NCERT Exemplar Class 10 Science Solutions Chapter 8 How do Organisms Reproduce

NCERT Exemplar Class 10 Science Solutions Chapter 8 How do Organisms Reproduce is a great study material for 10th standard students as it gives easy and simple answers to the questions in textbooks. The answers in the chapter not only help in obtaining board exam success but also give a sound foundation to competitive exams like NEET. These solutions are a supply of brief explanations of key concepts such as DNA replication, modes of reproduction, and reproductive health given in the NCERT Class 10 Science Book.

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This Story also Contains

1. Detailed Answers to the NCERT Exemplar for Class 10 Science Chapter 8– How Do Organisms Reproduce?
2. Access Answers to Chapter 8 NCERT Exemplar Class 10 Science (Short Answer)
3. Find Answers to Class 10 Science NCERT Exemplar Chapter 8(Long Answer)
4. Overview of Chapter 8 for Class 10 Science
5. Important diagrams in Class 10 Science Chapter 8
6. NCERT Class 10 Science Exemplar Solutions for Other Chapters:
7. NCERT Class 10 Science Exemplar Solutions Chapter 8- Types of Questions and Their Weightage in Board Exams
8. Topics Covered in NCERT Exemplar Class 10 Science Solutions Chapter 8:
9. CBSE NCERT Solutions for Class 10 Science - Chapter-wise

These Exemplar solutions are as per the CBSE 10 Syllabus 2025-26 and include different kinds of questions, i.e., 27 MCQs, 21 SAQs, and 11 LAQs. These questions will help students to practice all kinds of questions on the subject of reproduction in organisms. By solving these problems, students will be able to improve their understanding of key topics and enhance their skills to secure high marks in their exams.

Detailed Answers to the NCERT Exemplar for Class 10 Science Chapter 8– How Do Organisms Reproduce?

The detailed answers to the solutions are given below:

Question:1

In the list of organisms given below, those that reproduce by the asexual method are
(i) banana
(ii) dog
(iii) yeast
(iv) Amoeba
(a) (ii) and (iv)
(b) (i), (iii) and (iv)
(c) (i) and (iv)
(d) (ii), (iii) and (iv)

Answer: B

Solution: Bananas do not have seeds. They reproduce asexually by vegetative propagation. Yeast reproduces asexually by budding and amoeba by binary fission, multiple fission, sporulation and regeneration. Only the dog reproduces by the sexual method of reproduction.

Question:2

In a flower, the parts that produce male and female gametes (germ cells) are-
(a) stamen and anther
(b) filament and stigma
(c) anther and ovary
(d) stamen and style

Answer: C

Solution: Stamen is the male reproductive part of the flower, and it consists of 2 parts-anther and filament. The anther is the topmost part of the flower that produces male gametes-pollen grains. The carpel is the female reproductive part of the flower. It consists of stigma, style and ovary. The ovary is present at the base of the carpel and contains ovules- the female gametes.

Question:3

Which of the following is the correct sequence of events of sexual reproduction in a flower?
(a) pollination, fertilization, seedling, embryo
(b) seedling, embryo, fertilization, pollination
(c) pollination, fertilization, embryo, seedling
(d) embryo, seedling, pollination, fertilization

Answer: C

Solution: The correct sequence of events of sexual reproduction in flowers is:

Pollination, fertilization, embryo, seedling

(1) Pollination- the transfer of pollen grains to the stigma.

(2) Fertilization- the fusion of a male gamete and a female gamete produces a zygote.

(3) Embryo – the zygote divides a number of times by the process of mitosis and results in the formation of the embryo.

(4) Seedling- the embryo differentiates and becomes plumule, radicle and one or two cotyledons.

Question:4

Offspring formed by the asexual method of reproduction have greater similarity among themselves because
(i) asexual reproduction involves only one parent
(ii) asexual reproduction does not involve gametes
(iii) asexual reproduction occurs before sexual reproduction
(iv) asexual reproduction occurs after sexual reproduction
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)

Answer: A

Solution: In asexual reproduction, only a single parent is involved and offspring are directly produced from the parent by cell division, fragmentation, budding, etc., and it passes on the same genes from one generation to another. It does not involve any gametes. Thus, offspring formed by asexual reproduction have similarities among themselves.

