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.

NCERT exercises

Exercises (11) Intext Questions (Page 114) (2) Intext Questions (Page 119) (5) Intext Questions (Page 126) (5)

NCERT Exemplar exercises

Multiple Choice Questions (27) Short Answer Questions (21) Long Answer Questions (10)

CBSE Class 10 Science previous year papers, with answers →

Questions · page 12 of 22

Q221 CBSE 2023
The organism in which an outgrowth on the parent body develops into a new individual is :
1. (a)Amoeba
2. (b)Paramecium
3. (c)Rhizopus
4. (d)Yeast
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(d) Yeast

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Q222 CBSE 2023
Plants which bear unisexual flowers are :
1. (a)Mustard and Papaya
2. (b)Hibiscus and Watermelon
3. (c)Mustard and Hibiscus
4. (d)Watermelon and Papaya
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(d) Watermelon and Papaya

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Q223 CBSE 2023
Choose the correct order of the stages of binary fission in Leishmania.
1. (a)I, II, III, IV, V
2. (b)I, III, II, V, IV
3. (c)I, III, V, II, IV
4. (d)I, II, III, V, IV
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(b) I, III, II, V, IV

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Q224 CBSE 2023
The thread like structures that develop on a moist slice of bread in Rhizopus are
1. (a)Sporangia
2. (b)Filaments
3. (c)Rhizoids
4. (d)Hyphae
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(d) Hyphae

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Q225 CBSE 2023
Select the INCORRECT match (between the plant and its vegetative part) from the following :
1. (a)Bryophyllum, leaf
2. (b)Potato, stem
3. (c)Money-plant, stem
4. (d)Rose, root
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(d) Rose, root

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Q226 CBSE 2023
The number of chromosomes in parents and offsprings of a particular species undergoing sexual reproduction remain constant due to :
1. (a)doubling of chromosomes after zygote formation.
2. (b)halving of chromosomes after zygote formation.
3. (c)doubling of chromosomes before gamete formation.
4. (d)halving of chromosomes at the time of gamete formation.
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(d) halving of chromosomes at the time of gamete formation.

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Q227 CBSE 2023
The bacterial and the viral infections that may be caused due to unsafe sex respectively are :
1. (a)Warts and HIV-AIDS
2. (b)HIV-AIDS and Warts
3. (c)Gonorrhoea and Syphilis
4. (d)Syphilis and Warts
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(d) Syphilis and Warts

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Q228 CBSE 2023
When an organism breaks into a number of parts and each part develops into a complete organism, it is known as :
1. (a)budding
2. (b)regeneration
3. (c)vegetative propagation
4. (d)spore formation
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(b) regeneration

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Q229 CBSE 2023
Select from the following, a disease which is not transmitted sexually :
1. (a)Gonorrhoea
2. (b)Tuberculosis
3. (c)HIV-AIDS
4. (d)Syphilis
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(b) Tuberculosis

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Q230 CBSE 2023
Consider the following three flowers namely X, Y and Z. Which flower(s) would develop into a fruit ?
1. (a)'X' only
2. (b)'Z' only
3. (c)'X' and 'Y' only
4. (d)'Y' and 'Z'
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(c) 'X' and 'Y' only

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Q231 CBSE 2023
Two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to this question from the codes (a), (b), (c) and (d) as given below.
Assertion (A): When a bacterium divides into two, and the resultant two bacteria divide again, the four bacteria produced would be almost similar.
Reason (R): DNA copying involves small inaccuracies in the reproduction process.
1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. (c)Assertion (A) is true, but Reason (R) is false.
4. (d)Assertion (A) is false, but Reason (R) is true.
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(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

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Q232 CBSE 2023
These consists of two statements – Assertion (A) and Reason (R). Answer this question selecting the appropriate option given below :
Assertion (A): Testes in human males are located outside the abdominal cavity in scrotum.
Reason (R): Scrotum provides a lower temperature than the normal body temperature for sperm formation.
1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of (A).
2. (b)Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of (A).
3. (c)Assertion (A) is true, but Reason (R) is false.
4. (d)Assertion (A) is false, but Reason (R) is true.
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(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of (A).

