion.
Q. 11. What are the methods of preventing or reducing soil erosion ?
Ans.— Prevention of of Soil F Erosion
1. It can be prevented by intensive cropping.
2. It can be prevented by providing proper drainage canals around the fields.
3. Soil erosion in hilly areas can be prevented by practising terrace farming.
4. It can be prevented by planting trees and sowing grasses.
5. It can be prevented by constructing strong embankments along the river banks.
Q. 12. What are different states in which water is found during water cycle ?
Ans.— Ground water, surface water, water vapours, water droplets, clouds. Water is found in gaseous state, liquid state and solid state during water cycle.
Q. 13. Name two biological important compounds that contain both oxygen and nitrogen.
Ans.—Proteins and Nucleic acids (DNA and RNA).
Q. 14. List any three human activities which would lead to an increase in CO₂ of air.
Ans.— 1. Industries due to burning of fuel.
2. Combustion of fossil fuel to provide energy for various needs like heating, cooking transportation etc.
3. Respiration and Deforestation.
Q. 15. What is greenhouse effect ? 
Ans.— Greenhouse effect. The increase in global temperature due to rise in CO₂ is called greenhouse effect. It causes global warming.
Q. 16. What are two forms of oxygen found in the atmosphere ?
Ans.— 1. Oxygen (0₂), about 21%.
2. Ozone. In the upper region such as stratosphere oxygen is found in the form of ozone.
Q. 1. Why is atmosphere essential for life ?
Ans.— Importance of atmosphere. 
1. Role of atmosphere in climate control. Atmosphere acts as blanket and keeps the average temperature of earth steady during day and even during course of year.
2. Movement of air causes winds.
3. Rain and rainfall pattern are decided by wind pattern.
4. Air provides oxygen for breathing.
5. Water is essential for life.
6. Atmosphere absorbs rays thus protects living organisms.
Q. 2. Why is water essential for life ?
Ans.— Importance of water. ‘Water is wonder liquid and essential for life’ due to the roqmos listser to avoms following reasons’ :
(i) Life is not possible without water.
(ii) Water makes up 60-70 per cent of body weight.
(iii) All the reactions that take place in our body and within the cells occur between substances that are dissolved in water.
(iv) Water is required for transport of materials.
(v) The density of water is similar to that of protoplasm.
(vi) Water is a universal solvent.
Q. 3. How are living organisms dependent on the soil ? Are organisms that live in water totally independent of soil as a resource ?
Ans.— Functions of Soils.
1. Soil plays an important role in plant growth by providing water, nutrients and anchorage i.e. fixation of plant in it.
2. Soil also supports the growth of crops, grassland and forests which provide us food, fibre, wood and building material.
3. Soil is important resource and decides the diversity of life in an area. Plants living in water are not independent of soil.
Q. 4. You have seen weather reports on television and in newspapers. How do you think that we are able to predict the weather ?
Ans.— Weather can be predicted on the basis of the study of following :
1. Movement of air resulting in diverse phenomena caused by uneven heating of the atmosphere in different regions of the earth.
2. Rainfall pattern is decided by the prevailing wind pattern.
Q. 5. We know that many human activities lead to increasing levels of pollution of the air, water bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution ?
Ans.— Pollution of air, water and soil is caused by human activities such as :
1. Combustion of fossil fuels for energy used for industries, automobiles.
2. Further use of insecticides and fertilizers cause pollution of soil and water.
3. Release of chemicals from industries also cause pollution.
4. If separate industrial zones are created, it will help in reducing pollution.
5. Controlled release of pollutants from automobiles.
Q. 6. Write a note on how forests influence the quality of our air, soil and water resources.
Ans.— 1. Roots of plants have in important role in preventing soil erosion.
2. Forests have moderating effects on climates.
3. Forests prevent floods.
4. Forests release O₂ evolved during photosynthesis into atmosphere, thus renewing the oxygen.
Q. 1. What is air pollution ? Write the main sources and preventive measures.
Ans.— Air Pollution. Air pollution refers to the release into the atmosphere of materials The that are harmful to man, other animals, plants and buildings or other objects.
Sources of Air pollution
The major sources of air pollution are fossil fuels (coal and petroleum) and industries.
Human Sources. Many activities done by man are the main sources of air pollution. These activities can be divided into following categories.
1. Combustion activities.
2. Industrial activities.
3. Agricultural works.
4. Use of solvents.
5. Activities concerned with atomic energy.
Preventive measures for air pollution.