Question:5

Characters transmitted from parents to offspring are present in
(a) cytoplasm
(b) ribosome
(c) golgi bodies
(d) genes

Answer: D

Solution: Genes are the unit of heredity. They are present on chromosomes, which are located in the nucleus of a cell. They carry genetic information from one generation to another and cause variation in the species.

Question:6

Characters that are transmitted from parents to offspring during reproduction show
(a) only similarities with parents
(b) only variations with parents
(c) both similarities and variations with parents
(d) neither similarities nor variations

Answer: C

Solution: The characters that pass on from parents to offspring show both similarity and differences. Similarity is because half of the chromosome comes from the father and another half comes from the mother. Variation is because of genetic recombination, mutation and natural selection.

Question:7

A feature of reproduction that is common to Amoeba, Spirogyra and yeast is that
(a) They reproduce asexually
(b) They are all unicellular
(c) They reproduce only sexually
(d) They are all multicellular

Answer: A

Solution: The common feature among amoeba, spirogyra and yeast is that they all reproduce by the asexual method of reproduction. Amoeba reproduces by binary fission, Spirogyra by fragmentation and yeast by budding.

Question:8

In Spirogyra, asexual reproduction takes place by
(a) Breaking up of filaments into smaller bits
(b) division of a cell into two cells
(c) division of a cell into many cells
(d) formation of young cells from older cells

Answer: A

Solution: Spirogyra reproduces by both asexual and sexual method. They reproduce asexually by the process of fragmentation and sexually by conjugation. In fragmentation, spirogyra breaks into two or more segments and each segment results in the formation of new organism.

Question:9

The ability of a cell to divide into several cells during reproduction in Plasmodium is called
(a) budding
(b) reduction division
(c) binary fission
(d) multiple fission

Answer: D

Solution: Plasmodium reproduces both asexually and sexually. Under unfavourable conditions, plasmodium forms a cyst around it and divides multiple times by the process of multiple fission and results in the formation of number of new cells.

Question:10

The correct sequence of reproductive stages seen in flowering plants is
(a) gametes, zygote, embryo, seedling
(b) zygote, gametes, embryo, seedling
(c) seedling, embryo, zygote, gametes
(d) gametes, embryo, zygote, seedling

Answer: A

Solution: The process of reproduction is divided into different stages. The first stage is the production of male and female gamete i.e., pollen and ovule respectively. The pollen grain reaches the stigma of flower by the process of pollination. The pollen germinates and forms pollen tube that reaches to the ovary and then male gamete is released. Male gamete fuses with female gamete and results in the formation of zygote.

The zygote divides several times to form an embryo. Then, there is seed development. Flowering plant's seeds have three parts, embryo formed from zygote, endosperm formed by double fertilization and seed coat formed by maternal tissue of ovule. The seeds under favorable conditions, germinate to produce a seedling.

Question:11

The number of chromosomes in parents and offspring 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

Answer: B

Solution: The gametes are produced by the process of meiosis where the number of chromosome in each gamete is halved. At the time of fertilization, the zygote thus formed has a full set of chromosomes. Therefore, the number of chromosomes in parents and offsprings of a species remain constant.

Question:12

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

Answer: B

Solution: Rhizopus is a saprotrophic fungus which feeds on the dead and decaying matter of living organisms. The body of Rhizopus is made up of branching mycelia composed of three types of hyphae- rhizoids, stolons and unbranched sporangiophores. Hyphae are the filamentous structures that branch out and spread below the substratum surface, as in the case of bread.

Question:13

Vegetative propagation refers to the 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

Answer: B

Solution: Vegetative propagation is a type of asexual reproduction in which new plants are formed from the vegetative parts- stem, leaves, bud and root of the plants. The plants produced by vegetative propagation are genetically similar to the parent plant in all its characteristics.

Question:14

Factors responsible for the rapid spread of bread mould on slices of bread are
(i) a 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)

Answer: C

Solution: The factors responsible for the rapid spread of bread mold on slices of bread are the availability of moisture and nutrients in bread and the formation of round-shaped sporangia. The fungi spread rapidly through spores by sexual or asexual methods. The spores germinate under favorable conditions and produce new hyphae.

