NCERT Exemplar Chapter 14 Natural Resources Class 9 Science Solutions

NCERT Exemplar Class 9 Science Chapter 14 Natural Resources Solutions

NCERT Exemplar Solutions for Class 9 Science Chapter 14 Natural Resources covers all the important questions and answers as well as advanced level questions. It helps in learning about the natural resources, soil erosion, greenhouse gasses, acid rain, water pollution, rainwater harvesting, greenhouse effect, atmosphere, conservation of rain, acid rain and smog.

The NCERT Exemplar solutions for class 9 science is very important in the examination. NCERT Exemplar Solutions for Class 9 Science Chapter 14 Natural Resources is provided by our experts. They prepared the best solutions which help the students in understanding the solutions in an easy way. This chapters also covers the other topics like Soil Erosion, wrong agricultural practices, immediate condensation, rainfall pattern, pollution of water and soil, deforestation, afforestation and conservation of natural resources.

Chapter Name	Chapter 14 Natural Resources
Book Title	NCERT Exemplar for Class 9 Science
Related Study	NCERT Solutions for Class 9 Science Chapter 14 Natural Resources Revision Notes for Class 9 Science Chapter 14 Natural Resources MCQ for Class 9 Science Chapter 14 Natural Resources Important Questions for Class 9 Science Chapter 14 Natural Resources
Topics Covered	MCQ Short Answers Questions Long Answers Questions

NCERT Exemplar Solutions for Chapter 14 Natural Resources Class 9 Science

Multiple Choice Questions

1. The atmosphere of the Earth is heated by radiations which are mainly :

(a) Radiated by the Sun
(b) Re-radiated by land
(c) Re-radiated by water
(d) Re-radiated by land and water

Solution

(d) Re-radiated by land and water

Heat from the sun reaches the earth and water. This heat is re-radiated by earth and water that heats the atmosphere.

2. If there were no atmosphere around the Earth, the temperature of the Earth will :
(a) Increase
(b) Go on decreasing
(c) Increase during day and decrease during night
(d) Be unaffected

Solution

(c) Increase during day and decrease during night

Atmosphere prevents a lot of heat from the sun to reach the earth’s surface. During the night, the atmosphere also prevents the escape of heat from the earth. Thus atmosphere is responsible for maintaining an ambient temperature on earth.

3. What would happen, if all the oxygen present in the environment is converted to ozone?
(a) We will be protected more
(b) It will become poisonous and kill living forms
(c) Ozone is not stable, hence it will be toxic
(d) It will help harmful Sun radiations to reach Earth and damage many life forms.

Solution

(b) It will become poisonous and kill living forms

All the organisms living on earth require oxygen to live. All the living beings will die if oxygen is converted to ozone.

4. One of the following factors does not lead to soil formation in nature :
(a) The Sun
(b) Water
(c) Wind
(d) Polythene bags

Solution

(d) Polythene bags

5. The two forms of oxygen found in the atmosphere are :
(a) Water and ozone
(b) Water and oxygen
(c) Ozone and oxygen
(d) Water and carbon dioxide

Solution

(c) Ozone and oxygen

6. The process of nitrogen-fixation by bacteria does not take place in the presence of :
(a) Molecular form of hydrogen
(b) Elemental form of oxygen
(c) Water
(d) Elemental form of nitrogen

Solution

(b) Elemental form of oxygen

7. Rainfall patterns depend on :
(a) the underground water table
(b) the number of water bodies in an area
(c) the density pattern of human population in an area
(d) the prevailing season in an area

Solution

(b) the number of water bodies in an area

Water bodies provide water for evaporation which is converted into clouds. Clouds in turn bring rainfall. Lack of water bodies will reduce the humidity which will affect the rainfall pattern.

8. Among the given options, which one is not correct for the use of large amount of fertilizers and pesticides?
(a) They are eco-friendly
(b) They turn the fields barren after some time
(c) They adversely affect the useful component from the soil
(d) They destroy the soil fertility

Solution

(a) They are eco-friendly

9. The nitrogen molecules present in air can be converted into nitrates and nitrites by :
(a) A biological process of nitrogen fixing bacteria present in soil
(b) A biological process of carbon fixing factor present in soil
(c) Any of the industries manufacturing nitrogenous compounds
(d) The plants used as cereal crops in field

Solution

(a) A biological process of nitrogen fixing bacteria present in soil

Cereals cannot fix the nitrogen on their own. They comprise bacteria in their root nodules which will convert nitrates to nitrites. This process is called nitrogen fixation.

