Class 10 Science · Chapter 7

How do Organisms Reproduce?

434 Class 10 Science questions on How do Organisms Reproduce? from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 10 of 22

1. Q181 CBSE 2024
   A zygote is formed by ​the ​fusion of ​a male gamete and a female ​gamete. The ​number of chromosomes in the ​zygote ​of a human is :

   1. (a)23
   2. (b)44
   3. (c)46
   4. (d)92
   Show answer

   (c) 46

   Step-by-step solution →
2. Q182 CBSE 2024
   Select ​from the following the conditions responsible for the rapid spread of bread mould on ​a slice of bread :

   1. (i)Formation of ​large number of spores
   2. (ii)Presence of moisture ​and nutrients ​in bread
   3. (iii)​Low temperature
   4. (iv)​Presence of hyphae

   1. (a)(i) and (ii)
   2. (b)(ii) and (iv)
   3. (c)(ii) and (iii)
   4. (d)(iii) and (iv)
   Show answer

   (a) (i) and (ii)

   Step-by-step solution →
3. Q183 CBSE 2024
   Identify ​the mode of ​asexual reproduction ​in ​the ​following organism :

   1. (a)Fragmentation
   2. (b)Multiple fission
   3. (c)Budding
   4. (d)Binary fission
   Show answer

   (c) Budding

   Step-by-step solution →
4. Q184 CBSE 2024
   Which one of the following organism ​is ​represented ​by ​this diagram ?

   1. (a)Spirogyra
   2. (b)Planaria
   3. (c)Yeast
   4. (d)Rhizopus
   Show answer

   (d) Rhizopus

   Step-by-step solution →
5. Q185 CBSE 2024
   Offsprings formed ​as ​a result of ​sexual ​reproduction produce more ​variations ​because

   1. (a)genetic material is contributed by many parents.
   2. (b)sexual reproduction is a lengthy process.
   3. (c)genetic material is contributed by two individuals of same species to produce a new generation.
   4. (d)DNA copying is not accompanied by the creation of cellular apparatus.
   Show answer

   (c) genetic material is contributed by two individuals of same species to produce a new generation.

   Step-by-step solution →
6. Q186 CBSE 2024
   In ​bread mould, ​the structures labelled ​A ​and B respectively ​are ​:

   1. (a)hyphae and spore
   2. (b)root and sporangium
   3. (c)hyphae and sporangium
   4. (d)root and spores
   Show answer

   (c) hyphae and sporangium

   Step-by-step solution →
7. Q187 CBSE 2024
   Which ​one of ​the following organ is ​NOT ​a ​part of ​human ​female ​reproductive system ?

   1. (a)Ovary
   2. (b)Uterus
   3. (c)Vas deferens
   4. (d)Fallopian tube
   Show answer

   (c) Vas deferens

   Step-by-step solution →
8. Q188 CBSE 2024
   The part of a ​seed that stores food, the ​future ​root and the ​future ​shoot ​respectively are :

   1. (a)Plumule, radicle, cotyledon
   2. (b)Cotyledon, plumule, radicle
   3. (c)Cotyledon, radicle, plumule
   4. (d)Radicle, plumule, cotyledon
   Show answer

   (c) Cotyledon, radicle, plumule

   Step-by-step solution →
9. Q189 CBSE 2024
   In ​which ​of the following organisms, multiple fission ​is a ​means of asexual reproduction ?

   1. (a)Yeast
   2. (b)Leishmania
   3. (c)Paramoecium
   4. (d)Plasmodium
   Show answer

   (d) Plasmodium

   Step-by-step solution →
10. Q190 CBSE 2024
    Q. ​Nos. 17 to 20 consists ​of ​two statements ​– Assertion (A) and Reason (R), answer ​these ​questions selecting the appropriate ​option given below ​:

    Assertion (A): Offsprings produced by asexual reproduction are genetically similar to the parents.

    Reason (R): Asexual reproduction involves a single parent.

    1. (a)Both (A) and (R) are true and (R) is the correct explanation of (A).
    2. (b)Both (A) and (R) are true and (R) is not correct explanation of (A).
    3. (c)(A) is true, but (R) is false.
    4. (d)(A) is false, but (R) is true.
    Show answer

    (a) Both (A) and (R) are true and (R) is the correct explanation of (A).