To prevent and control air pollution two types of measures can be adopted.
1. Instead of releasing poisonous gases containing various pollutants into the atmosphere they could be destroyed or used by some other measures.
2. Converting harmful pollutants to harmless products and then releasing them into the atmosphere.
Q. 2. List two control measures for minimising air pollution.
Ans.— Control measures for minimising air pollution.
1. Simple combustible solid wastes should be burnt in incinerators.
2. Automobiles must be either made to eliminate the use of gasoline and diesel oil or complete combustion is obtained in the engine so that harmful products are omitted.
Q. 3. Explain the process responsible for soil formation.
Ans.— Processes for soil formation.
1. The Sun. The sun heats up rocks during the day so that they expand. At night, the rocks cool down and contract. The unequal expansion and contraction in different parts of the rock results in the formation of cracks and ultimately rocks break up into smaller pieces.
2. Water. Water helps in the formation of soil in two ways : (i) Water could get into the cracks in the rocks formed due to uneven heating by the Sun. If this water freezes, it will widen the cracks.
(ii) Fast flowing water carries big and small particles of rock downstream, causing breakdown of rock particles into smaller, finer particles through their abrasive effects.
3. Wind. Strong winds also break down rocks. They also carry sand from one place to the other like the water does.
4. Living organisms. They also influence the formation of soil. While lichens grow on surface of rocks, they release certain substances that cause the rock surface to powder down and form a thin layer of soil. Likewise, small plants like moss and roots of big trees also break the rocks.
Q. 4. List various measures for soil conservation.
Ans— Soil conservation. 
1. Stopping clear-cutting of forests and overgrazing of ranges check soil erosion by streams and rivers.
2. Intensive cropping helps in checking soil erosion. A field always under a crop is protected against erosion.
3. Bunds around the fields contain rain water and check soil erosion besides washing away of minerals.
4. Irrigation channels in the fields should be so designed as to carry water at a slow speed.
5. Drainage canals to carry flood water will protect the fields against erosion.
Q. 5. How will you determine composition of soil ?
Ans.— Determination of Soil Composition. Materials required. 150 cc of sifted soil, a measuring glass cylinder of 1 litre capacity, water, glass rod.
Procedure. Take 150 cc of sifted soil in a glass or tur cylinder. Pour about 750 cc of water over it. Stir the soil well with the help of a glass rod. Take out the rod. Allow the particles to settle. Observe after 30 minutes.
Results. The bottom of the cylinder has a layer of coarse sand. A layer of fine sand lies above it. Then there is a layer of silt. Clay lies above silt. Turbid water occurs above the clay. It contains clay as well as mineral salts. Humus or organic matter floats over the top of turbid water.
Q. 6. Make an outline sketch of Nitrogen cycle.
Ans.— Nitrogen Cycle.
Q. 7. What are the causes of ozone depletion ?
Ans.— Ozone depletion. Recently it was discovered that this ozone layer was getting depleted. Various man-made compounds like CFCs (carbon compounds having both fluorine and chlorine which are very stable and not degraded by any biological process) were found to persist in the atmosphere. Once they reached the ozone layer, they would react with the ozone molecules. This resulted in a reduction of the ozone layer and recently they have discovered a hole in the ozone layer above the Antarctica. It is difficult to imagine the consequences for life on Earth if the ozone layer dwindles further, but many people think that it would be better not to take chances. Measures should be taken towards stopping all further damage to the ozone layer.
Q. 1. List the factors on which life is dependent on earth.
Ans.— Factors. 1. Ambient temperature, water and air.
2. Resources available on earth.
3. Energy from sun.
Q. 2. What is biosphere ? What are the main sub-divisions of the biosphere ?
Ans.— Biosphere. The entire inhabitated part of earth and its atmosphere including the living components is called biosphere.
The three main sub-divisions of biosphere are hydrosphere, lithosphere and atmosphere.
1. Hydrosphere. It includes all the water components of oceans, seas, river and other inland water.
2. Lithosphere. It comprises the solid components of the earth’s crust which support life.
3. Atmosphere. It is formed of gaseous cover which envelops the hydrosphere and lithosphere.
Q. 3. What is atmosphere ? Name its different layers.
Ans.— Atmosphere. Gaseous envelope surrounding the earth is called atmosphere. Several concentric layers can be identified in vertical profile of atmosphere. Density, temperature and composition differ in these layers. Near the earth’s surface, density is highest and with increase in latitude density decreases. Starting from earth’s surface five concentric layers can be distinguished :
1. Troposphere 2. Stratosphere 3. Mesosphere 4. Thermosphere 5. Ionosphere.
Exosphere which forms the outer fringe of atmosphere is highly rarefied and gradually get mixed with other space.