10. One of the following processes is not a step involved in the water-cycle operating in nature :
(a) Evaporation
(b) Transpiration
(c) Precipitation
(d) Photosynthesis

Solution

(d) Photosynthesis

Photosynthesis is a part of carbon cycle.

11. The term “water-pollution” can be defined in several ways. Which of the following statements does not give the correct definition?

(a) The addition of undesirable substances to water- bodies
(b) The removal of desirable substances from water- bodies
(c) A change in pressure of the water bodies
(d) A change in temperature of the water bodies

Solution

(c) A change in pressure of the water bodies

Physical causes lead to change in pressure on water bodies.

12. Which of the following is not a greenhouse gas?
(a) Methane
(b) Carbon dioxide
(c) Carbon monoxide
(d) Ammonia

Solution

(d) Ammonia

13. Which step is not involved in the carbon cycle?
(a) Photosynthesis
(b) Transpiration
(c) Respiration
(d) Burning of fossil fuels

Solution

(b) Transpiration

Transpiration is the process of exhaling of water by the trees. Transpiration is a part of water cycle.

14. ‘Ozone-hole’ means :
(a) A large sized hole in the ozone layer
(b) Thinning of the ozone layer
(c) Small holes scattered in the ozone layer
(d) Thickening of ozone in the ozone layer

Solution

(b) Thinning of the ozone layer

15. Ozone-layer is getting depleted because of :
(a) excessive use of automobiles
(b) excessive formation of industrial units
(c) excessive use of man-made compounds containing both fluorine and chlorine
(d) excessive deforestation.

Solution

(c) excessive use of man-made compounds containing both fluorine and chlorine

Carbon and fluorine react with ozone and convert it into oxygen. This results in thinning of ozone layer which is called ozone depletion.

16 Which of the following is a recently originated problem of environment?
(a) Ozone layer depletion
(b) Greenhouse effect
(c) Global warming
(d) All of these

Solution

(d) All of these

17. When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of this nitrogen?
(a) It moves along with oxygen into the cells
(b) It comes out with the CO₂ during exhalation
(c) It is absorbed only by the nasal cells
(d) Nitrogen concentration is already more in the cells so it is not at all absorbed.

Solution

(b) It comes out with the CO₂ during exhalation

Nitrogen is the most abundant gas in nature and hence during inhalation nitrogen also goes inside our body along with oxygen. But it is not utilized by our body and is exhaled along with carbon dioxide.

18. Top-soil contains the following :
(a) Humus and living organisms only
(b) Humus and soil particles only
(c) Humus, living organisms and plants
(d) Humus, living organisms and soil particles.

Solution

(d) Humus, living organisms and soil particles.

19. Choose the correct sequences :
(a) CO₂ in atmosphere → decomposers → organic carbon in animals → organic carbon in plants
(b) CO₂ in atmosphere → organic carbon in plants → organic carbon in animals → inorganic carbon in soil
(c) Inorganic carbonates in water → organic carbon in plants → organic carbon in animals → scavengers
(d) Organic carbon in animals → decomposers → CO₂ in atmosphere → organic carbon in plants

Solution

(b) CO₂ in atmosphere → organic carbon in plants → organic carbon in animals → inorganic carbon in soil

During photosynthesis green plants utilize atmospheric carbon-dioxide to make organic compounds. When animals eat plants, organic compounds reach the animals. When plant or animals die they get decomposed to turn into inorganic carbon.

20. Major source of mineral in soil is the :
(a) Parent rock from which soil is formed
(b) Plants
(c) Animals
(d) Bacteria

Solution

(a) Parent rock from which soil is formed

Rock weathering is a process which forms the soil. Rocks are naturally occurring soil aggregates which are rich in minerals.

21. Total Earth’s surface covered by water is :
(a) 75%
(b) 60%
(c) 85%
(d) 50%

Solution

(a) 75%

22. Biotic component of biosphere is not constituted by :
(a) producers
(b) consumers
(c) decomposer
(d) air

Solution

(d) air

Biotic component of biosphere comprises of the living entities, air is a non-living component.

23. An increase in carbon dioxide content in the atmosphere would not cause :
(a) More heat to be retained by the environment
(b) Increase in photosynthesis in plants
(c) Global warming
(d) Abundance of desert plants

Solution

(d) Abundance of desert plants

Plants require oxygen, minerals and water to grow and develop.

24. Oxygen is returned to the atmosphere mainly by :
(a) Burning of fossil fuel
(b) Respiration
(c) Photosynthesis
(d) Fungi

Solution

(c) Photosynthesis

Plants take CO₂ from environment and they return back oxygen by a process called photosynthesis.

