NCERT Exemplar Solutions for Class 9 Science Chapter 14 Natural Resources (MCQ, SAQ and LAQ)
Chapter Name | NCERT Exemplar Solutions for Class 9 Science Ch 14 Natural Resources |
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Objective Type Questions for Natural Resources
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
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
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
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
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
(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
(a) Evaporation
(b) Transpiration
(c) Precipitation
(d) Photosynthesis
Solution
(d) Photosynthesis
(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
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
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
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
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
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
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
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
24. Oxygen is returned to the atmosphere mainly by :
(a) Burning of fossil fuel
(b) Respiration
(c) Photosynthesis
(d) Fungi
Solution
(c) 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
26. Growth of lichens on barren rocks is followed by the growth of :
(a) moss
(b) ferns
(c) gymnosperms
(d) algae
Solution
(a) moss
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
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
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
30. Oxygen is harmful for :
(a) ferns
(b) nitrogen fixing bacteria
(c) chara
(d) mango tree
Solution
(b) nitrogen fixing bacteria
Short Answer Questions for Natural Resources
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. As water flows through rocks which have certain soluble minerals, some of them get dissolved in the water. 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 :
- Plantation: Plants and trees protect soil erosion by binding soil by roots.
- Proper drainage system: Root systems stabilizes the soil and prevents soil erosion.
- By crop rotation farming : It maintains the fertility water holding capacity of the soil. Thus, it prevents soil erosion.
- By preventing excessive grazing by animals.
- Prevent deforestation.
33. How is the life of organisms living in water affected when water gets polluted?
Solution
Almost all types of water pollutants affect the life of living in water.
- Eutrophication : 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. Dying algae feed microorganisms, which deplete more oxygen.
- Thermal waste water discharge : 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.
- Bio-magnification : 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
Lichens and mosses release substances which help to break down the stones and helps in the formation of soil.
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
- Abiotic factors making soil — Sun, water, 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.
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
The oxygen cycle, nitrogen cycle and carbon cycle and water cycle take place continuously in nature by the constant interaction between the biotic (plants, trees, animals, lichens, mosses, etc.) and abiotic components (Sun, water, wind, etc.) of the biosphere. These interactions consist of a transfer of matter and energy between the different components of the biosphere. Thus, their levels in the atmosphere are maintained constantly upto the required limit.
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
Atmosphere act as a temperature buffer on Earth as it is bad conductor of heat but Moon does not have atmosphere. Thus, Moon gets heated up in the daytime when sunlight falls on its surface. It causes sudden increase in temperature during the daylight hours and similarly cools when there is absence of sunlight.
41. Why do people love to fly kites near the seashore?
Solution
The land gets heated up faster than the sea or other water bodies. Due to this uneven heating of land and sea there is movement of air leading to the formation of wind. The air above land gets heated faster and being light and starts rising up. As the air rises, 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. Therefore, there is regular flow of cool air from sea towards the land during daytime. This movement of air 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 is situated very near to Taj Mahal. This refinery releases toxic gases that contain sulphur and nitrogen oxides which cause acid rain. Acid rain reacts with the marble (calcium carbonate) of Taj Mahal. It is the reason of corrosion of the marbles by forming a fungus known as ‘marble cancer’. Suspended particulate matter (dust and exhaust) are causing the discoloration of the Taj Mahal.
43. Why do not lichens occur in Delhi whereas they commonly grow in Manali or Darjeeling?
Solution
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. Moreover, Delhi occurs in semi-arid area where atmospheric moisture is low. 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 Earth’s water is salty or permanently frozen which is not suitable for drinking. Only three percent of all the water is fresh water, and one percent is available for drinking water. The other two percent is in the form of ice caps and glaciers. Fresh water is found in ice, lakes, rivers, streams and underground. Moreover, most of the sources of water supply are contaminated by industrial waste or sewage. So, we are relying on such a small percentage of all the water on Earth. 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 :
- Fertilizer pollution does not make fish grow bigger, for example : fertilizers, whether they are artificial or organic, can cause serious problems if they contaminate freshwater and marine ecosystems.
- Eutrophication : Euthrophication is the enrichment of a water body with nutrients, usually with an excess amount of nutrients. The nutrients in fertilizers cause rapid growth of algae, also known as an algal bloom. Blooms cover the surface of the water so sunlight does not reach as far down and deplete more oxygen. This leads to the death of most of the water animals as fishes.
- Thermal waste water discharge : 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.
- Addition of poisonous compounds in water.
- Domestic Sewage : 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 are called pioneer colonisers of bare rock because they release substances which break down the stones resulting in the 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 gets into the cracks in the rocks. If this water later freezes, it would cause the cracks to widen. This helps in the weathering of rocks.
(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 the complex dead bodies of animals and plants into simpler substance called humus. Humus is a dark coloured colloidal material that makes the organic components of soil. 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 roo nodules useful for the plants ?
Solution
Nitrogen fixing rhizobium bacteria are present in root nodules which fix the atmospheric nitrogen into nitrate which help the plants for its growth. The plants use this nitrogen to synthsize proteins and other materials.
Long Answer Questions for Natural Resources
51. How do fossil fuels cause air pollution?
Solution
The fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur. When these fuels are burnt, nitrogen and sulphur too are burnt and this produces different oxides of nitrogen and sulphur. Not only is the inhalation of these gases dangerous, they also dissolve in rain to give rise to acid rain. The combustion of fossil fuels also increases the amount of suspended particles in air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons. Presence of high levels of all these pollutants causes visibility to be lowered, especially in cold weather when water also condenses out of air. This is known as smog and is a visible indication of air pollution.
52. What are the causes of water pollution? Discuss how you can contribute in reducing water pollution.
Solution
Cause of Water Pollution – Water pollution can be caused by addition of :
- (i) Undesirable substances- Any poisonous substances like fertilizers and pesticides.
- (ii) Sewage waste.
- (iii) Thermal waste water discharge- The hot water from the power plant that increases the temperature and reduces the dissolved oxygen in water.
- (iv) Industrial radioactive substances in water body.
- By using natural fertilizers and pesticides as far as possible.
- Restrain from throwing litter into any water body.
- Proper sewage drainage system.
- Avoid washing of clothes near water bodies as it adds lot of detergents to it.
- Plantation near water bodies to stop soil erosion.
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 glass and heats the interior of the car. The upholstery and inner parts of the car emits radiation that cannot pass out of the glass, so the heat trapped inside the car and raise the temperature of the interior of the car.
54. Justify “Dust is a pollutant”.
Solution
Dust remains present in the air as suspended particles. It covers the stomata on the leaf surface and blocks them thereby reducing the exchange of gaseous substances. It also can cause allergy, other respiratory diseases, cancer and heart diseases. Therefore, we can say that dust is a pollutant.
55. Explain the role of the Sun in the formation of soil.
Solution
During the day rocks expand as Sun heats up rocks and in night, these rocks cool down and contract. But all parts of the rock do not expand and contract at the same rate, so formation of cracks and ultimately break up of rocks into smaller pieces can be seen.
56. Carbon dioxide is necessary for plants. Why do we consider it as a pollutant?
Solution
Carbon dioxide is one of the greenhouse gases. An increase in the carbon dioxide gas stops escaping heat from the atmosphere that increase the temperature of atmosphere and lead to global warming.