NCERT Exemplar for Class 9 Science Chapter 14 - Natural Resources (Book Solutions)

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

Ans: (d) re-radiated by land and water

Explanation: The sun's heat reaches the earth and warms the soil and water. The heat from the land and water is then re-radiated into the atmosphere, warming it.

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

Ans: (c) increase during day and decrease during night

Explanation: This is because the atmosphere saves the earth from becoming too hot during day time & also prevents the heat from escaping during the night. Thus, an ideal temperature is maintained on the earth throughout the period of 24 hour.

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.

Ans: (b) It will become poisonous and kill living forms

Explanation: Living beings need oxygen for respiration. Lack of oxygen will kill all living beings. 

4. One of the following factors does not lead to soil formation in nature

(a) the sun

(b) water

(c) wind 

(d) polythene bags

Ans: (d) polythene bags

Explanation: Polythene bags contaminate the soil and cause it to become barren.

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

Ans: (c) ozone and oxygen

Explanation: Ozone is an allotrope of 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

Ans: (b) elemental form of oxygen

Explanation: Nitrogen-fixation is a process in which the atmospheric nitrogen N2 is converted to ammonium NH4+ , nitrates NO3-or nitrites NO2- . Nitrogen fixation can occur naturally or artificially. Nitrogen fixing bacteria carry out this activity in the natural manner of nitrogen fixation. Although atmospheric nitrogen , or N2 , is largely inert, nitrogen-fixing bacteria include the nitrogen-fixing enzyme nitrogenase, which is involved in nitrogen fixation. However, the nitrogenase enzyme is sensitive to being destroyed by the elemental form of oxygen. As a result, nitrogen-fixing bacteria thrive in anaerobic environments such as root nodules.

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

Ans: (b) the number of water bodies in an area 

Explanation: Water bodies provide water for evaporation. Water vapours condense after evaporation to generate rainfall. A lack of water bodies in an area reduces humidity in the air, which has a negative impact on rainfall.

8. Among the given options, which one is not correct for the use of large amount of fertilisers 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

Ans:  (a) They are eco-friendly

Explanation: Adverse effects mentioned in other options make the fertilizers and pesticides detrimental to the ecosystem.

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

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

Explanation: Cereal crops cannot fix nitrogen on their own. Their root nodules are home to nitrogen-fixing microorganisms. As a result, option (d) is erroneous. Factories cannot use nitrogen from the air to produce nitrogenous compounds; instead, they employ petrochemicals. As a result, option (c) is erroneous. Option (b) refers to carbon fixing and is hence inaccurate.

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

Ans: (d) photosynthesis

Explanation: Photosynthesis is involved in the carbon cycle not in the water 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

Ans: (c) A change in pressure of the water bodies 

Explanation: A change in the pressure of water bodies can occur due to physical causes and does not result in water contamination.

12. Which of the following is not a greenhouse gas? 

(a) Methane 

(b) Carbon dioxide 

(c) Carbon monoxide 

(d) Ammonia

Ans: (d) Ammonia

Explanation: The gases that come under the category of greenhouse gases  include methane, carbon dioxide, and nitrous oxide etc. They add to the greenhouse effect. The greenhouse effect is unaffected by ammonia. As a result, option D ammonia will be the correct response.

13. Which step is not involved in the carbon-cycle? 

(a) Photosynthesis 

(b) Transpiration 

(c) Respiration 

(d) Burning of fossil fuels 

Ans: (b) Transpiration

Explanation: Transpiration is the loss of water vapor from the aerial parts of the plants.It contributes to the water cycle but not to the carbon 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

Ans: (b) thinning of the ozone layer 

Explanation: The phrase 'hole' eliminates alternatives 'a' and 'c'. Option 'd' is ruled out since thickening is synonymous with strengthening.

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

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

Explanation: Chlorofluorocarbons are compounds that contain both fluorine and chlorine (CFCs). Chlorine and fluorine react with ozone to convert it to oxygen, resulting in ozone layer depletion.

16. Which of the following is a recently originated problem of the environment? 

(a) Ozone layer depletion 

(b) Greenhouse effect 

(c) Global warming 

(d) All of the above

Ans: (d) All of the above

Explanation: All the problems mentioned here have originated after the industrial revolution. 

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.

Ans: (b) It comes out with the CO2 during exhalation

Explanation: Because nitrogen is the most abundant gas in the air, it enters our bodies through inhalation. But nitrogen is not utilized by the body hence,comes out during exhalation.