25. Low visibility during cold weather is due to :
(a) Formation of fossil fuel
(b) Unburnt carbon particles or hydrocarbons suspended in air
(c) Lack of adequate power supply
(d) None of the above

Solution

(b) Unburnt carbon particles or hydrocarbons suspended in air

Unburnt carbon particles and hydrocarbons suspend in air to create smog. The visibility is low in cold weather due to smog.

26. Growth of lichens on barren rocks is followed by the growth of :
(a) moss
(b) ferns
(c) gymnosperms
(d) algae

Solution

(a) moss

Lichens release certain enzymes which makes the rock suitable for the growth of moss. Moss in turn leads to the formation of soil which allows growth of more plants.

27. Marked temperature changes in aquatic environment can affect :
(a) Breeding of animals
(b) More growth of aquatic plants
(c) Process of digestion in animals
(d) Availability of nutrients

Solution

(a) Breeding of animals

Most aquatic animals are cold-blooded. Their egg and larvae are highly susceptible to temperature changes.

28. Soil erosion can be prevented by :
(a) Raising forests
(b) Deforestation
(c) Excessive use of fertilizer
(d) Overgrazing by animals

Solution

(a) Raising forests

The roots of the trees in the forest hold on the soil thus by planting more trees, soil can be prevented from being eroded.

29. What happens when rain falls on soil without vegetation cover?
(a) Rain water percolates in soil efficiently
(b) Rain water causes loss of surface soil
(c) Rain water leads to fertility of the soil
(d) Rain water does not cause any change in soil

Solution

(b) Rain water causes loss of surface soil

Roots hold the topsoil and prevent them from getting washed away during the rainfall. When there is no vegetation, the surface soil gets washed away.

30. Oxygen is harmful for :
(a) ferns
(b) nitrogen fixing bacteria
(c) chara
(d) mango tree

Solution

(b) nitrogen fixing bacteria

Nitrogen-fixing bacteria have anaerobic respiration and they get killed when exposed to oxygen.

Short Answer Questions

31. Rivers from land, add minerals to sea water. Discuss, how?

Solution

Water is a universal solvent that can dissolve a large number of substances. When water flows through rocks which have certain soluble minerals, some of them get dissolved in the water in this process. Thus, rivers carry many nutrients from the land to the sea. The salts continue to remain in the sea as no water flows out of the sea.

32. How can we prevent the loss of topsoil?

Solution

Methods of Reducing Soil Erosion :

1. Afforestation: Plants and trees protect soil erosion by binding soil by roots.
2. Proper irrigation system: Root systems stabilizes the soil and prevents soil erosion.
3. Crop rotation: It maintains the fertility water holding capacity of the soil. Thus, it prevents soil erosion.
4. Contour farming: It prevents soil erosion by reducing sediment and run off and increasing water infiltration.
5. By preventing excessive grazing by animals.
6. Prevent deforestation.

33. How is the life of organisms living in water affected when water gets polluted?

Solution

Life of organisms living in water affected in following ways when water gets polluted:

1. Addition of pollutants like fertilizers and chemicals to the water bodies will cause diseases in aquatic organisms.
2. Pollutants increase the biological oxygen demand of organisms living in water, since, the dissolved oxygen in the water reduces drastically.
3. The nutrients in fertilizers cause rapid growth of algae, also known as an algal bloom. This process is known as eutrophication. Algal blooms cover the surface of the water so sunlight does not penetrate as far down as it typically would, reducing the ability of underwater plants to perform photosynthesis and produce oxygen.
4. Pollution can affect the temperature of water bodies, while aquatic animals can manage a little change in temperature only. Heated water decreases the oxygen content of water thereby leading to the death of aquatic organisms. Similarly, cold water affects eggs and larvae and some invertebrates of the aquatic ecosystem.
5. The increase in concentration of harmful, non-biodegradable chemical substances in the body of living organisms throughout the trophic levels of a food chain is called biological magnification.

34. During summer, if you go near the lake, you feel relief from the heat, why?

Solution

Due to high temperature in summer, land and water in the lake gets heated. Since land gets heated faster than water, the air over land would also be heated faster than the air over water bodies. Heated air being light starts rising up, thus region of low pressure is created over the land. As a result, the air from the top of the water bodies rushes into this area because air moves from high pressure area towards low pressure area. This wind contains moisture and thus makes us cool and gives us relief.

35. In coastal area, wind current moves from the sea towards the land during day; but during night it moves from land to the sea. Discuss the reason.

Solution

Air above the land gets heated quickly during day and starts rising. This creates a region of low pressure as a result air over sea rushes into this area of low pressure. This movement of air from one region to the other creates winds. During night water cools down slowly, the air above water is warmer than the air on land. So, air moves from land to sea creating winds.