Q. 4. Write the composition of dry atmosphere.
Ans.— Composition of dry atmosphere.
Components Volume
Nitrogen (N₂) 78%
Oxygen (O₂) 21%
Carbon dioxide (CO₂) 0.03%
Argon 0.93%
Helium, Neon, Ozone, ammonia 0.04%
* Helium, Neon and Argon are noble gases.
Q. 5. What are biotic components of atmosphere ?
Ans.—Plants, animals and micro-organisms.
Q. 6. What are abiotic components of atmosphere ?
Ans.— Abiotic Components. There are many non-living things like air, water, soil, light and temperature around us and form physical environment. They affect all the living organisms to a great extent and have very important role in their growth, development and even in the survival. For example, the plants need light, water and air (CO₂) for photosynthesis. Animals need food, water and air (O₂) for their survival. All these physical components together form environmental conditions which can be referred as weather and climate of a particular area. Soil provides the support for many plants and animals.
Q. 7. How is balance maintained in the environment ?
Ans.— The living or biotic components are plants and animals including us and nonliving or physical components are air, water, soil, light and temperature. All these components interact and effect each other, resulting in the establishment of a complex and complete balance in the environment. The environmental components like mountains, rivers, ponds, forests, minerals, coal and even petrol and other natural resources are of great importance for us.
Q. 8. How is CO₂ fixed in atmosphere ? 
Ans.— CO₂ is fixed in two ways :
1. Green plants convert CO₂ into glucose in the presence of sunlight and chlorophyll pigments.
2. Many marine animals use carbonates dissolved in sea water to make their shells.
Q. 9. What for oxygen is required by eukaryotic and many prokaryotic cells ?
Ans.— All the cells need oxygen to break down glucose molecules in order to release energy required to carry out this vital functions of life.
Q. 10. What is the role of atmosphere in climate control ?
Ans.— Role of atmosphere in climate control. Atmosphere covers the earth like a blanket. Air is a bad conductor of heat. The atmosphere keeps the average temperature of the earth fairly steady during the day and even during the course of the whole year. The atmosphere prevents the sudden increase in temperature during the daylight hours.
During the night, it slows down the escape of heat into outer space. Moon, which is about the same distance from the Sun that the Earth is. Despite that, on the surface of the moon, with no atmosphere, the temperature ranges from -190° C to 110° C.
Q. 11. What is the role of atmosphere in movement of air which causes winds ?
Ans.— The Movement of air causes winds.
1. The atmosphere gets heated from the radiation that is reflected back or re-radiated 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 the air above water bodies.
2. 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 winds.
3. 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 the air above land, thus the direction of wind would be from the land to the sea.
Q. 12. How are rainfall patterns decided ?
Ans.— 1. Rainfall patterns are decided by the prevailing wind patterns.
2. In large parts of India, rains are mostly brought by the south-west or north-east monsoons.
3. Depressions’ in the Bay of Bengal have caused rains in some areas is the common comment during weather reports.
Q. 13. What is the role of atmosphere in causing rain ?
Ans.— Role of atmosphere in causing rain.
1. When water bodies are heated during the day, a large amount of water evaporates and goes into the air.
2. The wind carries the water vapour to various places.
3. The air gets heated and rises up carrying the water vapour with it.
4. As this air rises, it expands and cools causing the water vapour in the air to condense in the form of tiny droplets.
5. Once the water droplets are formed, they grow bigger by the ‘condensation’ of these water droplets.
6. When the drops grow big and heavy, they fall down in the form of rain.
Q. 14. Write a note on the air pollution caused due to combustion.
Ans.— The mobile combustion sources are the main sources of air pollution especially in the cities. They include the locomotives, automobiles and aircrafts.
The air pollutants from these are :
1. (i) Carbon monoxide (ii) oxides of nitrogen and (iii) a mixture of hydrocarbons.
2. If the petroleum used as fuel in these sources contains lead as an impurity in the form of tetraethyl lead Pb (C₂H5)4 and tetramethyl lead Pb (CH3)4
Q. 15. Discuss harmful effects of air pollution.
Ans.— Harmful Effects of Air Pollution.