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.

Ans: (d) Humus, living organisms and soil particles.

Explanation: Top soil is the soil's top and outermost layer, which is typically 2 to 8 inches thick. It is often black in colour because of humus, which is partially decaying organic matter, soil particles, and live creatures such as soil bacteria, among other things.

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

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

Explanation: Green plants use carbon dioxide from the atmosphere during photosynthesis. Thus, organic compounds are made by plants. When an animal consumes food, organic molecules from plants enter the animal's body (directly or indirectly). When an animal or plant dies, the breakdown of the dead remains that results in the creation of inorganic carbon in the soil.

20. Major source of mineral in soil is the

(a) parent rock from which soil is formed 

(b) plants 

(c) animals 

(d) bacteria

Ans: (a) parent rock from which soil is formed 

Explanation: Soil is generated via a process known as "weathering of rocks," which involves the breakdown of rocks and the formation of soil. As a result, the minerals found in the rocks would likewise be found in the soil created from them. Other factors, such as bacteria, plants, and bacteria, aid in soil formation by breaking down rocks.

21. Total earth’s surface covered by water is 

(a) 75% 

(b) 60% 

(c) 85%

(d) 50%

Ans: (a) 75%

22. Biotic component of biosphere is not constituted by 

(a) producers 

(b) consumers 

(c) decomposer 

(d) air

Ans: (d) air

Explanation: Living beings make up biotic components. Because air is a non-living substance, it cannot be included in biotic components.

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

Ans: (d) abundance of desert plants

Explanation: Desert does not have the suitable condition for the abundant growth of plants. Apart from carbon dioxide plants also need oxygen, water and minerals for proper growth and development. But water is a scarce resource in deserts. 

24. Oxygen is returned to the atmosphere mainly by 

(a) burning of fossil fuel 

(b) respiration 

(c) photosynthesis

(d) fungi

Ans: (c) photosynthesis

Explanation: Agents in other options return carbon dioxide to the atmosphere.

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 these

Ans: (b) unburnt carbon particles or hydrocarbons suspended in air

Explanation: Unburnt carbon particles and hydrocarbons suspended in the air create smog that results in low visibility.

26. Growth of Lichens on barren rocks is followed by the growth of 

(a) moss 

(b) ferns 

(c) gymnosperms 

(d) alga

Ans: (a) moss

Explanation: Lichens secrete enzymes that break down rocks and make them ideal for mass growth. Mosses aid in the production of soil and the growth of higher 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.

Ans: (a) breeding of animals 

Explanation: Temperature changes may hamper the growth of aquatic plants in negative terms.  Availability of nutrients in water does not depend on temperature but on availability of minerals in the substratum. Temperature fluctuations in water affect digestion in aquatic animals but it will have no effect on digestion in land animals. Thus, other options can be ruled out.

28. Soil erosion can be prevented by 

(a) raising forests 

(b) deforestation 

(c) excessive use of fertilizer 

(d) overgrazing by animals

Ans: (a) raising forests 

Explanation: Agents in other options will increase the phenomenon of soil erosion hence , remaining options are incorrect.

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

Ans: (b) Rain water causes loss of surface soil

Explanation: Plants hold top soil with their roots and thus prevent topsoil from getting washed away by the rain. 

30. Oxygen is harmful for

(a) ferns 

(b) nitrogen fixing bacteria 

(c) chara 

(d) mango tree

Ans: (b) nitrogen fixing bacteria 

Explanation: Oxygen deactivates the enzymes responsible for nitrogen fixation, such as nitrogenase reductase, and hence impedes the nitrogen fixation process. Some nitrogen fixers function in anaerobic conditions to reduce oxygen levels or allow oxygen to mix with leghemoglobin.

SHORT ANSWER QUESTIONS

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

Ans: Being a universal solvent water has the ability to dissolve a wide variety of substances. Some soluble minerals dissolve in water as water flows through soluble mineral-containing rocks. As a result, rivers convey a considerable amount of nutrients from the land to the sea.

32. How can we prevent the loss of topsoil?

Ans: Loss of topsoil can be avoided by-: 

(i) increasing vegetation cover.

(ii) reducing tree fall.

(iii) preventing animal overgrazing.

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

Ans: The addition of undesired chemicals such as pesticides, fertilizers, industrial and domestic wastes not only kills the organisms but also causes diseases in the aquatic organisms. There is a decrease in the amount of dissolved oxygen in water, which has a negative impact on aquatic life.

