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 21 of 22

Q401 CBSE 2017
Write the functions of the following parts of human female reproductive system :
1. (i)Ovary ;
2. (ii)Fallopian tubes ;
3. (iii)Uterus
Show answer

The ovary produces eggs, the fallopian tubes carry the egg where fertilisation occurs, and the uterus holds the developing embryo until birth.
(i) Ovary: produces the female germ cells, the eggs (ova); after puberty, one egg is released every month by one of the two ovaries. The ovaries also produce female hormones, such as oestrogen. (ii) Fallopian tubes (oviducts): carry the egg from the ovary towards the uterus; the sperms meet the egg in the fallopian tube, so fertilisation takes place here. (iii) Uterus: the fertilised egg (zygote) is implanted in its thick, blood-rich lining, and the embryo develops there until birth, nourished from the mother’s blood through the placenta.

Step-by-step solution →
Q402 CBSE 2017
1. (a)Why does menstruation occur ?
2. (b)List in tabular form two distinguishing features between a sperm and an ovum.
Show answer

Menstruation sheds the uterine lining when the egg is not fertilised; a sperm is small and motile, an ovum large and non-motile.
(a) Every month an ovary releases an egg, and the uterus prepares to receive a fertilised egg: its lining becomes thick and spongy and richly supplied with blood, to nourish an embryo. If the egg is not fertilised, this lining is not needed. It slowly breaks down and comes out through the vagina as blood and mucus. This monthly flow is menstruation; it usually lasts about 2 to 8 days. (b) Sperm and ovum compared: (1) Size: the sperm is very small; the ovum is much larger. (2) Movement: the sperm is motile and swims with its tail; the ovum is not motile and has no tail. Other differences: the ovum stores food for the early embryo while the sperm has very little, and sperms are made in the testes while ova are made in the ovaries.

Step-by-step solution →
Q403 CBSE 2017

What is placenta ? Describe its two major functions.

Show answer

The placenta connects the embryo to the mother; it passes food and oxygen to the embryo and removes its wastes.
Placenta: a special disc-shaped tissue embedded in the wall of the uterus that connects the developing embryo to the mother. It has villi on the embryo's side, surrounded by blood spaces on the mother's side, and the embryo is joined to it by the umbilical cord. Two major functions: (i) Supplying food and oxygen: glucose and oxygen pass from the mother's blood into the embryo's blood across the large surface provided by the villi, giving the embryo its nutrition. (ii) Removing wastes: waste substances produced by the embryo, such as carbon dioxide, pass from the embryo's blood into the mother's blood and are removed by her body.

Step-by-step solution →
Q404 CBSE 2017

Name the three parts A, B and C of the flower shown in the figure and state one function of each.

Show answer

A is the anther (makes pollen), B the style (path of the pollen tube), C the ovary (holds ovules, becomes the fruit).
A: Anther. It produces the pollen grains, which carry the male germ-cells. B: Style. After pollination, the pollen tube grows down through the style from the stigma to reach the ovary. C: Ovary. It contains the ovules, each with an egg cell (the female germ-cell); after fertilisation the ovary develops into the fruit.

Step-by-step solution →
Q405 CBSE 2017
The teacher explained in the class that reproduction is the process by which organisms increase their population. Manoj wanted to know more about the reproductive-health. Therefore, the teacher also explained in the class about the diseases that can be transmitted, if proper care is not taken.
1. (i)Why is the increasing human population a cause of concern for all of us ?
2. (ii)Name two diseases that can be sexually transmitted.
3. (iii)State one value each displayed by Manoj and his teacher.
Show answer

A growing population strains limited resources; gonorrhoea and syphilis are sexually transmitted; Manoj shows curiosity and the teacher shows responsibility.
(i) The resources on which we all depend, such as land, food, water, fuel, housing and jobs, are limited. An ever-increasing population puts more and more pressure on them, leading to shortages, overcrowding, unemployment and pollution, and it makes it harder to improve everybody's standard of living. (ii) Gonorrhoea and syphilis (both bacterial). Warts and HIV-AIDS (viral) are other examples. (iii) Manoj: curiosity, an eagerness to learn about and be aware of matters of health. The teacher: a sense of responsibility and care for the students' health and well-being, spreading awareness about reproductive health.

Step-by-step solution →
Q406 CBSE 2017

What is asexual reproduction ? Write the process of budding in Hydra.

Show answer

One parent forms new individuals without gametes; in Hydra a bud grows, develops a mouth and tentacles, then detaches as a new Hydra.
Asexual reproduction is the mode of reproduction in which a single parent produces new individuals without the formation and fusion of gametes; the offspring are very similar to the parent. Budding in Hydra: Hydra uses its regenerative cells for reproduction. (1) At one specific site on the body, cells divide repeatedly and form an outgrowth called a bud. (2) The bud grows and develops a mouth and tentacles, becoming a tiny Hydra while still attached to the parent. (3) When fully mature, it detaches from the parent body and becomes a new, independent Hydra.