Question:15

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

Answer: D

Solution: The pollen tube helps in transporting pollen grains to the ovule, inside which eggs are present. The pollen germinates on the upper surface of the stigma. Hence, the length of the pollen tube will depend on the distance between the upper surface of the stigma and the lower part of the ovule, and it will ensure that pollen reaches the stigma and pollination is successful.

Question: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 fertilization, they give rise to fruits
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)

Answer: D

Solution: The statements (ii) and (iv) are true while statements (i) and (iii) are false because flowers are not always bisexual. They can be unisexual too. Only angiosperms produce flowers, while bryophytes, pteridophytes, and gymnosperms do not produce flowers.

Question:17

Which among the following statements are true for unisexual flowers?
(i) They possess both stamen and pistil
(ii) They possess either a stamen or a 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)

Answer: B

Solution: In case of angiosperms, flowers can be unisexual or bisexual. The unisexual flowers have either stamens or pistils. Cross pollination is necessary in the case of unisexual flowers. In both types of flowers, the pistil bears an ovary. Fruit is ripened or matured ovary. After fertilization ovary undergoes major changes and its wall also thickens to produce a fruit. Flowers possessing only stamens cannot produce fruits because a fruit is a mature ovary.

Question:18

Which among the following statements are true for sexual reproduction in flowering plants?
(i) It requires two types of gametes
(ii) Fertilization is a compulsory event
(iii) It always results in the formation of a 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)

Answer: C

Solution: Sexual reproduction is the process in which two parents i.e., male and female are involved. Male produces male gamete while female produces female gamete. During fertilization, the male and female gamete fuses to form the zygote. Reproduction is necessary for the continuation of the species. The offsprings resulting from asexual reproduction are exactly identical to the parents and are called as clones.

Question:19

In Figure 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

Answer: C

Solution: A represents the plumule that results in the formation of a shoot. B represents the cotyledon where the food is stored. C represents the radicle, which forms the roots. The embryonic axis comprises a plumule and radicle, present on opposite sides of the point of attachment of cotyledons to the embryonic axis.

Question: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

Answer: B

Solution: Sexual reproduction is the process in which two individuals of the same species produce two different gametes, i.e., one male gamete and another female gamete. These gametes, upon fusion, result in the formation of the zygote, which produces new offspring. Because of the contribution of two parents, offspring produce more variations.

Question:21

Reproduction is essential for living organisms in order to
(a) keep the individual organism alive
(b) fulfill their energy requirement
(c) maintain growth
(d) continue the species generation after generation

Answer: D

Solution: Reproduction is essential for the survival of the species because it helps in producing a new generation of the same species. All other life processes are essential to keep the organisms alive

Question:22

During adolescence, several changes occur in the human body. Mark one change associated with sexual maturation in boys
(a) loss of milk teeth
(b) increase in height
(c) cracking of voice
(d) weight gain

Answer: C

Solution: The Following changes occur in the body of the boys during adolescence-

• The growth of hair in different parts of the body, like the face, armpits, chest and between the thighs near the genitals.

• Cracking of voice

• Broadening of shoulders

• Erection of penis

Question:23

In human females, an event that reflects the onset of the reproductive phase is
(a) growth of the body
(b) changes in hair pattern
(c) change in voice
(d) menstruation

Answer: D

In females, menstruation marks an event that reflects the onset of the reproductive phase. This phase is marked by the discharge of the endometrial lining and the unfertilized egg through the vagina. This process continues for about 5-7 days.

Question:24

In human males, the testes lie in the scrotum, because it helps in the
(a) process of mating
(b) formation of sperm
(c) easy transfer of gametes
(d) all the above

Answer: B

Testes is present in a muscular bag called as scrotum which lies outside the body cavity. Testes help in the formation of sperms because the sperm production requires lower temperature than the body.

Question:25

Which among the following is not the function of the testes at puberty?
(i) formation of germ cells
(ii) secretion of testosterone
(iii) development of the placenta
(iv) secretion of estrogen
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)

Answer: C

Gonads help in the production of hormones and gametes. In case of males, the testes produce sperm and testosterone. The placenta is formed in females during pregnancy. It has some functions, like the production of hormones, nutrition, excretion, etc. Estrogen is a female hormone produced by the ovaries.