1. Air pollution affects the respiratory system causing breathing difficulties and diseases such as bronchitis, asthma, lung cancer, tuberculosis and pneumonia.
2. Burning of fossil fuels like coal and petroleum releases oxides of nitrogen and sulphur. Inhalation of these gases is dangerous. These gases also dissolve in rain to give rise to acid rain.
3. The combustion of fossil fuel also increases the amount of suspended particles in air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons. The presence of high levels of all these pollutants, reduce visibility in cold weather where water also condenses out of air forming smog. Smog is an indication of air pollution.
4. Regular breathing in the polluted air increases of allergies, cancer and heart diseases.
Q. 16. What is smog ?
Ans.— Smog. Smoke and fog make smog in the presence of sunlight, various unburnt hydrocarbons produced from the automobile combustion react with oxides of nitrogen to form ozone, peroxyacyl nitrates and aldehydes. They are called photochemical oxidants. Together with smoke and fog they constitute smog which has a harmful effect on humans repiratory and nervous system; it also harms the plants and rubber goods.
Q. 17. List a few disorders caused by air pollution. 
Ans.— 1. Allergies 2. Cancer 3. Heart diseases.
Q. 18. What are aerosols ?
Ans.— Aerosols. Aerosols are certain chemicals released in the air with force in the form of mist or vapour. The important source of aerosols is the jet aeroplane emissions in the outer atmosphere. The aerosols contain fluorocarbons which deplete the ozone layer in atmosphere.
Q.19. What are acid rains ?
Ans.— Acid Rain. It is the rain which contains small amount of acid in it that is formed from the gases like sulphur dioxide and nitrogen oxides present in polluted air. It causes damage to living and non-living things.
Q. 20. What are the uses of ground water ?
Ans.— (i) It provides moisture for plant growth.
(ii) It is used for human consumption.
(iii) It supplements water in streams.
(iv) It is required for irrigation purposes.
Q. 21. What are the methods of conservating water resource ?
Ans.— (i) Treated water should be provided for irrigation purposes.
(ii) Water should be used carefully and economically for domestic and industrial purposes.
(iii) Dams should be built for storage of flood water.
(iv) Top soil is maintained to check soil erosion.
(v) Flood control.
(vi) Artificial recharging of ground water.
Q. 22. What is water pollution ?
Ans.— Water pollution. Addition of harmful materials to water is termed water pollution. The sources of inland water pollution are community waste water (sewage) and wastes from industries and agricultural practices. Water pollutants include organic matter, pathogens, chemicals and minerals, solid particles, radioactive wastes and heat.
Q. 23. What are the sources of water pollution ?
Ans.— Sources of water pollution.
1. Agriculture substances such as fertilisers and pesticides are used to increase crop yield, and some amount of these chemicals is washed into the water bodies that pollutes the water.
2. Sewage from homes and wastes from factories are dumped into rivers or lakes also cause water pollution.
3. Hot and cold water discharged from industries make a change in temperature, which is harmful for aquatic organisms.
4. All these affects the balance among various organisms that are found in water bodies.
Q. 24. What are the effects of water pollution ?
Ans.— Effects of Water Pollution.
1. Water pollutants reach the sea directly from the coastal cities and ships, and indirectly with river water from distant places. Oil spilled in tanker accidents is a major threat to ocean life.
2. The substances like fertilisers and pesticides used in farming, mercury salts used by paper industries could be poisonous. There could also be disease-causing organisms, like the bacteria which causes cholera.
3. Industrial or household waste reduces the dissolved oxygen in water bodies, thereby affecting the aquatic life.
4. Aquatic organisms can stay alive in a certain range of temperature. Sudden change in temperature of water bodies is dangerous for aquatic organisms and affects their breeding.
Q. 25. Make a list of various diseases caused by polluted water.
Ans.— Diseases caused by polluted water.
1. Bacterial diseases. Cholera, Typhoid, Diarrhoea, Dysentery.
2. Viral diseases. Jaundice, Polio etc.
3. Protozonal diseases. Diseases associated with stomach and intestines e.g. Amoebic dysentery, Giardiasis etc.
4. Helminthic diseases. Infection of some intestinal parasites like Ascaris lumbricodies is through drinking water only. Guinea worm diseases is through Cyclops present in the drinking water. Through contaminated water they reach to another host i.e. man.