    Step-by-step solution →
11. Q191 CBSE 2024
    “Stability of ​DNA in a ​species is ​ensured ​during ​sexual reproduction.” ​Justify the ​statement.
    Show answer

    Germ cells form with half the chromosomes and DNA, and fertilisation restores the full number, so the DNA content stays constant.

    In sexual reproduction a new individual is formed by the fusion of two germ cells, one from each parent. If the germ cells carried the full amount of DNA, the DNA would double in every generation. This is prevented because germ cells are formed by meiosis and have only half the number of chromosomes and half the amount of DNA of the body cells. At fertilisation the two halves combine, so the zygote gets back the original number of chromosomes and the original amount of DNA — in humans, a sperm with $23$ chromosomes and an egg with $23$ give a zygote with $23+23=46$, the same as in each parent's body cells. Hence the DNA content of the species stays constant from one generation to the next.

    Step-by-step solution →
12. Q192 CBSE 2024
    Name ​two ​types of germ ​cells ​present in human beings. List two structural differences ​between the two.
    Show answer

    The germ cells are the sperm and the egg; the sperm is very small with a tail, the egg much larger with no tail.

    The two germ cells are the sperm (male germ cell) and the egg or ovum (female germ cell). Structural differences (any two): the sperm is very small, while the egg is much larger; the sperm has a long tail and is motile, while the egg has no tail and does not move on its own; the egg contains stored food, while the sperm carries mainly genetic material and no food store.

    Step-by-step solution →
13. Q193 CBSE 2024
    The ​survival of ​a ​species is ​promoted through creation of ​variations. Illustrate ​with ​an example.
    Show answer

    Variations help some individuals survive a drastic change in surroundings, so the species continues; for example, heat-resistant bacteria survive warming water.

    Variations arise during reproduction because DNA copying is never absolutely accurate (and sexual reproduction combines DNA from two parents), so individuals of a population differ slightly. If the surroundings change drastically, individuals without a suitable variation may die, but those that happen to carry one survive. Example: in a population of bacteria living in temperate waters, if the water temperature rises (for instance by global warming), most of the bacteria die, but the few variants resistant to heat survive and multiply. These variants keep the species going — so variation promotes the survival of a species over time.

    Step-by-step solution →
14. Q194 CBSE 2024
    Some ​unicellular organisms such as Plasmodium and ​Leishmania differ in ​the ​manner in which they reproduce. Name and explain ​the ​reproductive process taking ​place in them.
    Show answer

    Leishmania reproduces by binary fission in a definite plane; Plasmodium reproduces by multiple fission into many daughter cells at once.

    Leishmania reproduces by binary fission: the parent cell divides into two daughter cells, and because it has a whip-like flagellum at one end, the division takes place in a definite plane (lengthwise) in relation to that flagellum. Plasmodium reproduces by multiple fission: its nucleus divides repeatedly and the parent cell then divides into many daughter cells simultaneously.

    Step-by-step solution →
15. Q195 CBSE 2024
    Identify the organ in the ​human female ​reproductive ​system where the sperm encounters the egg cell. ​What will happen if it is blocked ​? Name ​the technique by ​which it ​can be blocked.
    Show answer

    Fertilisation occurs in the oviduct; if it is blocked, fertilisation cannot occur, and the technique is tubectomy.

    The sperm encounter the egg in the oviduct (fallopian tube), where fertilisation takes place. If the oviduct is blocked, the sperm cannot reach the egg and the egg cannot reach the uterus, so fertilisation does not take place and pregnancy is prevented. The oviducts are blocked by a surgical method called tubectomy.

    Step-by-step solution →
16. Q196 CBSE 2024
    What ​is vegetative ​propagation ? List ​its two ​advantages.
    Show answer

    Vegetative propagation raises new plants from roots, stems or leaves; they flower earlier and are genetically similar to the parent.