Step-by-step solution →
Q407 CBSE 2017

What is DNA copying ? State its importance.

Show answer

DNA copying builds a second copy of a cell's DNA; it passes on body design, and its small inaccuracies give variation.
DNA copying: the DNA in the nucleus of a cell is the information source for making proteins. When a cell reproduces, it uses chemical reactions to build a copy of its DNA, so that two copies are formed. This is accompanied by the making of additional cellular apparatus, and the two DNA copies then separate, each with its own cellular apparatus, as the cell divides into two. This is DNA copying. Importance: 1. It is the basic event in reproduction: it passes on the information for making proteins, and so the body design, from parent to offspring. Consistent copying maintains the body-design features that suit the organism to its niche, which keeps populations of the species stable. 2. Copying is not absolutely accurate, so small variations arise in the copies. These variations are the basis of evolution and help a species survive when its niche changes, since some variants may survive conditions that kill the rest.

Step-by-step solution →
Q408 CBSE 2017

List and explain briefly any three methods of contraception.

Show answer

Barrier methods block sperms, oral pills stop release of eggs, and surgical methods block the sperm ducts or fallopian tubes.
Any three of the following: (1) Barrier (mechanical) method: a condom on the penis, or a similar covering worn in the vagina, prevents the sperms from reaching the egg; condoms also help to prevent sexually transmitted infections. (2) Hormonal (chemical) method: oral pills change the hormonal balance of the body so that eggs are not released, and fertilisation cannot occur (the pills may have side effects). (3) Surgical method: blocking the vas deferens in the male (vasectomy) prevents the transfer of sperms, and blocking the fallopian tubes in the female (tubectomy) prevents the egg from reaching the uterus; in both cases fertilisation does not take place. (4) Intra-uterine device: a loop or copper-T placed in the uterus prevents pregnancy (it may cause side effects by irritating the uterus).

Step-by-step solution →
Q409 CBSE 2017
1. (a)Identify ‘A’, ‘B’, ‘C’ and ‘D’ in the given diagram.
2. (b)What is meant by pollination ? Explain its significance.
3. (c)Explain the process of fertilization in flowers. Name the parts of the flower that develop after fertilization into (i) seeds, (ii) fruits.
Show answer

A is the pollen grain, B the pollen tube, C the ovary and D the egg; ovules become seeds and the ovary the fruit.
(a) A: pollen grain (germinating on the stigma); B: pollen tube; C: ovary; D: female germ-cell (egg) inside the ovule. (b) Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a flower; within the same flower it is self-pollination, and from one flower to another it is cross-pollination. Significance: it brings the male germ-cells to the female part of the flower, so that fertilisation, and then the formation of seeds and fruit, can take place; cross-pollination between flowers of different plants also brings together germ-cells from two parents and so gives variation among the offspring. (c) A pollen grain on a suitable stigma grows a pollen tube, which passes through the style and reaches the ovule in the ovary. The male germ-cell travels down the tube and fuses with the female germ-cell (egg) inside the ovule; this is fertilisation, and it forms a zygote, which divides to form the embryo. After fertilisation (i) the ovules develop into seeds and (ii) the ovary develops into the fruit.

Step-by-step solution →
Q410 CBSE 2017
1. (a)Name the organ that produces sperms as well as secretes a hormone in human males. Name the hormone it secretes and write its functions.
2. (b)Name the parts of the human female reproductive system where fertilisation occurs.
3. (c)Explain how the developing embryo gets nourishment inside the mother’s body.
Show answer

Testes produce sperms and testosterone; fertilisation occurs in the oviducts; the embryo is nourished by the mother's blood through the placenta.
(a) The testes (singular testis) produce sperms and also secrete a hormone. The hormone is testosterone. Its functions: it regulates the formation of sperms, and it brings about the changes in appearance seen in boys at puberty (such as the growth of facial and body hair and the deepening of the voice). (b) Fertilisation occurs in the oviducts (fallopian tubes): the egg released by an ovary passes into an oviduct, the sperms travel up through the uterus into the oviduct, and they meet there. (c) After fertilisation the zygote is implanted in the thick, blood-rich lining of the uterus and develops into an embryo. It gets nutrition from the mother's blood through a special tissue, the placenta, a disc embedded in the uterine wall and joined to the embryo by the umbilical cord. The placenta has villi on the embryo's side, and on the mother's side there are blood spaces surrounding the villi. The villi provide a large surface area, so glucose and oxygen pass from the mother's blood to the embryo, and the wastes produced by the embryo pass into the mother's blood to be removed.

