Chapter 24: REPRODUCTION

Chapter 24: Reproduction Class 10 Science and Technology (212) NIOS Textbook Solutions

Chapter 24. REPRODUCTION

INTEXT QUESTIONS 24.1

1. Define reproduction.

Answer: Reproduction is the biological process in which living organisms produce new individuals of their own species, ensuring the continuation of life.

2. State one point of difference between asexual and sexual reproduction.

Answer: Asexual reproduction involves only one parent and no fusion of gametes, while sexual reproduction involves two parents and fusion of male and female gametes.

3. Why is binary fission considered to be an asexual form of reproduction .

Answer: Binary fission is considered asexual reproduction because it involves only one parent organism and does not involve the formation or fusion of gametes. In this process, the parent cell simply divides into two identical daughter cells, which are genetically the same as the parent.

4. Define vegetative propagation with the help of an example.

Answer: Vegetative propagation is a type of asexual reproduction in which new plants develop from the vegetative parts of a plant such as roots, stems, or leaves.

For example, in Bryophyllum, new plants grow from the buds present on the edges of its leaves.

5. Define the following (i) callus (ii) clone

Answer: (i) Callus is an undifferentiated mass of cells that is formed when plant cells are grown in a culture medium.

(ii) Clone is a genetically identical copy of the parent organism, formed through asexual reproduction. For example, Dolly the sheep was a cloned animal.

INTEXT QUESTIONS 24.2

1. What purpose does the flower serve in a plant?

Answer: The flower serves as the reproductive organ of a plant.

2. Give one point of difference between self pollination and cross pollination.

Answer: Self-pollination is the transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant, while cross-pollination is the transfer of pollen from the anther of one plant to the stigma of a flower on another plant of the same species.

3. What will happen if the pistil of the flower is removed?

Answer:  If the pistil of a flower is removed, fertilisation will not take place because the pistil contains the ovary and ovules which are needed for seed formation. As a result, the flower will not produce seeds or fruits.

4. Trace the path of the pollen after it lands on the stigma.

Answer: After the pollen grain lands on the stigma, it absorbs moisture and germinates. A pollen tube grows down through the style and reaches the ovary. The male gamete then travels through the pollen tube and enters the ovule, where fertilisation takes place by fusing with the egg cell.

5. What is germination of seed?

Answer: Germination of a seed is the process in which a seed develops into a new young plant under suitable conditions like water, air, and warmth.

INTEXT QUESTIONS 24.3

1. Define the terms (i) adolescence (ii) puberty (iii) hermaphrodite (iv)oviparous

(v) viviparous (vi) foetus

Answer: (i) Adolescence: The stage of life between about 11 to 19 years when major physical and physiological changes take place in the body.

(ii) Puberty: The time period when changes occur in the body that make a human capable of reproduction.

(iii) Hermaphrodite: An organism that has both male and female reproductive organs in the same individual.

(iv) Oviparous: Animals in which the development of the embryo takes place inside an egg, either partly or completely.

(v) Viviparous: Animals in which the young ones develop inside the mother’s body and are born alive.

(vi) Foetus: The stage of development in which the embryo is implanted in the uterus wall of the mother and shows further growth.

2. Name the hormones secreted by the testes and ovary.

Answer: The testes secrete the hormone testosterone, and the ovaries secrete the hormones oestrogen and progesterone.

3. Name the part of the female reproductive system where the egg gets fertilized by the sperm.

Answer: The fertilisation of the egg by the sperm takes place in the oviduct (fallopian tube) of the female reproductive system.

4. State the function of (i) uterus (ii) vas deferens

Answer: (i) Uterus: It is the organ where the fertilised egg gets implanted and the embryo develops into a foetus during pregnancy.

(ii) Vas deferens: It is a tube that carries sperm from the testes to the urethra for ejaculation.

5. Consider the three case studies given below. Please provide your suggestions for managing these situations in 2-4 sentences each.

Case 1: Your friend, Suresh is extremely shy and withdrawn because he is growing hair at many places in his body. His voice is croaky and sometimes he gets dreams which make him feel ashamed of himself. How will you convince Suresh that what he is undergoing is absolutely normal and natural?

Case 2: Rehman, your friend , is disappointed because he is the same age as

most of the friends but in comparison to others, he looks baby-faced and has no facial hair. How will you get him out of this ‘odd man out’ feeling? Suggest two ways.

Case 3: Your cousin Madhu is prevented from entering the kitchen and entering places of worship during menstruation and Madhu feels that she is being punished for something that is normal and definitely not her fault.

Based on your understanding of menstrual cycle, do you think this is a correct practice? If not, please provide at least two reasons to convince your aunt to stop this practice.