36. Following are a few organisms
(a) lichens
(b) mosses
(c) mango tree
(d) cactus.
Which among the above can grow on stones; and also help in formation of soil? Write the mode of their action for making soil.

Solution

• Lichen and mosses can grow on stones and they also help in formation of soil.
• Lichens grow on rocks and release certain enzymes which favour the growth of mosses.
• Mosses form clumps of soil from the rock which results in the formation of topsoil.

37. Soil formation is done by both abiotic and biotic factors. List the names of these factors by classifying them as abiotic and biotic.

Solution

1. Abiotic factors making soil: Sun, water and wind
2. Biotic factors: lichens, mosses and trees

38. All the living organisms are basically made up of C, N, S, P, H and O. How do they enter the living forms? Discuss.

Solution

The living organisms are basically made up of C, N, S, P, H₂ and O₂. Most of these elements enter in living forms through plants. Plants take up H₂ and C by the process of photosynthesis and the other minerals absorb from the soil. They convert them into food. Consumers take in O₂ and H₂ during respiration and the rest of the minerals are taken through the food. The food prepared by plants is consumed by herbivores and then passes through different levels of food chains for utilization by consumers. At last, the decomposers decompose the dead bodies and the wastes given out by various consumers, thus inorganic nutrient return to the environment. Decomposition or biodegradation results in the breakdown of complex organic materials to forms of carbon that can be used by other organisms. Through the metabolic processes of fermentation and respiration, organic molecules are eventually broken down to CO₂ which is returned to the atmosphere. Some bacteria remove N₂ from the atmosphere and converts it to ammonia (NH₃) by nitrogen fixation process and by symbiotic associations in plants. Other nitrogen-fixing bacteria are free-living in soil and aquatic habitats. Soil also plays important role in biogeochemical cycle which is a main source of recycling of nutrients from atmosphere to soil and then to water.

39. Why does the percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere?

Solution

Oxygen, nitrogen and carbon dioxide are used by humans for their growth and development. But these gases are returned to the environment in one or other form. This process of using natural resources and giving them back to nature is called biogeochemical cycle. Because of this cycle the percentage of gases remain almost the same in the atmosphere.

40. Why does Moon have very cold and very hot temperature variations, e.g., from –190°C to 110°C even though it is at the same distance from the Sun as the Earth is?

Solution

The atmosphere of the earth prevents the overheating of the earth during day time. On the other hand, Moon does not have atmosphere. Therefore, it appears to be hotter during day time. Lack of atmosphere in moon also allows heat to escape during the night. This is the reason why the temperature varies on moon surface.

41. Why do people love to fly kites near the seashore?

Solution

The air above land gets heated faster and being light and starts rising up which creates a region of low pressure is created. So, the air from the surrounding areas and from the top of the water bodies moves towards land and fills the low pressure area. This blowing of breeze during day time near the sea shore helps in the flying of kites. Therefore, people love to fly kites near the seashore.

42. Why does Mathura refinery pose problems to the Taj Mahal?

Solution

Mathura refinery releases oxides of sulphur which in turn causes acid rain. Acid rain corrodes the marble of Taj Mahal. Suspended particulate matter (dust and exhaust) are causing the discoloration of the Taj Mahal. This is the reason why Mathura refinery poses a problem to the Taj Mahal.

43. Why do not lichens occur in Delhi whereas they commonly grow in Manali or Darjeeling?

Solution

Delhi occurs in semi-arid area where atmospheric moisture is low. Lichens are sensitive to sulphur dioxide (SO₂) and bio-indicators of air pollution. Sulphur dioxide occurs in sufficient quantity in the atmosphere of Delhi due to the pollution caused by large number of vehicles, factories, etc. In Manali and Darjeeling, the atmosphere is humid and sulphur dioxide pollution is comparatively low making it more conducive to lichen growth.

44. Why does water need conservation even though large oceans surround the land masses?

Solution

Water covers nearly 75% of the Earth but most of the water present in the form of sea and ocean. Seawater is not suitable for the livelihood of humans and plants. Freshwater resources are limited and thus they must be conserved. Only three percent of all the water is fresh water, and one percent is available for drinking water. Moreover, most of the sources of water supply are contaminated by industrial waste or sewage. Therefore, it is necessary to conserve water.

