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NCERT Exemplar · Class 10 Science Our Environment

38 questions · 38 still being checked

Multiple Choice Questions 11–21 (part 2 of 4)

  1. Exercise 11

    Excessive exposure of humans to U V-rays results in
    (i)
    damage to 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)

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    NCERT’s answer
    (c)
    (c) (i) and (iii). \(\displaystyle UV\uparrow \Rightarrow\) immune suppression and skin-cell DNA damage \(\displaystyle \Rightarrow\) skin cancer. UV does not reach the lungs or stomach lining, so (ii) and (iv) are ruled out.

  2. Exercise 12

    In the following groups of materials, which group (s) contains only non-biodegradable items?
    (i)
    Wood, paper, leather
    (ii)
    Polythene, detergent, PVC
    (iii)
    Plastic, detergent, grass
    (iv)
    Plastic, bakelite, DDT
    (a)(iii)
    (b)(iv)
    (c) (i) and (iii)
    (d) (ii) and (iv)

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    NCERT’s answer
    (d)
    (d) (ii) and (iv). Polythene, detergent, PVC, plastic, bakelite and DDT are synthetic or persistent compounds microbes cannot break down; wood, paper, leather and grass are natural and biodegradable.

  3. Exercise 13

    Which of the following limits the number of trophic levels in a food chain?
    (a)
    Decrease in energy at higher trophic levels
    (b)
    Dufficient food supply
    (c)
    Polluted air
    (d)
    Water

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    NCERT’s answer
    (a)
    (a) Decrease in energy at higher trophic levels. \[E_n = E_0\,(0.10)^n \] Energy shrinks tenfold at each transfer, so beyond $\displaystyle 4$-$\displaystyle 5$ trophic levels too little remains to support a further consumer.

  4. Exercise 14

    Which of the statement is incorrect?
    (a)
    All green plants and blue green algae are producers
    (b)
    Green plants get their food from organic compounds
    (c)
    Producers prepare their own food from inorganic compounds
    (d)
    Plants convert solar energy into chemical energy

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    NCERT’s answer
    (b)
    (b) Green plants get their food from organic compounds. Producers are autotrophs: they synthesise food from inorganic raw materials \(\displaystyle \mathrm{CO_2}\), \(\displaystyle \mathrm{H_2O}\) using solar energy, never from organic compounds.

  5. Exercise 15

    Which group of organisms are not constituents of a food chain?
    (i)
    Grass, lion, rabbit, wolf
    (ii)
    Plankton, man, fish, grasshopper
    (iii)
    Wolf, grass, snake, tiger
    (iv)
    Frog, snake, eagle, grass, grasshopper
    (a) (i) and (iii)
    (b) (iii) and (iv)
    (c) (ii) and (iii)
    (d) (i) and (iv)

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    NCERT’s answer
    (c)
    (c) (ii) and (iii). (i) and (iv) form valid feeding sequences; grasshopper does not link with plankton, fish and man, and wolf, grass, snake, tiger share no single trophic order.

  6. Exercise 16

    The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about
    (a)
    1\displaystyle 1 % (b) 5\displaystyle 5 % (c) 8\displaystyle 8 % (d) 10\displaystyle 10 %

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    NCERT’s answer
    (a)
    (a) $\displaystyle 1$%. Only about $\displaystyle 1$% of the incident solar radiation is captured by chlorophyll and used in photosynthesis; the rest is reflected, transmitted, or lost as heat.

  7. Exercise 17

    In the given Figure 15.1\displaystyle 15.1 the various trophic levels are shown in a pyramid. At which trophic level is maximum energy available?
    (a)
    T4\displaystyle \mathrm{T}_4
    (b)
    T2\displaystyle \mathrm{T}_2
    (c)
    T1\displaystyle \mathrm{T}_1
    (d)
    T3\displaystyle \mathrm{T}_3
    NCERT_Question_Class10_Science_Exemplar_Ch15_Q17

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    NCERT’s answer
    (c)
    (c) \(\displaystyle T_1\). At each transfer \[T_1 \xrightarrow{10\%} T_2 \xrightarrow{10\%} T_3 \xrightarrow{10\%} T_4 \] about $\displaystyle 90$% of the energy is lost as heat at every step, so the producer level \(\displaystyle T_1\), the pyramid's base, holds the most energy.

  8. Exercise 18

    What will happen if deer is missing in the food chain given below?
    Grass → Deer → Tiger
    (a)
    The population of tiger increases
    (b)
    The population of grass decreases
    (c)
    Tiger will start eating grass
    (d)
    The population of tiger decreases and the population of grass increases

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    NCERT’s answer
    (d)
    (d) Population of tiger decreases and population of grass increases. \[\text{Deer absent} \Rightarrow \text{Tiger}\downarrow\text{ (no prey)}, \;\text{Grass}\uparrow\text{ (ungrazed)} \]

  9. Exercise 19

    The decomposers in an ecosystem
    (a)
    convert inorganic material, to simpler forms
    (b)
    convert organic material to inorganic forms
    (c)
    convert inorganic materials into organic compounds
    (d)
    do not breakdown organic compounds

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    NCERT’s answer
    (b)
    (b) Convert organic material to inorganic forms. \[\text{Organic matter (dead remains)} \xrightarrow{\text{decomposers}} \mathrm{CO_2} + \mathrm{H_2O} + \text{minerals} \] returning nutrients to the soil.

  10. Exercise 20

    If a grass hopper is eaten by a frog, then the energy transfer will be from
    (a)
    producer to decomposer
    (b)
    producer to primary consumer
    (c)
    primary consumer to secondary consumer
    (d)
    secondary consumer to primary consumer

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    NCERT’s answer
    (c)
    (c) Primary consumer to secondary consumer. \[\text{Grass (producer)} \to \text{Grasshopper (primary consumer)} \to \text{Frog (secondary consumer)} \] the frog gains energy from the grasshopper, not directly from the plant.

  11. Exercise 21

    Disposable plastic plates should not be used because
    (a)
    they are made of materials with light weight
    (b)
    they are made of toxic materials
    (c)
    they are made of biodegradable materials
    (d)
    they are made of non-biodegradable materials

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    NCERT’s answer
    (d)
    (d) They are made of non-biodegradable materials. Microbes cannot break plastic down, so it persists in soil and water instead of decomposing like natural waste.