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NCERT Exemplar · Class 10 Science How do Organisms Reproduce?

58 questions · 58 still being checked

Multiple Choice Questions 11–20 (part 2 of 6)

  1. Exercise 11

    The number of chromosomes in parents and offsprings of a particular species remains constant due to
    (a)
    doubling of chromosomes after zygote formation
    (b)
    halving of chromosomes during gamete formation
    (c)
    doubling of chromosomes after gamete formation
    (d)
    halving of chromosomes after gamete formation

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    (b)
    (b) Halving of chromosomes during gamete formation.\[2n \xrightarrow{\text{meiosis}} n \quad (\text{gametes}) \] \[n + n \xrightarrow{\text{fertilisation}} 2n \quad (\text{zygote}) \]Meiosis halves the number; fertilisation restores it.

  2. Exercise 12

    In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called
    (a)
    filaments
    (b)
    hyphae
    (c)
    rhizoids
    (d)
    roots

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    NCERT’s answer
    (b)
    (b) Hyphae.In Rhizopus (bread mould) the fungal body is a mass of thread-like tubular filaments called hyphae; sporangia develop at their tips.

  3. Exercise 13

    Vegetative propagation refers to formation of new plants from
    (a)
    stem, roots and flowers
    (b)
    stem, roots and leaves
    (c)
    stem, flowers and fruits
    (d)
    stem, leaves and flowers

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    (b)
    (b) Stem, roots and leaves.Potato tubers (stem), sweet potato (root) and Bryophyllum (leaf) all sprout new plantlets without seeds — true vegetative propagation.

  4. Exercise 14

    Factors responsible for the rapid spread of bread mould on slices of bread are
    (i)
    large number of spores
    (ii)
    availability of moisture and nutrients in bread
    (iii)
    presence of tubular branched hyphae
    (iv)
    formation of round shaped sporangia
    (a) (i) and (iii)
    (b)(ii)
    and iv)
    (c) (i) and (ii)
    (d) (iii) and (iv)

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    (c)
    (c) (i) and (ii).Hyphae and sporangia are the mould's fixed structure, always present; rapid spread needs a large number of spores plus moisture and nutrients to germinate.

  5. Exercise 15

    Length of pollen tube depends on the distance between
    (a)
    pollen grain and upper surface of stigma
    (b)
    pollen grain on upper surface of stigma and ovule
    (c)
    pollen grain in anther and upper surface of stigma
    (d)
    upper surface of stigma and lower part of style

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    (b)
    (b) Pollen grain on stigma and ovule. The tube grows down the style from the germinated grain on the stigma to the ovule, carrying male gametes; that path is its length.

  6. Exercise 16

    Which of the following statements are true for flowers?
    (i)
    Flowers are always bisexual
    (ii)
    They are the sexual reproductive organs
    (iii)
    They are produced in all groups of plants
    (iv)
    After fertilisation they give rise to fruits
    (a) (i) and (iv)
    (b) (ii) and (iii)
    (c) (i) and (iii)
    (d) (ii) and (iv)

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    (d)
    (d) (ii) and (iv). Flowers are the sexual organs, and post-fertilisation the ovary matures into fruit; many flowers are unisexual and only angiosperms bear them, so (i) and (iii) fail.

  7. Exercise 17

    Which among the following statements are true for unisexual flowers?
    (i)
    They possess both stamen and pistil
    (ii)
    They possess either stamen or pistil
    (iii)
    They exhibit cross pollination
    (iv)
    Unisexual flowers possessing only stamens cannot produce fruits
    (a) (i) and (iv)
    (b) (ii), (iii) and (iv)
    (c) (iii) and (iv)
    (d) (i), (iii) and (iv)

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    NCERT’s answer
    (b)
    (b) (ii), (iii) and (iv). A unisexual flower carries only stamen or only pistil, so pollination must be cross; a stamen-only flower has no ovary and so sets no fruit.

  8. Exercise 18

    Which among the following statements are true for sexual reproduction in flowering plants?
    (i)
    It requires two types of gametes
    (ii)
    Fertilisation is a compulsory event
    (iii)
    It always results in formation of zygote
    (iv)
    Offspring formed are clones
    (a) (i) and (iv)
    (b) (i), (ii) and (iv)
    (c) (i), (ii) and (iii)
    (d) (i), (ii) and (iv)

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    (c)
    (c) (i), (ii) and (iii). Sexual reproduction needs male and female gametes, fertilisation always occurs and always forms a zygote; but the zygote mixes two genomes, so offspring are not clones.

  9. Exercise 19

    In Figure 8.1\displaystyle 8.1, the parts A, B and C are sequentially
    (a)
    cotyledon, plumule and radicle
    (b)
    plumule, radicle and cotyledon
    (c)
    plumule, cotyledon and radicle
    (d)
    radicle, cotyledon and plumule
    NCERT_Question_Class10_Science_Exemplar_Ch8_Q19

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    (c)
    (c) Plumule, cotyledon, radicle. A marks the small tip above the cotyledons, B a cotyledon lobe, C the tip below -- shoot, storage leaf and root primordia of the embryo.

  10. Exercise 20

    Offspring formed as a result of sexual reproduction exhibit more variations because
    (a)
    sexual reproduction is a lengthy process
    (b)
    genetic material comes from two parents of the same species
    (c)
    genetic material comes from two parents of different species
    (d)
    genetic material comes from many parents

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    (b)
    (b) Genetic material comes from two parents of the same species. Fertilisation mixes maternal and paternal chromosomes into a new combination, so offspring differ from both parents and from each other.