Q. 26. Why is soil as resource important for mankind ?
Ans.— Soil is a rich source of minerals and humus. It is important for growing of crops. Soil water is used by plants for various functions.
Soil provides support to crops, grassland and forests thus it is an important natural resource.
Q. 27. Define soil fertility. How can it be maintained ?
Ans.— Soil fertility. It is the ability of soil to provide minerals, water and other nutrients to plants.
Conservation of Soil fertility
1. Adding of manure to the soil.
2. Rotation of crops
3. Keeping the land as such without growing any crop.
4. Addition of fertilizers.
Q. 28. Write few artificial methods to maintain soil fertility.
Ans.— (i) Nitrogeneous and other fertilizers are added.
(ii) For natural restoration of nutrients, soil is kept uncultivated for certain period.
Q. 29. Describe the role of humus.
Ans.—(i) Humus increases the soil fertility.
(ii) Humus has high retaining capacity for water.
(iii) It makes the soil porous and allows water and air to penetrate deep.
Q. 30. Discuss the role of wind and living organisms in soil formation.
Ans.—Role of wind in the soil formation. Strong wind rubs against rocks and wear them down. The wind also carries soil particles from one place to other.
Role of living organisms in soil formation.
Living organisms also influence the formation of soil. The lichen that we read about earlier, also grows on the surface of rocks. While growing, they release certain substances that cause the rock surface to powder down and form a thin layer of soil. Other small plants like moss, are able to grow on this surface now and they cause the rock to break up further. The roots of big trees sometimes go into cracks in the rocks and as the roots grow bigger, the crack is made bigger.
Q. 31. Why step farming is common in hills ?
Ans.— As the hills have steep slopes and soil erosion is caused by water currents. Thus step farming help in checking soil erosion.
Q. 32. Why are root nodules useful for plants ?
Ans.— Root nodules are where nitrogen fixing bacteria Rhizobium live. They have symbiotic relationship with plants. These bacteria fix this atmospheric nitrogen into nitrates and nitrites. These can be absorbed by plants, and thus soil fertility also increases in this way.
Q. 33. Lichens are called pioneer colonies on bare rock. How can they help in formation of soil ?
Ans.— Lichens release acidic substance which break down the soil into small particles thus leads to formation of soil. It is termed weathering of rocks.
Q. 34. What are the effect of use of fertilizers and pesticides for long period on soil fertility ?
Ans.— Effects of use of fertilizers and pesticides.
1. Use of these substances over long periods of time can destroy the soil structure by killing the soil micro-organisms that recycle nutrients in the soil.
2. They also kill the earthworms which are instrumental in making the rich humus.
3. Fertile soil can quickly be turned barren if sustainable practices are not followed.
4. Major cause of soil pollution is removal of useful components from the soil and addition of other substances, which adversely affect the fertility of the soil and kill the diversity of organisms that living it, is called soil pollution.
Q. 35. Write a few properties of water. Sketch water Cycle.
Ans.— Water is a liquid at room temperature. It is densiest (heaviest) at about 4°C. The dense water sinks and the lighter frozen water (ice) floats, ice also insulates the water below. This enables the aquatic life to survive under the ice in cold weather.
Water Cycle
Q. 36. Make a simple line sketch to show nitrogen cycle in the biosphere.
Ans.— The nitrogen cycle in the biosphere involves the following steps :
Q. 37. What is Carbon ? Make a diagram of Carbon Cycle.
Ans.— Carbon Cycle. Series of processes by which carbon compounds are inter-converted in the environment, involving the incorporation of carbondioxide into living tissue and its return to the atmosphere through respiration, the decay of dead organisms and burning of fossil fuels is called carbon cycle.
Q. 38. List the various forms in which carbon is present.
Ans.— Forms of Carbon. Carbon is found in various forms on the earth.
1. It occurs in the elemental form as diamonds and graphite.
2. In the combined state, it is found as carbon dioxide in the atmosphere, as carbonate and hydrogen-carbonate salts in various minerals.
3. All life-forms are based on carbon-containing molecules like proteins, carbohydrates, fats, nucleic acids and vitamins.