Step-by-step solution →
Q411 CBSE 2017

Give one example each of unisexual and bisexual flowers. Differentiate between the two types of pollination that occur in flowers. What happens when a pollen lands on a suitable stigma ? Write about the events that occur till the seed formation in the ovary.

Show answer

Self-pollination stays in one flower, cross-pollination goes between flowers; the pollen tube leads to fertilisation, then the ovule becomes the seed.
Unisexual flower: papaya (or watermelon). Bisexual flower: Hibiscus (or mustard). Self-pollination is the transfer of pollen from the anther to the stigma of the same flower; it usually needs no outside agent, and since the germ-cells come from one plant the offspring are usually similar to the parent. Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower, usually on another plant of the same species; it needs an agent such as wind, water, insects or birds, and when the pollen comes from another plant it combines germ-cells of different plants and gives more variation. When a pollen grain lands on a suitable stigma it germinates: a pollen tube grows out of it and travels through the style to reach the ovule in the ovary, carrying the male germ-cell. The male germ-cell fuses with the female germ-cell (egg) in the ovule: this is fertilisation, and it forms a zygote. The zygote divides several times to form an embryo within the ovule; the ovule develops a tough coat and is gradually converted into a seed; the ovary grows rapidly and ripens to form a fruit; and the petals, sepals, stamens, style and stigma may shrivel and fall off.

Step-by-step solution →
Q412 CBSE 2017
(a) Write the functions of each of the following parts in a human female reproductive system :
1. (i)Ovary
2. (ii)Uterus
3. (iii)Fallopian tube (b) Write the structure and functions of placenta in a human female.
Show answer

Ovary makes eggs, fallopian tube is the site of fertilisation, uterus holds the embryo; the placenta passes food and oxygen in and wastes out.
(a) (i) Ovary: produces the female germ cells, the eggs (one egg is produced every month by one of the ovaries), and female hormones. (ii) Uterus: the embryo is implanted in its thickened lining and develops there, nourished through the placenta, until birth; the rhythmic contraction of its muscles pushes the baby out at birth. (iii) Fallopian tube: carries the egg from the ovary towards the uterus; fertilisation takes place in it. (b) Structure: the placenta is a disc-shaped tissue embedded in the wall of the uterus. On the embryo's side it has finger-like villi, and on the mother's side blood spaces surround the villi, giving a large surface area. Functions: glucose (nutrition) and oxygen pass from the mother's blood to the embryo, and the waste substances of the embryo pass into the mother's blood to be removed.

Step-by-step solution →
Q413 CBSE 2017
(a) Write the functions of the following parts in human female reproductive system :
1. (i)Ovary
2. (ii)Uterus
3. (iii)Oviduct (b) How does the embryo get its nourishment inside the mother’s body ? Describe in brief.
Show answer

The ovary makes eggs and hormones, the oviduct hosts fertilisation, the uterus holds the embryo, and the placenta passes nutrients and wastes.
(a) (i) Ovary: produces the female gametes, the eggs (each month one egg is released by one of the ovaries), and secretes female hormones such as oestrogen. (ii) Uterus: the fertilised egg is implanted in its thickened, blood-rich lining, and the embryo develops there, nourished through the placenta, until birth; its muscles contract rhythmically to push the baby out at birth. (iii) Oviduct (fallopian tube): carries the egg from the ovary towards the uterus; fertilisation takes place in it. (b) The embryo is nourished through the placenta, a disc-like tissue embedded in the wall of the uterus. The placenta has villi on the embryo's side, surrounded by blood spaces on the mother's side, which give a large surface area. Glucose and oxygen pass from the mother's blood into the villi and reach the embryo through the umbilical cord, and the embryo's wastes pass into the mother's blood to be removed.

Step-by-step solution →
Q414 CBSE 2017

Draw a diagram of longitudinal section of a bisexual flower and label the following : Ovary, anther, style, stigma, filament Identify from these the female reproductive organs and state one function of each.

Show answer

The female organs are the stigma, which receives pollen, the style, through which the pollen tube grows, and the ovary, which holds the ovules.
Diagram: the longitudinal section of a bisexual flower, with the ovary, anther, style, stigma and filament labelled (see the figure). The anther and filament form the stamen, the male part. Female reproductive organs: the stigma, the style and the ovary, which together make up the pistil (carpel). Stigma: receives the pollen grains during pollination; its surface is often sticky. Style: joins the stigma to the ovary; the pollen tube grows down through it to carry the male germ-cell to the ovule. Ovary: contains the ovules, each with a female germ-cell (egg); after fertilisation the ovules become seeds and the ovary develops into the fruit.

Step-by-step solution →
Q415 CBSE 2017

Draw neat diagram of human female reproductive system. Label oviduct and uterus on it. State the role of placenta. How the waste generated by the developing embryo removed ?