    Vegetative propagation is a mode of asexual reproduction in which new plants are obtained from vegetative parts of a plant - the root, stem or leaves - instead of from seeds. Advantages (any two): (1) Plants raised this way bear flowers and fruits earlier than those produced from seeds. (2) All the plants produced are genetically similar to the parent plant and have all its characteristics. (3) Plants that have lost the capacity to produce seeds, such as banana, orange, rose and jasmine, can still be propagated.

    Step-by-step solution →
17. Q197 CBSE 2024
    List ​two ​distinguishing features ​between sexual reproduction ​and ​asexual ​reproduction.
    Show answer

    Asexual reproduction needs one parent and no gametes, whereas sexual reproduction usually needs two parents and involves fusion of gametes.

    Any two of the following: (1) Number of parents: asexual reproduction involves only one parent; sexual reproduction usually involves two parents, a male and a female. (2) Gametes: in asexual reproduction no gametes are formed and there is no fertilisation; in sexual reproduction male and female gametes are formed and fuse (fertilisation) to form a zygote. (3) Variation: offspring of asexual reproduction are nearly identical to the parent; offspring of sexual reproduction show variation because they receive DNA from two parents.

    Step-by-step solution →
18. Q198 CBSE 2024
    1. (a)In angiosperms why fertilisation cannot take place in flowers if pollination does ​not take ​place ? Where is ​zygote located in a flower after fertilisation ? What does it develop into ?
    2. (b)Write the names of those parts of a flower which serve ​the same ​function as the following do in animals : (i) ​testis (ii) ​ovary
    Show answer

    Fertilisation needs pollination so the pollen tube can reach the ovule; the zygote in the ovule forms an embryo.

    (a) The male germ cells are inside the pollen grains made in the anther, while the female germ cell (egg) is inside the ovule in the ovary. Only after pollination, the transfer of pollen to the stigma, can a pollen tube grow from the pollen grain through the style to the ovule and deliver the male germ cell; without pollination the two germ cells never meet, so fertilisation cannot take place. After fertilisation the zygote is located inside the ovule, within the ovary, and it divides to form an embryo; the ovule becomes the seed and the ovary the fruit. (b) (i) Testis: the anther of the stamen, which produces pollen grains carrying the male germ cells. (ii) Ovary: the ovary of the pistil (carpel), which contains the ovules with the egg cells.

    Step-by-step solution →
19. Q199 CBSE 2024
    1. (a)​List any two contraceptive methods ​practised only by women. Mention how ​these ​methods work.
    2. (b)​Write the two roles ​performed ​by ​testes in human males.
    Show answer

    Oral pills stop release of eggs and blocked fallopian tubes stop the egg reaching the uterus; the testes make sperms and secrete testosterone.

    (a) (i) Oral contraceptive pills: they change the hormonal balance of the body so that eggs are not released, so fertilisation cannot occur. (ii) Surgical blocking of the fallopian tubes: the egg cannot reach the uterus, so fertilisation does not take place. A copper-T placed in the uterus, or a covering worn in the vagina that stops sperms reaching the egg, also earns credit. (b) The testes (i) produce sperms, the male germ cells, and (ii) secrete the male hormone testosterone, which regulates sperm formation and brings about the changes seen in boys at puberty.

    Step-by-step solution →
20. Q200 CBSE 2024
    (a) Name a part of ​the flower which

    1. (i)​persists even after a fruit is ​formed,
    2. (ii)attracts insects for pollination, ​
    3. (iii)produces pollen grains and
    4. (iv)changes ​into seed ​after fertilisation. (b) After pollination, ​how does a male germ cell reach the ovary ? Mention the significance of this ​event.
    Show answer

    Sepals, petals, anther and ovule; the pollen tube carries the male germ cell to the ovule, making fertilisation possible.

    (a) (i) Sepals (calyx); (ii) Petals (corolla); (iii) Anther (of the stamen); (iv) Ovule. (b) After the pollen grain lands on a suitable stigma, a pollen tube grows out of it and travels down through the style to the ovary, where it enters an ovule; the male germ cell moves down this tube and so reaches the female germ cell. Significance: it makes fertilisation possible. The male and female germ cells fuse to form the zygote, which develops into the embryo, and the ovule then becomes the seed and the ovary the fruit.

    Step-by-step solution →