Question:26

The correct sequence of organs in the male reproductive system for the transport of sperm is
(a) testis $\to$ vasdeferens $\to$ urethra
(b) testis $\to$ ureter $\to$ urethra
(c) testis $\to$ urethra $\to$ ureter
(d) testis $\to$ vasdeferens $\to$ ureter

Answer: A

Solution: Testes produce sperms which are stored in the epididymis and are transported to the urethra through vas deferens.

The correct sequence is- testis $\to$ vasdeferens $\to$ urethra

Question:27

Which among the following diseases is not sexually transmitted?
(a) Syphilis
(b) Hepatitis
(c) HIV - AIDS
(d) Gonorrhoea

Answer: B

Solution: Syphilis and Gonorrhoea are sexually transmitted diseases. Syphilis is caused by Treponema pallidum, and gonorrhoea is caused by Neisseria gonorrhoeae.

AIDS is a sexually transmitted viral disease caused by HIV.

Hepatitis is caused through contaminated water and food. In hepatitis, the inflammation of the liver is caused by the virus which spreads through body fluids, blood etc of the person suffering from the disease.

Access Answers to Chapter 8 NCERT Exemplar Class 10 Science (Short Answer)

The detailed short answers to the solutions are given below:

Question:28

In a bisexual flower despite the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for the above situation.

Answer:

Even though the young stamens (produce pollen grains) are being removed, carpel (producing eggs) exhibits cross pollination either with the flower of same plant or different plant of same species termed Geitonogamy and Xenogamy respectively.

Papaya is a dioecious plant, which has either male or female flowers on a tree. Yet the female tree produces fruits by cross pollination. The male tree doesn’t bear any fruit.

By removing stamens of a flower, only autogamy is prevented, but not Geitonogamy or Xenogamy.

Question:29

Can you consider cell division as a type of reproduction in unicellular organisms? Give one reason.

Answer:

Unicellular organisms reproduce asexually by cell division of parent cell. Parent cell divides into two daughter cells. Here parent cell does not tend to get old and die therefore unicellular organisms are even considered as biologically immortal.

Hence, cell division can be considered as a mode of reproduction in single celled organisms, eg., Amoeba.

Question:30

What is a clone? Why do offspring formed by asexual reproduction exhibit remarkable similarity?

Answer:

Clone refers to either a group of cells or organisms which are produced asexually from a cell or individual organism. Clones exhibit remarkable

similarity because they possess exact copies of the DNA of their parent.

Clones are produced by asexual means from a single parent, so these cells tend to have similar genetic material to a parent because of asexual reproduction

shows no gamete formation by meiosis or fertilization of male and female gametes.

Hence, offspring of asexual reproduction are similar among themselves and with the parent organism, as there is no genetic recombination.

Question:31

Explain how offspring and parents of organisms reproducing sexually have the same number of chromosomes.

Answer:

Meiosis is also known as the reductional division is responsible for the formation of gametes. Meiosis reduces the number of chromosomes to half in male and female gametes.

For example, an organism with the diploid condition (2n) has 20 chromosomes, then its gametes are haploid (n) with 10 chromosomes.

After fertilization of the male (n) and female gametes (n), the zygote formed will be diploid (2n). Hence, fertilization restores the normal chromosome number of organisms.

Question:32

Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this.

Answer:

Colonies of yeast fail to multiply in water but multiply in sugar solution.

Water does not have all the required nutrients necessary for growth and reproduction of yeast cell whereas sugar solution serves as an organic source for cellular respiration which releases energy for necessary cellular activities such as reproduction. That is why yeast fail to multiply in water.

Question:33

Why does bread mould grow profusely on a moist slice of bread rather than on a dry slice of bread?

Answer:

Moist conditions are suitable for the germination of spores and the growth of hyphae. Even though bread is a suitable source of nutrients but dry conditions wouldn’t allow spores to germinate.

That is why bread mould grows profusely on a moist slice of bread rather than on a dry slice.

Question:34

Give two reasons for the appearance of variations among the progeny formed by sexual reproduction.

