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Growth of Lichens on barren rocks is followed by the growth of (a) moss (b) ferns (c) gymnosperms algae

Soln: Answer is (a) moss Explanation: Lichens releases certain enzymes which makes the rock suitable for the growth of moss. Further moss lead to the formation of soil which will allow higher plants to grow.

ScienceClass 9CBSE

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 none of these

Soln: Answer is (b) unburnt carbon particles or hydrocarbons suspended in air Explanation: Unburnt carbon particles and Hydrocarbons suspend in air to create smog. Because of smog visibility will be low in cold weather.

ScienceClass 9CBSE

Oxygen is returned to the atmosphere mainly by (a) burning of fossil fuel (b) respiration (c) photosynthesis fungi

Soln: Answer is (c) photosynthesis Explanation: Plants take CO2 from environment and they return back oxygen by a process called photosynthesis.

ScienceClass 9CBSE

An increase in carbondioxide 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 abundance of desert plants

Soln: Answer is (d) abundance of desert plants Explanation: Increase in CO2 content will not favor growth of desert plants because plants also require, oxygen, minerals and water to growth and development.

ScienceClass 9CBSE

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

ln: Solution is (d) air Explanation; Biotic component of biosphere comprise of living entities, air is a non-living component hence air is not a biotic component.

ScienceClass 9CBSE

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

Soln: Answer is (a) 75% Explanation: 96.5% of the water is found in sea’s and oceans , 17% is groundwater, 1.7% in icecaps and glaciers. 0.001% as vapor and 2.5% fresh water.

ScienceClass 9CBSE

Major source of mineral in soil is the (a) parent rock from which soil is formed (b) plants (c) animals 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.

ScienceClass 9CBSE

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 in-organic carbon.

ScienceClass 9CBSE

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.

ScienceClass 9CBSE

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.

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 Nitrogen is not utilized by our body and it is exhaled along with carbon-di-oxide.

ScienceClass 9CBSE

Which of the following is a recently originated problem of environment? (a) Ozone layer depletion (b) Green house effect (c) Global warming All of the above

Soln: Answer is (d) All of the above

ScienceClass 9CBSE

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 reacts with ozone to convert it into oxygen. This results in thinning of ozone lays which is called as ozone depletion.

ScienceClass 9CBSE

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 thickening of ozone in the ozone layer

Soln: Answer is (b) thinning of the ozone layer

ScienceClass 9CBSE

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

Answer is (b) Transpiration Explanation: Transpiration is the process of exhaling water from trees. Transpiration is a part of water cycle.

ScienceClass 9CBSE

Which of the following is not a green house gas? (a) Methane (b) Carbon dioxide (c) Carbon monoxide Ammonia

Soln: Answer is (d) Ammonia

ScienceClass 9CBSE

1. One of the following processes is not a step involved in the water-cycle operating in nature (a) evaporation (b) transpiration (c) precipitation photosynthesis

Answer is (d) photosynthesis Explanation: Photosynthesis is a part of carbon cycle but not water cycle.

ScienceClass 9CBSE

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 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 change in pressure on water bodies. Hence change in water pressure will not affect pollution of water.

ScienceClass 9CBSE

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 the plants used as cereal crops in field

Answer is (a) a biological process of nitrogen fixing bacteria present in soil Explanation: Cereal plants cannot fix the nitrogen on their own. They comprise of bacteria in their root nodules which will convert nitrates to nitrites. This process is called as nitrogen fixation.

ScienceClass 9CBSE

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 adversally affect the useful component from the soil They destroy the soil fertility

Soln: Answer is (a) They are eco-friendly

ScienceClass 9CBSE

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 are converted into clouds and bring rainfall. Lack of water bodies also reduce the humidity which will affect the rainfall pattern.

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