4. Both plants and animals release carbon dioxide to the atmosphere as a product of respiration.
5. By decomposition of organic wastes and dead bodies by decomposers.
6. By burning of fossil fuels, like coal, and petroleum.
Q. 39. Make simple sketch to show oxygen cycle in nature.
Ans.— Oxygen cycle
Q. 40. To protect a forest means to conserve air, soil and water. Explain.
How do forests influence the quality of air, soil and water resources ? 
Ans.— The forest is a complex biological system. Though it is self-sufficient, it depends on the other renewable resources to maintain itself. Therefore to protect a forest it is necessary to conserve air, soil and water. A forest relies on specific climatic conditions for its survival. At times, large scale man-made geographical alterations such as huge dams and excessive mining have disturbed the environment of the region causing severe damage to the forests in the area. Air pollution from industries situated even miles away have similar ill effects on the forests.
Q. 41. What is Greenhouse effect? Show the % age of gases that cause greenhouse effect.
Ans.— Greenhouse effect. Earth’s temperature is maintained by re-radiated infra-red radiations by CO₂, CH4 O3, NO and NO2 and slightly by water vapours in atmosphere. These gases prevent heat from escaping to outer space, so are functionally comparable to glass panels of a greenhouse and are called greenhouse gases (GHGs) and called as greenhouse effect. The CO₂ is added to atmosphere mainly by burning fossil fuels, volcanic activities and respiration.
Q. 42. What is Ozone layer ? Write its importance.
Ans.— Ozone layer. It is the protective layer. Ozone in stratosphere is responsible for protecting the earth from high energy ultraviolet radiations. It forms a life-saving screen as it checks the entry of lethal UV- rays. Ozone found in troposphere has warming effect. Ozone is one gas which is harmful as well as useful for human beings. 16th September, 1996 was celebrated as “International Day for the Preservation of Ozone layer”. It was aimed to generate awareness about the dangers of ozone depletion in the stratosphere and it was drawn up by UNEP.
Q. 43. What is meant by ozone shield? How the CFC’s and ozone substances effect Ozone shield ?
Ans.—Ozone shield. An equilibrium is established between generation and destruction of O3, leading to a steady state concentration of ozone layer in the stratosphere between 20 and 26 km above the sea level. The thickness of the vertical column of stratospheric O3 layer, condensed to standard temperature and pressure, average 0.29 cm above the equator and may exceed 0.40 cm above the poles at the end of the winter season. This layer acts as the ozone shield protecting the earth biota from harmful effects of strong UV radiation.
CFC’s produce active Chlorine (C1 with CO radical) in presence of UV radiations. These radicals catalytically destroy ozone converting it into oxygen. CH4 and N₂O also cause ozone destruction.
Q. 44. What is the environmental significance of the increasing Antarctica ozone hole ?
Ans.— Effects of UV radiations on human. In humans, the increased UV radiation increases the incidence of cataract, and skin cancer (including melanoma) and diminishes the functioning of immune system.
Q. 1. What is environment ?
Ans.— Environment. The earth and everything which affects the living organisms constitute its environment.
Q. 2. Define habitat.
Ans.— The habitat of an organism is the place where it lives.
Q. 3. What are the different types of habitat of organisms ?
Ans.— (i) Terrestrial (land) (ii) aquatic (water) and (iii) aerial (air).
Q. 4. What are biotic components ?
Ans.— Biotic components means other living beings inhabiting the area.
Q. 5. List abiotic components of the environment.
Ans.—  Air, water, soil, light and temperature.
Q. 6. List a few human activities that affect the habitat adversely.
Ans.—Deforestation, mining, quarry, brick kiln, urbanisation, jhoom cultivation, wars, automobiles, dams etc.
Q. 7. What is interdependence ?
Ans.— Within any community, some species, although a part of the community, are dependant upon one another for their survival. This phenomenon is called interdependence.
Q. 8. How is balance maintained in the environment ?
Ans.— 1. The balance in environment is due to interdependence among various components.
2. It is also due to perfect systematic cycling of various chemicals such as, water, oxygen, carbon and nitrogen.
Q. 9. Name the process for which plants need light, water and air (CO₂).
Ans.— Photosynthesis.
Q. 10. What is soil ?
Ans.— Soil is uppermost crust of earth and major physical component of the environment.
Q. 11. What is the importance of soil ?
Ans.— Soil supports terrestrial plants and animals and it decides the diversity of life in an area.
Q. 12. How is soil formed ?
Ans.— Soil is formed by weathering of rocks.
Q. 13. Name the gaseous components of biosphere.
Ans.— CO₂, O₂ and Nitrogen.