Answer:

Meiosis and fertilization are the two reasons for the appearance of variations in sexual reproduction. There is an event in meiosis termed crossing over, which leads to genetic recombination and variation. In fertilization, a random fusion of two gametes of different genetic lines is responsible for the variation.

Question:35

Would a Planaria cut vertically into two halves regenerate into two individuals? Complete Figure 8.2 D and E by indicating the regenerated regions.

Answer:

Yes, a Planaria cut vertically into two halves regenerates into two individuals because planaria exhibits regeneration. The shaded part in Figures D and E represents the regenerated halves.

Question:36

From the internet, gather information about the chromosome numbers of five animals and five plants. Correlate the number with the size of the organism and answer the following questions.
(a) Do larger organisms have more chromosomes/cells?
(b) Can an organism with fewer chromosomes reproduce more easily than an organism with more chromosomes?
(c) The greater the number of chromosomes/cells greater is the DNA content. Justify.

Answer:

Rice 24 Housefly 8

Apple 34 Dog 78

Potato 48 Butterfly 380

Onion 16 Human 46

Maize 20 Rat 42

(a) No, there is no relation between the size of the organism and the number of chromosomes.

(b) No, the reproduction process depends on environmental factors such as availability of water, pollinators, etc. and not on the number of chromosomes

in organisms.

(c) Yes, genes are segments of DNA. DNA is closely packed into chromosomes, hence, more chromosome means greater DNA.

Question:37

In tobacco plant, the male gametes have twenty four chromosomes. What is the number of chromosomes in the female gamete? What is the number of chromosomes in the zygote?

Answer:

We know that Gametes have a haploid number of chromosomes that are present in both gametes. Given that the male gamete has 24 chromosomes, the female gamete also has 24 chromosomes. By fusion of gametes to form a zygote, the zygote reestablishes 48 chromosomes.

Hence,

Number of chromosomes in a female gamete of a tobacco plant-24

Number of chromosomes in zygote-48

Question:38

Why cannot fertilization take place in flowers if pollination does not occur?

Answer:

Fertilization cannot take place in flowers if pollination does not occur because, without pollination, no male and female gametes can come closer. Pollination is the process by which the pollen is transferred from the anther or male part to the stigma or the female part of the plant. Fertilization requires male and female gametes. Hence, pollination of any kind (autogamy, geitonogamy, xenogamy) is required to get male and female gametes closer.

Question:39

Is the chromosome number of zygotes, embryonal cells and adults of a particular organism always constant? How is the constancy maintained in these three stages?

Answer:

Yes, the chromosome number of the zygote, embryonal cells and adult of a particular organism is always constant. Sexual reproduction includes gamete formation through meiosis and fertilization. Meiosis reduces the number of chromosomes to half in male and female gametes. This reduced chromosome number is then restored to normal during fertilization of male and female gametes. A zygote is formed by the fusion of gametes.

Once formed, it undergoes mitotic divisions. Embryonal cells also divide by mitosis to produce more of its kind. The cells in the adult organism also divide by mitosis. Hence mitosis in gamete formation and fertilization together maintain the chromosome number in the zygote. Embryo and adult form is formed from zygote by mitosis division (equational division).

Question:40

Where is the zygote located in the flower after fertilization?

Answer:

Zygote is located inside the female gametophyte (embryo sac) which is located inside ovule. After fertilization, ovule transforms into seeds and ovary into fruit.

Question:41

Reproduction is linked to the stability of the population of a species. Justify the statement.

Answer:

Reproduction is the process of production of organisms of its own kind and maintaining continuity generations after generations. Reproduction produces offspring's which are with some similarities and variations with parents' due to genetic recombination and fertilization.

This ensures them to overcome struggles such as competition for natural resources, habitation, predation etc. This is how reproduction ensures the stability of species and genetic heredity of characters.

Question:42

How are general growth and sexual maturation different from each other?

Answer:

General growth is associated with an increase in several cells, size, weight, and height of an organism. General growth is also referred to as the somatic phase of growth, which is similar in both sexes, and reproductive organs are less active.

