NCERT Exemplar Solution CBSE Class 10 
                                Science (Biology) 
                          Chapter 15 – Our Environment 
         
        Multiple Choice Questions 
         
        1. Which one of the following is an artificial ecosystem? 
        (a) Pond 
        (b) Crop field 
        (c) Lake 
        (d) Forest 
        Ans: The answer is (b) Crop field. A crop field is a man-made ecosystem. 
         
        2. In a food chain, the third trophic level is always occupied by 
        (a) carnivores 
        (b) herbivores 
        (c) decomposers 
        (d) producers 
        Ans: The answer is (a) carnivores. The first trophic level is producers, the second 
        trophic level is herbivores, the third trophic level is occupied by carnivores. 
         
        3. An ecosystem includes 
        (a) all living organisms 
        (b) non-living objects 
        (c) both living organisms and non-living objects 
        (d) sometimes living organisms and sometimes non-living objects 
        Ans: The answer is (c) both living organisms and non-living objects. An ecosystem is 
        a complex of living and nonliving organisms and their interactions. 
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      4. In the given food chain, suppose the amount of energy at the fourth trophic 
      level is 5 kJ, what will be the energy available at the producer level? 
      Grass → Grasshopper → Frog → Snake → Hawk 
      (a) 5 k J 
      (b) 50 k J 
      (c) 500 k J 
      (d) 5000 k J 
      Ans: The answer is (d) 5000 k J. The amount of energy available at one trophic level 
      is ten times that of the following trophic level. As a result, energy at the third trophic 
      level is 50kj. The energy of the second level trophic level (Producer) is 500 KJ, 
      whereas the energy of the first level trophic level (Producer) is 5000 KJ. 
       
      5. Accumulation of non-biodegradable pesticides in the food chain in increasing 
      amounts at each higher trophic level is known as 
      (a) eutrophication 
      (b) pollution 
      (c) biomagnification 
      (d) accumulation 
      Ans: The answer is (c) bio magnification. Nutrient richness over the optimal amount 
      is referred to as eutrophication. Runoff from the land causes eutrophication. Unwanted 
      material is released into the environment. Pollution has a negative impact on living 
      beings. 
       
      6. Depletion of ozone is mainly due to 
      (a) chlorofluorocarbon compounds 
      (b) carbon monoxide 
      (c) methane 
      (d) pesticides 
      Ans:  
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      The answer is (a) chlorofluorocarbon compounds. The contained chlorofluorocarbons 
      are broken down by UV light in the stratosphere, releasing chlorine. The chlorine 
      depletes the ozone layer by reacting with it. Thus, chlorofluorocarbon chemicals are 
      the primary cause of ozone depletion. 
       
      7. Organisms that synthesize carbohydrates from inorganic compounds using 
      radiant energy are called 
      (a) decomposers 
      (b) producers 
      (c) herbivores 
      (d) carnivores 
      Ans: The answer is (b) producers. Producers use solar energy to synthesize food from 
      water and carbon-di-oxide. Plants and a few micro-organisms are the producers. 
      Organisms that decompose organic material are called decomposers. Herbivores are 
      the organisms that feed on plant and their products. Carnivores are the ones that feed 
      on other organisms. 
       
      8. In an ecosystem, the 10% of energy available for transfer from one trophic 
      level to the next is in the form of 
      (a) heat energy 
      (b) light energy 
      (c) chemical energy 
      (d) mechanical energy 
      Ans: The answer is (c) chemical energy. In the form of food, energy may be 
      transferred from one trophic level to the next. Food is a type of chemical energy. 
       
      9. Organisms of a higher trophic level that feed on several types of organisms 
      belonging to a lower trophic level constitute the 
      (a) food web 
      (b) ecological pyramid 
      (c) ecosystem 
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      (d) food chain 
      Ans: The answer is (a) food web. A food chain is a group of organisms through which 
      food energy moves in an ecosystem. An ecosystem is made up of all the live creatures 
      in a given area as well as the non-living components of their surroundings. Ecological 
      pyramids are a visual representation of the trophic structure and energy transfer in an 
      ecosystem. The food web is made up of higher trophic level species that feed on 
      different sorts of lower trophic level organisms. 
       
      10. Flow of energy in an ecosystem is always 
      (a) unidirectional 
      (b) bidirectional 
      (c) multidirectional 
      (d) no specific direction 
      Ans: The answer is (a) unidirectional. The flow of energy is from prey to predator and 
      it cannot be in the reverse direction. Hence the flow of energy is uni-directional. 
       
      11. Excessive exposure of humans to U V-rays results in 
      (i) damage to the immune system 
      (ii) damage to lungs 
      (iii) skin cancer 
      (iv) peptic ulcers 
      (a) (i) and (ii) 
      (b) (ii) and (iv) 
      (c) (i) and (iii) 
      (d) (iii) and (iv) 
      Ans: The answer is (c) (i) and (iii). The upper layer of our bodies is affected by UV 
      radiation. UV rays cause skin cancer, and their impact on the skin has an impact on 
      our immune system since the skin is the primary level of the immunological barrier. 
       
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