Class 10 Science · Chapter 8

Heredity

120 Class 10 Science questions on Heredity from the NCERT textbook, NCERT Exemplar and CBSE board papers 2024–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 2 of 6

1. Q21 Exemplar · Multiple Choice Questions
   Two pea plants ​one with round ​green seeds (RRyy) ​and another with wrinkled yellow (rrYY) seeds produce $F_1$ progeny that have round, yellow ​(RrYy) seeds. When $F_1$ plants are selfed, ​the $F_2$ progeny will have ​new combination of characters. Choose the new ​combination from the following

   1. (i)Round, yellow
   2. (ii)Round, green
   3. (iii)Wrinkled, yellow
   4. (iv)Wrinkled, ​green

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

   (b) (i) and (iv)

   Step-by-step solution →
2. Q22 Exemplar · Multiple Choice Questions
   A ​basket of vegetables contains carrot, potato, ​radish and tomato. Which ​of ​them ​represent the correct homologous ​structures?

   1. (a)Carrot and potato
   2. (b)Carrot and tomato
   3. (c)Radish and carrot
   4. (d)Radish and potato
   Show answer

   (c) Radish and carrot

   Step-by-step solution →
3. Q23 Exemplar · Multiple Choice Questions
   Select the correct statement

   1. (a)Tendril of a pea plant and phylloclade of Opuntia are homologous
   2. (b)Tendril of a pea plant and phylloclade of Opuntia are analogous
   3. (c)Wings of birds and limbs of lizards are analogous
   4. (d)Wings of birds and wings of bat are homologous
   Show answer

   (a) Tendril of a pea plant and phylloclade of Opuntia are homologous

   Step-by-step solution →
4. Q24 Exemplar · Multiple Choice Questions
   If ​the fossil ​of an organism ​is ​found in the ​deeper layers ​of ​earth, then we can predict that

   1. (a)the extinction of organism has occurred recently
   2. (b)the extinction of organism has occurred thousands of years ago
   3. (c)the fossil position in the layers of earth is not related to its time of extinction
   4. (d)time of extinction cannot be determined
   Show answer

   (b) the extinction of organism has occurred thousands of years ago

   Step-by-step solution →
5. Q25 Exemplar · Multiple Choice Questions
   Which of ​the following statements ​is not ​true with ​respect ​to variation?

   1. (a)All variations in a species have equal chance of survival
   2. (b)Change in genetic composition results in variation
   3. (c)Selection of variants by environmental factors forms the basis of evolutionary processes.
   4. (d)Variation is minimum in asexual reproduction
   Show answer

   (a) All variations in a species have equal chance of survival

   Step-by-step solution →
6. Q26 Exemplar · Multiple Choice Questions
   A trait in ​an ​organism ​is influenced ​by

   1. (a)paternal DNA only
   2. (b)maternal DNA only
   3. (c)both maternal and paternal DNA
   4. (d)neither by paternal nor by maternal DNA
   Show answer

   (c) both maternal and paternal DNA

   Step-by-step solution →
7. Q27 Exemplar · Multiple Choice Questions
   Select ​the group which ​shares ​maximum number ​of ​common ​characters

   1. (a)two individuals of a species
   2. (b)two species of a genus
   3. (c)two genera of a family
   4. (d)two genera of two families
   Show answer

   (a) two individuals of a species

   Step-by-step solution →
8. Q28 Exemplar · Multiple Choice Questions
   According ​to ​the evolutionary ​theory, ​formation of a ​new ​species is generally ​due to

   1. (a)sudden creation by nature
   2. (b)accumulation of variations over several generations
   3. (c)clones formed during asexual reproduction
   4. (d)movement of individuals from one habitat to another
   Show answer

   (b) accumulation of variations over several generations

   Step-by-step solution →
9. Q29 Exemplar · Multiple Choice Questions
   From the list ​given ​below, ​select ​the ​character which can be acquired ​but ​not inherited

   1. (a)colour of eye
   2. (b)colour of skin
   3. (c)size of body
   4. (d)nature of hair
   Show answer

   (c) size of body

   Step-by-step solution →
10. Q30 Exemplar · Multiple Choice Questions
    The two versions of a ​trait ​(character) ​which ​are ​brought in by the male and female ​gametes ​are situated on

    1. (a)copies of the same chromosome
    2. (b)two different chromosomes
    3. (c)sex chromosomes
    4. (d)any chromosome
    Show answer

    (a) copies of the same chromosome

    Step-by-step solution →
11. Q31 Exemplar · Multiple Choice Questions
    Select the statements that describe characteristics of genes

    1. (i)genes are ​specific sequence of ​bases in a DNA molecule
    2. (ii)a ​gene does not ​code for proteins
    3. (iii)in individuals of ​a given species, a specific gene is located on ​a particular ​chromosome
    4. (iv)each chromosome ​has only one gene

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

    (b) (i) and (iii)

    Step-by-step solution →
12. Q32 Exemplar · Multiple Choice Questions
    In ​peas, a pure ​tall plant ​(TT) is crossed with ​a ​short plant (tt). The ratio of ​pure ​tall plants to short plants in $F_2$ is

    1. (a)1 : 3
    2. (b)3 : 1
    3. (c)1 : 1
    4. (d)2 : 1
    Show answer

    (c) 1 : 1

    Step-by-step solution →
13. Q33 Exemplar · Multiple Choice Questions
    The number ​of ​pair (s) ​of ​sex chromosomes in ​the zygote of ​humans ​is