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Q233 CBSE 2023
Two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to this question from the codes (a), (b), (c) and (d) as given below.
Assertion (A): Variation is useful for the survival of a species over time.
Reason (R): The process of DNA copying will have variation each time because biochemical reactions are not reliable.
1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. (c)Assertion (A) is true, but Reason (R) is false.
4. (d)Assertion (A) is false, but Reason (R) is true.
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(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

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Q234 CBSE 2023

Name the glands which add their secretions to the sperms. List two function of these secretions.

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The seminal vesicles and prostate gland; their secretions nourish the sperms and give a fluid medium that makes transport easier.
The seminal vesicles and the prostate gland add their secretions to the sperms. Two functions of these secretions are: (i) They provide nutrition to the sperms, the fructose in them supplying the energy the sperms need to swim; (ii) They provide a fluid medium in which the sperms are suspended, so that the transport of the sperms becomes easier. The sperms together with these secretions are called semen.

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Q235 CBSE 2023

When leaves of ‘Bryophyllum’ fall on the soil they develop into new plants, but leaves of a lemon plant cannot do so. Why ? Name the method of reproduction by which these plants multiply.

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Bryophyllum leaves carry buds in their notches that grow into new plants, but lemon leaves have none; the method is vegetative propagation.
A Bryophyllum leaf carries buds in the notches along its margin. When the leaf falls on moist soil, these buds develop roots and shoots and grow into new plants. A lemon leaf carries no such buds on its margin, so there is no bud from which a new plant can grow, and it simply withers. The method is vegetative propagation, a form of asexual reproduction in which a new plant develops from a vegetative part of the parent, here the leaf. (Lemon plants are multiplied from seeds, or artificially by vegetative propagation using the stem, as in layering or grafting.)

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Q236 CBSE 2023
Identify one organ each in human
1. (i)male, and
2. (ii)female reproductive system which plays a role of endocrine gland along with the production of germ cells. Name a hormone secreted by each of them.
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Male: testes, secreting testosterone; female: ovaries, secreting oestrogen.
(i) Male: the testes. Besides producing the sperms (male germ cells), they act as endocrine glands and secrete the hormone testosterone. (ii) Female: the ovaries. Besides producing the eggs or ova (female germ cells), they act as endocrine glands and secrete the hormone oestrogen; progesterone, also secreted by the ovaries, equally answers "a hormone".

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Q237 CBSE 2023
(a) Mention the role of the following organs of human male reproductive system :
1. (i)Testis
2. (ii)Scrotum
3. (iii)Vas-deferens
4. (iv)Seminal vesicle (b) What is Placenta ? State its function in a human female.
Show answer

Testis makes sperms, scrotum keeps them cool, vas deferens carries them, seminal vesicle nourishes them; the placenta passes food and oxygen to the embryo.
(a)(i) Testis: forms the male germ cells (sperms) and secretes the hormone testosterone, which regulates the formation of sperms and brings about the changes seen in boys at puberty. (ii) Scrotum: holds the testes outside the abdominal cavity, because sperm formation requires a temperature lower than the normal body temperature. (iii) Vas deferens: delivers the sperms from the testis; it unites with the tube from the urinary bladder, so the urethra is a common passage for sperms and urine. (iv) Seminal vesicle: adds its secretion (with that of the prostate gland) to the sperms; this fluid makes their transport easier and provides nutrition. (b) The placenta is a special tissue, a disc embedded in the uterine wall, that connects the embryo to the mother. It has villi on the embryo's side surrounded by blood spaces on the mother's side, giving a large surface area through which glucose and oxygen pass from the mother's blood to the embryo, and through which the embryo's wastes pass into the mother's blood to be removed.