Sexual growth includes all the changes body undergoes for sexual reproduction. It ensures onset of puberty and reproductive phase in an individual. Sexual growth is different in both sexes with noticeable changes such as beard and mustache in males, and high-pitched voice and onset of menstruation in females.

Question:43

Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system.

Answer:

Testis - Epididymis - Vas deference - Urethra

Testis secretes androgens (testosterone).

The prostate gland secretes thin milky alkaline fluid that adjusts the pH of seminal fluid and serves in the motility of sperm. Bulbourethral glands/Cowper gland secretions are meant for the lubrication of penis during sexual intercourse. Seminal vesicles add fructose (nutrient), calcium (mineral element), and alkaline pH to counteract the acidic pH of the vagina

Question:44

What changes are observed in the uterus if fertilization does not occur?

Answer:

In the absence of pregnancy, there is an abrupt fall in the progesterone levels, which disintegrates the thickened endometrium and sloughs off during the menstruation phase (1-5 days). There will be a drop in the hormone levels, which will cause the uterus to shed its lining and egg in the process called menstruation, where there is blood and uterine secretions are removed through the vagina.

Question:45

What changes are observed in the uterus after the implantation of the young embryo?

Answer:

Ruptured graafian follicle transforms into corpus luteum which secrets progesterone which is necessary for thickening of endometrium. Disc like structure is formed by interdigitation of maternal tissue and embryonal tissue which is referred as placenta.

Placenta serves to provide nutrients and oxygen from mother's blood to embryo and also removes waste generated by embryo. The embryo and placenta are connected by umbilical cord.

Question:46

What are the benefits of using mechanical barriers during sexual activity?

Answer:

The benefits of using mechanical barriers during the sexual act are:

(i) It serves as a barrier to prevent unwanted pregnancies and acts as a gap between the offspring.

(ii) It also protects from sexually transmissible diseases (STDs).

Question:47

In the given Figure 8.3, label the parts and mention their functions

(a) Production of eggs
(b) Site of fertilization
(c) Site of implantation
(d) Entry of the sperm

Answer:

(a) OVARY - production of egg.

(b) OVIDUCT - site of fertilization.

(c) UTERUS - site of implantation.

(d) VAGINA - passage for entry of sperms.

Question:48

What would be the ratio of chromosome number between an egg and its zygote? How is the sperm genetically different from the egg?

Answer:

The ratio of number of chromosomes in egg and zygote is 1:2. The egg is formed by reductional division from the parent cell. Zygote (2n) is formed by fertilization of male (n) and female (n) gametes. Sperms are different from eggs by chromosome number 23 as sperm can either be X or Y chromosome whereas egg has an only X chromosome.

Find Answers to Class 10 Science NCERT Exemplar Chapter 8(Long Answer)

The detailed long answers to the solutions are given below:

Question:49

Why are budding, fragmentation and regeneration all considered as asexual types of reproduction? With neat diagrams, explain the process of regeneration in Planaria.

Answer:

Asexual reproduction is uniparental and it does not involve gamete formation and fertilization. As fragmentation, budding and regeneration none of these involves gamete formation & fertilization, and all of them produce individuals from single parents only hence these are considered as asexual reproduction.

Regeneration is asexual reproduction in which an organism can regenerate the lost or damaged body parts, for example, if a planaria is cut into small pieces, then each piece develops into a new individual.

Question:50

Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction.

Answer:

Variations are seen in sexual reproduction because of the fusion of genetically different gametes- fertilization. Gametes are formed by meiosis, where there is an event termed crossing over, which leads to genetic recombination. Even an independent assortment of gametes is also responsible for variations in sexual reproduction.

Question:51

Distinguish between pollination and fertilization. Mention the site and product of fertilization in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule.

Answer:

Site of fertilization is female gametophyte (embryo sac) inside an ovule. Products of fertilization are zygote formation, the transformation of ovule into seeds, ovary into fruits.

Question:52

Distinguish between a gamete and a zygote. Explain their roles in sexual reproduction.

Answer:

ROLE OF GAMETES AND ZYGOTE IN SEXUAL REPRODUCTION:

Gametes are the product of meiosis and hence carry half the chromosome number of the parent cells. This chromosome number is restored during fertilization and zygote formation. Hence, gamete and zygote are the two phases of sexually reproducing organisms that help maintain the constant chromosome number in each species.