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

Ans: The water from the surface of a lake keeps on evaporating. This creates a cooling effect in the surroundings. Due to this, when we go near a lake we feel relief from the heat.

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

Ans: Winds are created by the movement of air from one location to another.During the day, the air above the land heats up quickly and begins to rise. This results in the formation of a low-pressure area, into which air from the sea rushes. During the night, when water slowly cools, the air above water is warmer than the air on land. As a result, air travels from land to sea, resulting in winds.

36. Following are a few organisms 

(a) lichen (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.

Ans: Lichens and mosses i.e. (a) as well as (b). Lichens and mosses produce chemicals that break down the stones, resulting in soil formation.

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

Ans: Abiotic factors making soil— sun, water and wind.

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. 

Ans: The basic components of many biomolecules are C, N, S, P, H, and O. Living creatures are composed of countless biomolecules, the majority of which enter the living world via plants. Photosynthesis is the source of carbon. Nitrogen-fixing bacteria fix nitrogen in soil so that plants can absorb nitrogenous substances. Sulphur and phosphorus exist in soil as minerals and are absorbed by plants together with water. When plants take water, they absorb hydrogen and oxygen. When animals drink water, they absorb hydrogen and oxygen as well. Living beings absorb oxygen by inhaling as well. Finally, these elements are absorbed by animals when they consume plants, either directly or indirectly.

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

Ans: The percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere because these elements are constantly used by living things. However, these elements go through a cyclical process that assures they are returned to the atmosphere via diverse processes. The biogeochemical cycle refers to the cyclic process of consuming various elements and returning them to the atmosphere. 

40. Why does the 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?

Ans: There is no atmosphere on the moon. As a result, unlike on Earth, there is no mechanism to keep the surface from warming throughout the day. Furthermore, the lack of atmosphere allows all of the heat to escape during the night. Hence , the temperature on the moon varies greatly as a result of these factors.

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

Ans: During the day, sea breezes blow in coastal locations. The speed of the sea breeze is great for kite flying. As a result, people enjoy flying kites near the coast.

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

Ans: The Mathura refinery emits harmful gases (such as oxides of sulphur), which induce acid rain that result, erosion of the Taj Mahal's marbles.

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

Ans: This is because it is a bioindicator that is sensitive to SO2 pollution caused by cars. Delhi has the most autos, resulting in a very filthy atmosphere.

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

Ans: Marine water is not directly beneficial to human or plant life. To meet the demands, the uneven distribution of limited freshwater resources necessitates conservation.

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

Ans: The possible reasons can be-:

 (i) thermal pollution.

(ii) addition of harmful compounds such as mercury to water.

(iii) obstruction of fish gills by any water pollutant.

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

Ans: Lichens produce chemical compounds that break down rocks into smaller bits, resulting in the formation of soil.

47. “Soil is formed by water.” If you agree to this statement then give reasons.

Ans: Water aids in soil development in the following ways:

(i) Over time, water causes the 'wear off' of rocks.

(ii) It also causes the rocks to rub against one another, resulting in minute particles that are carried downstream and deposited as soil.

(iii) When water freezes in rock cracks, it expands and breaks the rock into smaller pieces.

48. Fertile soil has lots of humus. Why?

Ans: Fertile soils are rich in organisms that digest dead organic matter, resulting in the formation of humus. Humus adds minerals to the soil, absorbs water, and makes it porous.

49. Why is step farming common in hills?

Ans: Slopes on farms in the hills are steep. Because of the high slope, top soil is always at risk of being washed away by rainwater. Efforts are being undertaken to avoid soil erosion. As a result, step farming is frequent in hills.

50. Why are root nodules useful for the plants?

Ans: Nitrogen-fixing  bacteria i.e. Rhizobium  are found in root nodules, where they fix atmospheric nitrogen and increase soil fertility.

LONG ANSWER QUESTIONS.

51. How do fossil fuels cause air pollution?

Ans: Fossil fuels are the primary source of air pollutants. The following air pollutants are produced as a result of the combustion of fossil fuels. 

1. Sulphur oxides: Sulphur is present in fossil fuels. Sulphur dioxide and sulphur trioxide are produced during burning. In the environment, these oxides react to generate sulphuric acid and sulphurous acid. These acids are damaging to the marble and erode it. 

