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
Soln:
Answer is (d) re-radiated by land and water
Explanation:
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
Soln:
Answer is (c) increase during day and decrease during night
Explanation:
Because the atmosphere prevents a lot of heat from reaching the earth’s surface. The atmosphere also prevents the escape of heat during the night. Hence the atmosphere is responsible for maintaining an ambient temperature.
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.
Soln:
Answer is (b) It will become poisonous and kill living forms
Explanation:
All the organisms living on earth require oxygen to live. If oxygen is converted to ozone, all the living beings will die.
4. One of the following factors does not lead to soil formation in nature
(a) the sun
(b) water
(c) wind
(d) polythene bags
Soln:
Answer is (d) polythene bags
Explanation:
Polythene bags pollute the soil and make it infertile.
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
Soln:
Answer is (c) ozone and oxygen
Explanation:
Ozone is an allotropic form 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
Soln:
(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
Soln:
Answer is (b) the number of water bodies in an area
Explanation:
Water bodies provide water for evaporation which is converted into clouds and bring rainfall. Lack of water bodies also reduces the humidity which will affect the rainfall pattern.
8. Among the given options, which one is not correct for the use of a 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
Soln:
Answer is (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
Soln:
Answer is (a) a biological process of nitrogen-fixing bacteria present in the soil
Explanation:
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
Soln:
Answer is (d) photosynthesis
Explanation:
Photosynthesis is a part of the carbon cycle but not 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
Soln:
Answer is (c) A change in pressure of the water bodies
Explanation:
Physical causes lead to a change in pressure on water bodies. Hence the change in water pressure will not affect the pollution of water.
12. Which of the following is not a greenhouse gas?
(a) Methane
(b) Carbon dioxide
(c) Carbon monoxide
(d) Ammonia
Soln:
Answer is (d) Ammonia
13. Which step is not involved in the carbon cycle?
(a) Photosynthesis
(b) Transpiration
(c) Respiration
(d) Burning of fossil fuels
Soln:
Answer is (b) Transpiration
Explanation:
Transpiration is the process of exhaling water from 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
Soln:
Answer is (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.
Soln:
Answer is (c) excessive use of man-made compounds containing both fluorine and chlorine
Explanation:
Carbon and fluorine react with ozone to convert it into oxygen. This results in thinning of the 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 the above
Soln:
Answer is (d) All of the above
17. When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of 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.
Soln:
Answer is (b) It comes out with the CO2 during exhalation
Explanation:
Nitrogen is the most abundant gas in nature hence while inhalation nitrogen 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.
Soln:
Answer is (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
Soln:
Answer is (b) CO2 in atmosphere → organic carbon in plants → organic carbon in animals → inorganic carbon in soil .
Explanation:
Green plants utilize atmospheric carbon-dioxide during photosynthesis to make organic compounds. When animals eat plants organic compounds will go to 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
Soln:
Answer is (a) parent rock from which soil is formed
Explanation:
Rock weathering is a process which forms soil. Rocks are naturally occurring soil aggregates which are rich in minerals. Hence rock is the source of minerals in the soil.
21. Total earth’s surface covered by water is
(a) 75%
(b) 60%
(c) 85%
(d) 50%
Soln:
Answer is (a) 75%
22. Biotic component of biosphere is not constituted by
(a) producers
(b) consumers
(c) decomposer
(d) air
Soln:
Solution is (d) air
Explanation;
Biotic component of biosphere comprises living entities, the air is a non-living component hence air is not an abiotic 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
Soln:
Answer is (d) abundance of desert plants
Explanation:
Increase in CO2 content will not favour the growth of desert plants because plants also 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
Soln:
Answer is (c) photosynthesis
Explanation:
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 these
Soln:
Answer is (b) unburnt carbon particles or hydrocarbons suspended in air
Explanation:
Unburnt carbon particles and Hydrocarbons suspend in the air to create smog. Because of smog visibility will be low in cold weather.
26. Growth of Lichens on barren rocks is followed by the growth of
(a) moss
(b) ferns
(c) gymnosperms
(d) algae
Soln:
Answer is (a) moss
Explanation:
Lichens release certain enzymes which makes the rock suitable for the growth of moss. Further moss leads to the formation of soil which will allow higher plants to grow.
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.
Soln:
Answer is (a) breeding of animals
Explanation:
Most aquatic animals are cold-blooded. Their egg and larvae are highly susceptible to temperature changes hence breeding of animals gets affected by temperature changes.
28. Soil erosion can be prevented by
(a) raising forests
(b) deforestation
(c) excessive use of fertilizer
(d) overgrazing by animals
Soln:
Answer is (a) raising forests
Explanation:
Trees in the forest hold on the soil by its roots. Hence growing forest can prevent soil erosion.
29. What happens when rain falls on soil without vegetational cover?
(a) Rainwater percolates in soil efficiently
(b) Rainwater causes loss of surface soil
c) Rainwater leads to fertility of the soil
(d) Rainwater does not cause any change in soil
Explanation:
b) Rainwater causes loss of surface soil
Explanation:
Roots hold on the surface soil and help them to get washed away from the current of water due to rainfall. When there is no vegetation surface soil gets washed away.
30. Oxygen is harmful for
(a) ferns
(b) nitrogen-fixing bacteria
(c) chara
(d) mango tree
Soln:
Answer is (b) nitrogen-fixing bacteria
Explanation:
Nitrogen-fixing bacteria are anaerobic, they get killed when exposed to oxygen hence oxygen is harmful to them.
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