Question:53

Draw the diagram of a flower and label the four whorls. Write the names of gamete-producing organs in the flower.

Answer:

Four whorls of a flower are

• CALYX- Sepals

• COROLLA- Petals

• ANDROECIUM- male reproductive structure, stamens.

• GYNOECIUM- female reproductive structure, pistil.

Gametes producing organs:

• Anthers (Part of androecium) - male gametes

• Ovary (Part of gynoecium) - female gamete

Question:54

What is the placenta? Mention its role during pregnancy?

Answer:

The placenta is formed by the outer layer of trophoblasts of the embryo and endometrium. It starts to form after the implantation of the blastocyst around 12 weeks of pregnancy. It is a disc-like structure formed by interdigitation of maternal tissue and chorionic villi of embryonal tissue, forming a structural unit referred to as the placenta.

Placenta serves to provide nutrients and oxygen from the mother's blood to embryo and also removes waste generated by the embryo. The fetus and placenta are connected by the umbilical cord.

Question:

What are various ways to avoid pregnancy? Elaborate on any one method.

Answer:

Various ways to avoid pregnancy:

Natural methods

(a) Periodic abstinence - abstain from sexual intercourse during the fertile period (10-17 days of the menstrual cycle)

(b) Lactational amenorrhea - ovulation generally will not occur during the period of intense lactation.

Barrier methods

(a) Condoms - made of thin rubber latex sheath, prevent ejaculated sperm from reaching the uterus.

(b) Other barrier methods are diaphragms, cervical caps, and vaults

Intrauterine devices – These are devices inserted into the uterus by doctors or trained nurses through the vagina. These are of different types, such as non-medicated (Lippes Loop), copper-releasing (Cu T, multi-load 375), and hormone-releasing (Progestasert, LNG-20).

Oral contraceptive pills – Oral administration of small doses of progesterone – estrogen combination in the form of pills, eg, Saheli.

Surgical methods - Vasectomy (vas deferens are cut and tied, ensuring the absence of sperm in semen), tubectomy (fallopian tubes are cut and tied, preventing the ovum from reaching the uterus).

Question:56

How does fertilization take place? Fertilization occurs once a month. Comment.

Answer:

The sperms released during sexual intercourse enter through the vagina and travel upwards and reach the oviducts which is the site of fertilization, where they fuse with the egg forming zygote which gets implanted in the uterus. Millions of sperm are released during ejaculation during sexual intercourse, but only one sperm gets to fuse with the ovum. Ovulation release of the ovum from the ovary, occurs only once a month on the 14th day of the menstrual cycle. Hence, fertilization can occur only once a month.

Question:57

Reproduction is essentially a phenomenon that is not for the survival of an individual but for the stability of a species. Justify.

Answer:

Reproduction is the process of producing organisms of its kind and maintaining continuity from generation to generation. Reproduction produces offspring's which are with some similarities and variations with parents due to genetic recombination occurred during gamete formation by crossing over and independent assortment and fertilization of male and female gametes. Such variation ensures them to overcome struggles such as competition for natural resources, habitation, predation etc.

Therefore, reproduction not only restores the number of individuals removed from the species by above mentioned natural forces but also maintain heredity of genetic characters and introduction of variations, as needed for continuity and stability of a species.

Question:58

Describe sexually transmitted diseases and mention the ways to prevent them.

Answer:

Sexually transmitted diseases/venereal diseases/ reproductive tract infections. STDs are infectious diseases transmitted by sexual intercourse and bodily fluids such as semen, blood etc. Few STDs and their causative organisms

Preventive measures:

(I) Avoid sex with multiple partners

(ii) avoid unprotected sexual activities and maintain personal hygiene.

(iii) stop sharing needles, as there are chances for the transmission of bodily fluids.

Read more NCERT Notes Subject Wise

• NCERT Notes for Class 10 Science

• NCERT Notes for Class 10 Maths

Overview of Chapter 8 for Class 10 Science

The Chapter How Do Organisms Reproduce? discusses the intriguing and basic process of reproduction in organisms such as plants and animals. Reproduction is inherent to the life cycle, being responsible for continuing life and giving rise to like organisms, assuring the population and survival of species. Through this chapter, the different reproductive methods and how they are relevant are discussed. It is by understanding the different ways organisms produce offspring that leads to an apprehension of important biological principles.