2. Carbon oxides: Fossil fuels emit carbon monoxide and carbon dioxide. Both are carcinogenic gases. 

3. Nitrogen dioxide: Nitrogen dioxide is a smelly gas formed by the oxidation of nitric oxide. 

4. Particulate matter: Produced by autos and industry.

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

Ans: Water pollution is produced by the addition of -:

1. unfavourable compounds such as fertilisers and pesticides, as well as any harmful substances, to bodies of water.

2. sewage , entering directly into the water body. 

3. hot water from the power plant, which raises the temperature and decreases the dissolved oxygen in the water & kills aquatic life.

4. industrial effluents or radioactive chemicals found in bodies of water.

To combat water contamination, we can implement the following strategies-:

1. Sewer pipes should not be connected directly to water bodies.

2. We should not dispose of garbage or household waste in water bodies.

3. We should not dump harmful substances into water bodies.

4. Avoid washing garments near water bodies because it adds a lot of detergent to it.

5. Trees should be planted near river banks to prevent soil erosion, which contributes to the siltation of water bodies.

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

Ans: Sunlight's infrared rays travel through the window and heat the interior of the vehicle. The heat trapped within boosts the temperature of the interior since the radiation released by the upholstery and other interior sections of the car cannot flow through the glass. This is due to the fact that glass is transparent to infrared radiation from the sun with shorter wavelengths than that released by the interior of the car, which has a longer wavelength and is opaque to.

54. Justify “Dust is a pollutant”?

Ans: Because of the following reasons , dust is a pollution.

(i) Dust is made up of suspended particles. Dust inhalation produces a variety of symptoms, including allergic asthma, bronchitis, a cold, or a cough.

(ii) It decreases the light intensity.

(iii) Dust particles settle on the leaf, obstructing stomata and reducing gaseous exchange in plants.

(iv) It causes eye discomfort.

(v) Dust particles limit plant photosynthetic activity.

(vi) Smoke, fly ash, silica particles, lead, asbestos, and other contaminants can all be found in it.

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

Ans: During the day, the light warms the rocks. They compress at different rates during the night, resulting in cracks in rocks and, eventually, smaller particles.

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

Ans: Although CO2 is required by plants for carbohydrate synthesis during photosynthesis, an excessive amount of CO2 (beyond normal concentration) in the atmosphere is hazardous to living creatures and is thus classified as a pollutant. CO2 is produced within the bodies of living beings as a by-product of cellular oxidative metabolism. It diffuses out of the body via diffusion. Its overabundance inside the body is dangerous. Furthermore, an excess of CO2 concentration causes global warming (greenhouse effect) by generating an envelope around the Earth that prevents heat from the Earth's surface from escaping into the atmosphere.

Most Important Topics in Brief for NCERT Exemplar Class 9 Science Solutions Chapter 14: Natural Resources

• Resources: This Chapter covers a variety of natural resource-related aspects such as soil erosion, greenhouse gas emissions, acid rain, water pollution, rainwater harvesting, greenhouse effect, and so on.

• Natural Resources: The energy you take from the sun and the resources you can obtain on the planet are both necessary factors for all life forms on the planet to meet their fundamental needs. These natural elements are necessary for the survival of mankind.

• Atmosphere: The atmosphere is the air that surrounds the earth.

• Greenhouse Effect: To maintain the equilibrium of the greenhouse effect, this topic explains how the greenhouse effect affects nature directly or indirectly.

• Rain: The two water-related processes of evaporation and condensation work together to distribute water through a water cycle. This is when the rain begins to form. Rain is crucial for our ecosystem because it is responsible for carrying out all of the plant's agriculture activities. As a result, rainwater conservation is essential, and you can do it by installing pools, dams, and other structures.

• Acid Rain: Acid rain is created when fossil fuels are burned and various chemicals such as nitrogen dioxide and sulphur dioxide are emitted.

• Smog: Smog is a type of air pollution. It's a mixture of smoke and mist. Smog is created in any climate with high levels of air pollution, particularly in large and metropolitan areas.

• Soil Erosion: Soil erosion is the process of the upper fertile layer of soil being carried away by the wind. This is caused by natural factors such as rain and wind, as well as poor agricultural techniques and other human activities.

Some Other Points to Keep in Mind

• Rain is formed by the evaporation of water from various water bodies and its subsequent condensation.

• The wind is defined as the uneven heating of air over land and aquatic bodies.

• The rainfall pattern is completely dependent on the wind patterns.

• Water and soil contamination have an impact on quality of life. It also hurts biodiversity.

• Humans should prioritise the preservation of natural resources. They should also learn how to utilize natural resources in an environmentally friendly manner.