Q. 14. Name the source of energy for the process of photosynthesis.
Ans.— Sun energy.
Q. 15. Define pollution.
Ans.— Pollution is an undesirable change in physical, chemical or biological characteristics of air, water or land caused by pollutants.
Q. 16. What are pollutants ?
Ans.— The substances causing pollution are termed pollutants.
Q. 17. What are the three major types of pollution ?
Ans.— Water, air and soil pollution.
Q. 18. What is soil pollution ?
Ans.— Soil pollution removal of useful components from soil and addition of other substances which adversely affect the soil, termed soil pollution.
Q.19. Which part of solar radiation is absorbed by ozone layer ?
Ans.— UV rays.
Select the Correct Answer :
1. In air pollution, industries are :
(A) Line sources
(B) Point sources
(C) Area sources
(D) None of above.
Ans.— (B) Point sources
2. Nitrogen oxides and hydrocarbons released by automobiles interact to form :
(A) Carbon monoxide
(B) Sulphur dioxide
(C) PAN and ozone
(D) Aerosols.
Ans.—(C) PAN and ozone
3. Aerosols are released by :
(A) Industries
(B) Aeroplanes
(C) Automobiles
(D) Fertilizers
Ans.— (B) Aeroplanes
4. Chlorosis in plants is caused by :
(A) CO pollution
(B) NO2  pollution
(C) SO2  pollution
(D) Soot particles.
Ans.— (C) SO2  pollution
5. Living organisms and water, air and earth where they live together form :
(A) Hydrosphere
(B) Atmosphere
(C) Lithosphere
(D) Biosphere
Ans.—(D) Biosphere
6. Green House effect is due to :
(A) CFC’s
(B) O3
(C) Gases that check reflected infra-red radiation pass through them
(D) All the above.
Ans.— (D) All the above.
7. Concentration of nitrogen remains constant by :
(A) Nitrogen cycle
(B) Thundering and lightning
(C) Enzymes
(D) Both (A) and (B).
Ans.— (D) Both (A) and (B).
8. More than 70% of world’s fresh water is contained in : 
(A) polar ice
(B) glaciers
(C) Antarctica
(D) Greenland.
Ans.— (A) polar ice
9. Oxygen is abundant element on earth. It is found in elemental form upto 21%. It occurs as :
(A) Earth’s crust
(B) CO2
(C) In gaseous state
(D) All of the above.
Ans.— (D) All of the above.
10. One of the useful activities of most of the bacteria is :
(A) nitrogen fixation
(B) nitrification
(C) operation of biogeochemical cycles
(D) All of the above
Ans.— (B) nitrification
11. The main role of bacteria in the carbon cycle involves :
(A) assimilation of nitrogenous compounds
(B) photosynthesis
(C) chemosynthesis
(D) digestion or breakdown of organic compounds.
Ans.— (D) digestion or breakdown of organic compounds.
12. Ozone depletion is occurring due to :
(A) CFC’s
(B) CO
(D) None of above.
Ans.— (A) CFC’s
13. Ozone hole is :
(A) absence of O3 in troposphere
(B) absence of O3 in stratosphere
(C) deficiency of O3 in stratosphere
(D) deficiency of O3 in troposphere.
Ans.— (B) absence of O3 in stratosphere
14. Maximum contribution of O₂ is from :
(A) Phytoplankton
(B) Grasslands
(C) herbs and shrubs
(D) dense forest.
Ans.— (A) Phytoplankton
15. Cycling of elements of any ecosystem is called : 
(A) chemical cycle
(B) geochemical cycle
(C) biogeochemical cycle
(D) geological
Ans.— (C) biogeochemical cycle
16. One way cycle is :
(A) CO2 cycle
(B) H2 O cycle
(C) free energy cycle
(D) O2 cycle.
Ans.— (C) free energy cycle
17. Soil fertility is reduced by :
(A) Crop-rotation
(B) Nitrogen fixing bacteria
(C) decaying organic matter
(D) Intensive agriculture.
Ans.— (D) Intensive agriculture.
18. Of the total water evaporated from oceans, precipitation returns :
(A) 100%
(B) 90%
(C) 75%
(D) 50%.
Ans.— (B) 90%
19. Greatest problem in water conservation is to reduce the amount of :
(A) ground water
(B) precipitation
(C) runoff water
(D) evaporation.
Ans.— (C) runoff water

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