• NCERT Solution for Class 10 Science

• NCERT Solution for Class 10 Maths

Key topics covered in Chapter 8"How Do Organisms Reproduce?"

This chapter focuses on the biological process of reproduction, which is vital for the survival and continuity of species. Below is a detailed breakdown of the key topics covered:

1. Significance of Reproduction

Reproduction is a process by which organisms make offspring to continue their species. It also provides a variation that aids in evolution.

2. Methods of Reproduction

The different methods of Reproduction are:

Asexual Reproduction:

Has a single parent.

Offspring are genetically similar to the parent.

Examples:

• Binary Fission (In Amoeba and Paramecium)
• Budding (In Hydra and yeast)
• Fragmentation (In plants such as Spirogyra)
• Spore formation fungi such as Rhizopus.
• Vegetative Propagation (Expressed in plants such as potatoes and Bryophyllum)

Sexual Reproduction:

Involves two parents sharing genetic material.

Results in genetic diversity.

Examples:

• Sexual reproduction in flowering plants
• Pollination and fertilization.
• In animals, Fertilization results in the formation of a zygote.
• Reproductive system in humans (male and female reproductive organs)

3. Reproductive Health

• Need for reproductive health
• Contraceptive methods and population control

Important diagrams in Class 10 Science Chapter 8

Here are some important diagrams from "How Do Organisms Reproduce?":

Multiple Fission in Plasmodium

This diagram shows multiple fissions in Plasmodium, demonstrating how it can produce many daughter cells simultaneously.

Regeneration in Planaria

This diagram depicts the process of regeneration, showing how Planaria can grow new individuals from body parts.

Human Female Reproductive System

This diagram shows the anatomy of the female reproductive system, highlighting key organs involved in reproduction.

Germination of Pollen on Stigma

This diagram depicts how pollen germinates on the stigma of a flower, leading to fertilization.

Binary Fission in Amoeba

This diagram shows how an Amoeba reproduces by binary fission, dividing into two identical cells.

NCERT Class 10 Science Exemplar Solutions for Other Chapters:

Below are the chapters to go through:

NCERT Class 10 Science Exemplar Solutions Chapter 8- Types of Questions and Their Weightage in Board Exams

In Class 10 Science, the students have to answer very short answers, short answers, long answers, and practical-based questions in the CBSE board examination. These questions generally hold 1 to 5 marks and test students' knowledge of reproduction in organisms.

These solutions are extremely important in enabling students to get 8–10 marks in board exams. Through the strict practice of questions and answers in this chapter, students can reinforce their understanding of important concepts and improve their performance in exams.

CBSE board exam aspirants can take advantage of these solutions to make their exam preparation complete.

Also, check NCERT Books and NCERT Syllabus here

• NCERT Books Class 10 Science

• NCERT Syllabus Class 10 Science

• NCERT Books Class 10

• NCERT Syllabus Class 10

Topics Covered in NCERT Exemplar Class 10 Science Solutions Chapter 8:

The topics covered are mentioned below:

• Different methods and processes of reproduction.

• These solutions discuss the reproduction process of plants and animals.

• Similarity as well as dissimilarity between the production processes of plants and animals.

• Organs are responsible for reproduction in any organism.

NCERT Class 10 Exemplar Solutions for Other Subjects:

• NCERT Exemplar Class 10 Maths solutions

• NCERT Exemplar Class 10 Science solutions

CBSE NCERT Solutions for Class 10 Science - Chapter-wise

Below mentioned are the Chapterwise solutions:

In short, the NCERT Exemplar Class 10 Science Solutions for Chapter 8, is helpful for students aspiring to appear for board exams as well as competitive exams like NEET. By providing detailed and simple answers to various questions, from MCQs, SAQs, and LAQs, these solutions make students conceptually strong in terms of reproduction in organisms. Practising using these solutions regularly will certainly enable students to understand better and score well in exams.

Check NCERT Solutions for questions given in the book