45. There is mass mortality of fishes in a pond. What may be the reasons?

Solution

The following can the reasons for the mass mortality of fishes in a pond :

1. Addition of mercuric compounds and other toxic chemicals.
2. Blockage of gills by pollutants.
3. Fertilizer pollution does not make fish grow bigger.
4. Heated water flowing out of the thermal power plants increase the temperature of the water body. It may also affect the mortality rate of fishes.
5. Addition of poisonous compounds in water.
6. It mainly contains organic matter, which is biodegradable. Microorganisms involved in their degradation consume a lot of oxygen and the content of oxygen in the water body decreases leading to the death of fishes.

46. Lichens are called pioneer colonisers of bare rock. How can they help in formation of soil?

Solution

Lichens release enzymes which break the rock into smaller pieces. In this way the lichens help in formation of soil.

47. (i) “Soil is formed by water.” If you agree to this statement then give reasons.
(ii) Water helps in the formation of soil in two ways.

Solution

(i) Water causes soil formation through the following steps:

• Water causes wear off of the rocks for a long period of time.
• Water makes rubbing between the rocks to smaller particles which are deposited as soil.
• On freezing, water expands to cause breaks in the rock.

(ii) Fast flowing water often carries big and small particles of rock with it. These rocks rub against other and wear down into smaller and smaller particles. So, soil is found in places far away from its parent-rock.

48. Fertile soil has lots of humus. Why?

Solution

The fertile soil has lots of microorganisms which decompose dead and organic matter and convert then to humus. Humus provides nutrients, absorbs water and makes the soil porous. Earthworms feed on the humus and increase its fertility. Humus causes the soil to become more porous and allows water and air to penetrate deep underground and also gives minerals.

49. Why step farming is common in hills?

Solution

Step farming is used in hills to prevent soil erosion through water currents on the slopes. It is also known as terracing. The mountain is made into steps which slow down the speed of rainwater which prevent damage to crops. Moreover, it allows farmers to cultivate crops on steep slope, and thus provides more usable land.

50. Why are root nodules useful for the plants ?

Solution

Root nodules are the home for nitrogen-fixing bacteria called a Rhizobium. Rhizobium increases soil fertility by fixing atmospheric nitrogen.

Long Answer Questions

51. How do fossil fuels cause air pollution?

Solution

Fossil fuels like petrol, diesel and kerosene release oxide of sulphur, nitrogen and carbon. Sulphur and nitrogen oxides cause acid rain. Burning fossil fuels releases carbon monoxide which in turn increases the carbon dioxide in the atmosphere. This affects the living organisms. The amount of suspended particles in the air also increases due to burning of fossil fuels. This reduces the visibility.

52. What are the causes of water pollution? Discuss how you can contribute in reducing water pollution.

Solution

Causes of water pollution are as follows:

• Chemical fertilizers and pesticides consist of poisonous chemical which reach the water body and make it toxic.
• Dumping of sewage directly into water bodies.
• Release of industrial effluents into water bodies.

The steps to betaken in order to reduce water pollution are:

• Stop connecting sewage lines directly to water bodies.
• Avoid throwing garbage and other domestic waste into water resource.
• Prevent dumping of toxic chemical into water body.
• Avoid washing of clothes near water bodies.

53. A motorcar, with its glass totally closed, is parked directly under the Sun. The inside temperature of the car becomes very high. Explain, why?

Solution

If a closed car is parked directly under the Sun then the inside temperature of the car becomes very high because of greenhouse effect. Infrared radiations emitted by the sun pass through the transparent glass and increases the temperature inside the car. These radiations have smaller wavelength than the radiations emitted by the car. So, the transparent glass remains opaque to the radiations emitted by the car which further increases the temperature.

54. Justify “Dust is a pollutant”.

Solution

Dust is a fine powder of tiny earth particles and waste matter. The dust is carried to the atmosphere by wind. Dust causes allergy in humans and affects the plant growth by blocking the stomata on the leaves. Dust also carries toxic substance from the environment to pollute the water bodies affecting the aquatic life. Therefore, we can say that dust is a pollutant.

55. Explain the role of the Sun in the formation of soil.

Solution

During the afternoon, the Sun heats the rock. which results in the expansion of rocks. During the night, contraction takes place when the rocks cool down. But the rate of contraction is not the same as the rate of expansion. Because of this difference the rocks get cracked and form small rock particles.

56. Carbon dioxide is necessary for plants. Why do we consider it as a pollutant?

Solution

Carbon dioxide is a green-house gas which causes global warming this is the reason why carbon dioxide is considered as a pollutant. This results in change of earth’s climate. Excess of CO₂ is also harmful for the plants. Increased CO₂ levels changes physiology, growth and chemistry of plants. Increased concentration ofCO₂ also causes suffocation, hard breathing and choking issues.