    1. (a)one
    2. (b)two
    3. (c)three
    4. (d)four
    Show answer

    (a) one

    Step-by-step solution →
14. Q34 Exemplar · Multiple Choice Questions
    The theory ​of ​evolution ​of ​species by natural ​selection was given ​by

    1. (a)Mendel
    2. (b)Darwin
    3. (c)Morgan
    4. (d)Lamarck
    Show answer

    (b) Darwin

    Step-by-step solution →
15. Q35 Exemplar · Multiple Choice Questions
    Some dinosaurs ​had feathers ​although ​they ​could not fly but birds ​have feathers that help them ​to ​fly. In the context ​of evolution this means that

    1. (a)reptiles have evolved from birds
    2. (b)there is no evolutionary connection between reptiles and birds
    3. (c)feathers are homologous structures in both the organisms
    4. (d)birds have evolved from reptiles
    Show answer

    (d) birds have evolved from reptiles

    Step-by-step solution →
16. Q36 Exemplar · Short Answer Questions
    How ​is the sex ​of ​a ​newborn ​determined in humans?
    Show answer

    The sperm decides: an $\text{X}$ sperm gives a girl ($\text{XX}$), a $\text{Y}$ sperm a boy ($\text{XY}$), each with a $50:50$ chance.

    The sex is fixed at fertilisation by the sex chromosome carried in the sperm. A woman is $\text{XX}$ and makes only $\text{X}$ eggs; a man is $\text{XY}$ and makes $\text{X}$ and $\text{Y}$ sperms in equal numbers. An $\text{X}$ sperm gives an $\text{XX}$ zygote, which develops into a girl, and a $\text{Y}$ sperm gives an $\text{XY}$ zygote, which develops into a boy. The father's gamete therefore determines the sex of the newborn, with a $50:50$ chance either way.

    Step-by-step solution →
17. Q37 Exemplar · Short Answer Questions
    Do ​genetic combination ​of mothers ​play a significant role in ​determining the sex of ​a ​new ​born?
    Show answer

    No: every egg carries an $\text{X}$ whatever the mother's genotype, so the father's sperm ($\text{X}$ or $\text{Y}$) decides the sex.

    No. The genetic combination of the mother plays no significant role. A human female is $\text{XX}$, so both members of her sex-chromosome pair are alike and every egg she makes carries an $\text{X}$ chromosome, whatever the rest of her genotype. The father is $\text{XY}$ and makes $\text{X}$ and $\text{Y}$ sperms in equal numbers. The zygote becomes $\text{XX}$ (girl) or $\text{XY}$ (boy) according to which sperm fertilises the egg, so the sex of the newborn is decided by the father's gamete and by chance, not by the mother.

    Step-by-step solution →
18. Q38 Exemplar · Short Answer Questions
    Mention ​three important features ​of fossils ​which ​help ​in ​the ​study of evolution.
    Show answer

    Position in the earth's layers gives their order, radioactive dating gives their age, and preserved body design allows comparison with living forms.

    (i) Position in the earth's layers: fossils in the deeper layers are older than those nearer the surface, so the order in which different organisms lived can be read from the strata. (ii) Measurable age: the age of a fossil is found by dating the fossil or its surrounding rock from the decay of radioactive elements, for example carbon dating, so the timing of evolutionary change can be fixed. (iii) Preserved body design: a fossil keeps the structure of an organism that is now extinct, so it can be compared with living forms, and connecting links such as Archaeopteryx, which has feathers and wings of a bird together with the teeth and tail of a reptile, show that one group has arisen from another.

    Step-by-step solution →
19. Q39 Exemplar · Short Answer Questions
    Why ​do all ​the ​gametes ​formed ​in ​human females have ​an X chromosome?
    Show answer

    A human female is $\text{XX}$, and meiosis separates the pair, so every egg receives one $\text{X}$ chromosome.

    Because the sex-chromosome pair of a human female is $\text{XX}$, that is, both of its members are $\text{X}$ chromosomes. During meiosis the two members of every pair separate and each gamete receives exactly one of them, so an egg must receive an $\text{X}$; a female has no other kind of sex chromosome to pass on. The female is therefore the homogametic sex, producing only one kind of gamete, unlike the male, whose $\text{XY}$ pair yields $\text{X}$ and $\text{Y}$ sperms in equal numbers.

    Step-by-step solution →
20. Q40 Exemplar · Short Answer Questions
    In human ​beings, the statistical probability of ​getting either ​a ​male or female child ​is 50 : 50. ​Give a suitable explanation.
    Show answer

    Every egg carries $\text{X}$ while half the sperms carry $\text{X}$ and half $\text{Y}$, so girls and boys are equally likely, $50:50$.

    The mother is $\text{XX}$ and gives an $\text{X}$ chromosome to every egg, so her contribution is the same each time. The father is $\text{XY}$, and every meiotic division separates that pair, so he produces $\text{X}$-bearing and $\text{Y}$-bearing sperms in equal numbers. Fertilisation is random, so an $\text{X}$ sperm and a $\text{Y}$ sperm have the same chance of reaching the egg. Half the zygotes are therefore $\text{XX}$, which develop into girls, and half are $\text{XY}$, which develop into boys, giving $P(\text{girl})=P(\text{boy})=\frac{1}{2}$, that is $50:50$. Being a statistical probability it holds over a large number of births; an individual family may still have children of only one sex.

    Step-by-step solution →