Show answer

The placenta passes glucose and oxygen from the mother's blood to the embryo, and the embryo's wastes pass into the mother's blood.
Diagram: a front view of the human female reproductive system shows two ovaries, one on each side; an oviduct (fallopian tube) running from near each ovary to the upper part of the uterus; the uterus, a hollow pear-shaped organ in the middle; the cervix, the narrow neck of the uterus; and the vagina below it. The oviduct and the uterus are labelled (see the figure). Role of the placenta: the placenta is a special disc-like tissue embedded in the uterine wall. It has villi on the embryo’s side, surrounded by blood spaces on the mother’s side, which give a large surface area for glucose and oxygen to pass from the mother’s blood to the embryo. The embryo thus gets its nutrition from the mother’s blood through the placenta. Removal of wastes: the waste substances generated by the developing embryo are removed by transferring them into the mother’s blood through the placenta.

Step-by-step solution →
Q416 CBSE 2017
(a) Write the functions of the following parts in human female reproductive system :
1. (i)Ovary
2. (ii)Fallopian tube
3. (iii)Uterus (b) Describe the structure and functions of placenta.
Show answer

The ovary makes eggs, the Fallopian tube hosts fertilisation, the uterus holds the embryo, and the placenta exchanges nutrients and wastes.
(a) (i) Ovary: it produces the female germ-cells (eggs); one egg is released every month by one of the ovaries. The ovaries also produce female hormones such as oestrogen. (ii) Fallopian tube (oviduct): it carries the egg from the ovary towards the uterus, and it is the site of fertilisation, where a sperm meets the egg. (iii) Uterus: the fertilised egg (zygote) gets implanted in its thick, blood-rich lining and develops there into the embryo and then the foetus, which is nourished through the placenta; at birth, rhythmic contractions of the muscles of the uterus push the baby out. (b) Structure: the placenta is a special disc-like tissue embedded in the uterine wall. On the embryo's side it has finger-like projections called villi; on the mother's side are blood spaces that surround the villi, so that a large surface area is available for exchange. The embryo is joined to it by the umbilical cord. Functions: glucose (food) and oxygen pass from the mother's blood to the embryo across the villi, and the wastes produced by the embryo, such as carbon dioxide, pass into the mother's blood to be removed. The two blood streams do not normally mix.

Step-by-step solution →
Q417 CBSE 2017
(a) What is pollination ? Give its two types. (b) Draw a longitudinal section of female reproductive part of a flower showing germination of pollen grain. Label on it the following :
1. (i)Stigma ;
2. (ii)Pollen tube with a male germ cell ;
3. (iii)Female germ cell.
Show answer

Pollination is of two types, self and cross; the pollen tube carries the male germ cell down the style to the ovule.
(a) Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a carpel. Its two types are (1) self-pollination, in which the pollen reaches the stigma of the same flower, and (2) cross-pollination, in which the pollen is carried from one flower to the stigma of another flower of the same species, usually on a different plant, by agents such as wind, water or animals. (b) The diagram shows the pistil in longitudinal section with pollen grains on the stigma. From one grain a pollen tube grows down through the style into the ovary and enters an ovule. Labelled: (i) stigma, at the top of the pistil; (ii) pollen tube, with a male germ cell inside it near its tip; (iii) female germ cell (egg), inside the ovule.

Step-by-step solution →
Q418 CBSE 2017
A student observes the following stage of binary fission in Amoeba in a focussed slide under a microscope. Select the correct observation in this regard.
1. (a)First stage of binary fission
2. (b)Final stage of binary fission
3. (c)That stage of binary fission in which the cytoplasm divides but the nucleus does not
4. (d)That stage of binary fission in which the nucleus divides but the cytoplasm does not
Show answer

(d) That stage of binary fission in which the nucleus divides but the cytoplasm does not

Step-by-step solution →
Q419 CBSE 2017
A student while observing an embryo of a gram seed listed various parts of the embryo as listed below : Testa, Micropyle, Cotyledon, Tegmen, Plumule, Radicle. On examining the list the teacher commented that only three parts are correct. Select these three correct parts :
1. (a)Cotyledon, Testa, Plumule
2. (b)Cotyledon, Plumule, Radicle
3. (c)Cotyledon, Tegmen, Radicle
4. (d)Cotyledon, Micropyle, Plumule
Show answer

(b) Cotyledon, Plumule, Radicle

Step-by-step solution →
Q420 CBSE 2017
Choose the correct statement(s) on budding in yeast from the following : I. A parent cell divides into two or more daughter cells and here the parent identity is lost. II. In this the elongated nucleus divides to form two or more daughter nuclei. III. A bud arises from a particular region on a parent body. IV. After detaching from the parent body the bud grows into a new independent individual.
1. (a)I only
2. (b)III only
3. (c)II and III only
4. (d)III and IV only
Show answer

(d) III and IV only

Step-by-step solution →