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Q238 CBSE 2023
1. (a)Name the parts of a bisexual flower that are not directly involved in reproduction.
2. (b)Differentiate between self pollination and cross pollination. List any two significance of pollination.
3. (c)What is the fate of ovules and ovary after fertilization in a flower ?
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Sepals and petals are not directly involved in reproduction; self and cross pollination differ; the ovule becomes the seed and the ovary the fruit.
(a) The sepals (calyx) and the petals (corolla). They form the accessory whorls: the sepals protect the flower in the bud and the petals attract pollinators, but neither produces a gamete. (b) In self pollination the pollen of a flower falls on the stigma of the same flower, or of another flower of the same plant; only one parent is involved, no external agent is needed when the pollen falls on the stigma of the same flower, and the offspring show almost no variation. In cross pollination the pollen is carried to the stigma of a flower on a different plant of the same species; two parents are involved, an agent such as wind, water or an insect is needed and the offspring show variation. Two significances of pollination: (1) it brings the male gamete to the female part of the flower, so that fertilization and the formation of seeds and fruits can take place; (2) cross pollination introduces variation, which makes the species healthier and better able to adapt. (c) After fertilization each ovule develops into a seed, the zygote inside it growing into the embryo, and the ovary develops into the fruit. The sepals, petals, stamens, style and stigma usually wither and fall off.

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Q239 CBSE 2023
1. (i)Name and explain the two modes of asexual reproduction observed in hydra.
2. (ii)What is vegetative propagation ? List two advantages of using this technique.
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Hydra reproduces by budding and regeneration; vegetative propagation raises plants from vegetative parts, giving earlier flowering and multiplying seedless plants.
(i) The two modes are budding and regeneration. In budding, repeated cell division at one particular site of the parent's body raises an outgrowth called a bud; the bud grows, develops its own tentacles, and on maturing detaches from the parent and lives as an independent hydra. In regeneration, a hydra cut into pieces gives a complete new hydra from each piece: specialised cells in the piece proliferate into a large mass of cells, and these then differentiate in an organised sequence into the various cell types and tissues of a whole body. (ii) Vegetative propagation is the asexual reproduction of plants in which new plants are raised from a vegetative part of the parent -- a root, stem, leaf or bud -- without gametes and without seeds. Two advantages: such plants bear flowers and fruits earlier than plants grown from seeds; and plants that have lost the capacity to form seeds, such as banana, orange, rose and jasmine, can still be multiplied. (Plants so raised are also genetically similar enough to the parent to have all its characteristics, so a desirable character is preserved.)

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Q240 CBSE 2023
Give reason for the following :
1. (a)During reproduction inheritance of different proteins will lead to altered body designs.
2. (b)Fertilization cannot take place in flowers if pollination does not occur.
3. (c)All multicellular organisms cannot give rise to new individuals through fragmentation or regeneration.
4. (d)Vegetative propagation is practised for growing only some type of plants.
5. (e)The parents and off-springs of organisms reproducing sexually have the same number of chromosomes.
Show answer

Inherited DNA decides proteins; pollen tubes need pollination; specialised bodies cannot regenerate; vegetative propagation suits some plants; meiosis halves chromosomes and fertilisation restores them.
(a) The body is built and run by proteins, and the DNA inherited from the parents decides which proteins are made; if different proteins are inherited, different structures and enzymes are built, so the body design is altered. (b) Pollination puts pollen on the stigma, and only then can the grain germinate and grow a pollen tube down the style to the ovule. That tube is the only route by which the male gamete reaches the egg, and fertilisation **is** their fusion — so without pollination it cannot happen. (c) Fragmentation and regeneration need a simple body made of relatively unspecialised cells. Most multicellular organisms have highly specialised cells organised into tissues and organ systems, and a loose fragment cannot rebuild all of them, so they cannot produce a new individual this way. (d) It is used for plants that have lost the ability to produce viable seeds (banana, orange, rose, jasmine) and for varieties worth copying exactly, since the new plants are genetically identical to the parent and flower and fruit earlier. It also needs a plant whose root, stem or leaf can grow into a new plant (sugarcane, rose and grape by cuttings or layering, potato by its tubers, Bryophyllum by leaf buds), so only some types of plant are raised this way. (e) Gametes are made by meiosis, which halves the chromosome number ( $2 n \to n$ , in humans $46 \to 23$ ). At fertilisation two gametes fuse, so the zygote gets $23 + 23 = 46$ again — the same number as each parent.

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