Answer: Case 1: Suresh is going through puberty, and all these changes like body hair growth, voice change, and dreams are completely normal. These are natural hormonal changes that happen in every boy during adolescence. He should not feel ashamed because it is a part of growing up.

Case 2: Rehman should understand that puberty happens at different ages for different people, so his growth is still normal. Some boys develop facial hair later than others, and it does not mean anything is wrong. He should stay confident and give his body time to develop naturally.

Case 3: No, this practice is not correct. Menstruation is a normal biological process and not a sign of impurity or punishment. It is caused by natural hormonal changes in the body, so there is no scientific reason to restrict Madhu from entering the kitchen or places of worship. Such restrictions can create unnecessary stress and discrimination, so they should be stopped.

6. Your friend Kiran would not look at boys during her periods as she had heard from someone that if she did so she would become pregnant.

Write a letter to Kiran that helps her realize that she is holding on to a false belief.

Answer: Dear Kiran,

I hope you’re doing well. I wanted to talk about something you mentioned regarding your periods. Please know that looking at boys or anyone during your periods cannot make you pregnant. Pregnancy happens only when a sperm meets an egg in the fallopian tube, and that requires sexual contact, not eye contact.

Periods are a normal and healthy part of growing up, and they don’t change your ability to interact with others. The belief you heard is just a myth, so please don’t let it make you feel awkward or restricted. You are free to talk, laugh, and look at anyone without worry.

If you ever have any questions, I’m here to help. Take care of yourself!

                                                            With love,
                                                          [Your name]

INTEXT QUESTIONS 24.4

1. List, in a sequence the events that lead to the birth of a new individual.

Answer: The sequence of events that lead to the birth of a new individual are:

(i) Formation of male and female gametes (sperm and egg).

(ii) Fusion of gametes (fertilisation) to form a zygote.

(iii) Repeated cell division of the zygote to form an embryo.

(iv) Implantation of the embryo in the uterus wall.

(v) Development of embryo into a foetus.

(vi) Completion of gestation period and birth of the baby.

2. Name the hormones responsible, for attaining reproductive maturity, and for formation and maturing of sperms and eggs in humans.

Answer: The hormones responsible for attaining reproductive maturity and for the formation and maturation of sperms and eggs in humans are FSH (Follicle Stimulating Hormone) and LH (Luteinising Hormone).

3. Given below is a list of hormones related to reproduction. List influence on functions in the space given below:   FSH, LH, Estrogen, Testosterone, Oxytocin

Hormones	Function

Answer:

Hormones	Function
FSH LH Estrogen Testosterone Oxytocein	Egg mature Egg shed Secondary sexual characters in female Secondary sexual characters in male Uterine contractions for deliver the baby

INTEXT QUESTIONS 24.5

1. Name any four sexually transmitted diseases.

Answer: Four sexually transmitted diseases are syphilis, gonorrhea, herpes and Chlamydia.

2. Name four devices which prevent fertilization in humans.

Answer: Four devices used to prevent fertilisation in humans are IUCD – Copper T, oral contraceptive pills, vasectomy in male/tubectomy in female and MTP.

3. Expand the abbreviations (i) HIV and (ii) AIDS.

Answer: (i) HIV – Human Immunodeficiency virus

(ii) AIDS – Acquired Immuno Deficiency Syndrome

TERMINAL EXERCISES

1. Name the biological process by virtue of which a species continues from generation to generation?

Answer: The biological process by which a species continues from generation to generation is reproduction.

2. Mention two differences between asexual and sexual modes of reproduction?

Answer: The differences between asexual and sexual modes of reproduction :

Asexual reproduction	Sexual reproduction
Involves only one parent	Involves two parents
No fusion of gametes takes place	Fusion of male and female gametes takes place

3. Mention an example for each of the following methods of reproduction.

(i) Budding    (ii) Spore formation    (iii) Binary fission   (iv) Vegetative reproduction

Answer: (i) Budding → Hydra or yeast
(ii) Spore formation → Rhizopus (bread mould)
(iii) Binary fission → Amoeba
(iv) Vegetative reproduction → Bryophyllum

4. Why is vegetative reproduction considered as a type of asexual reproduction?

Answer: Vegetative reproduction is considered a type of asexual reproduction because it involves only one parent plant and there is no fusion of gametes. The new plant develops from vegetative parts like roots, stems, or leaves and is genetically identical to the parent plant.

5. Mention the specialized parts that are responsible for vegetative mode of reproduction in the following plants

(i) Ginger (ii) Grass    (iii) Onion (iv) Potato

Answer: The specialized parts responsible for vegetative reproduction are:

(i) Ginger – Rhizome (underground stem)
(ii) Grass – Runner (stolon)
(iii) Onion – Bulb
(iv) Potato – Tuber

6. How is artificial vegetative propagation different from natural vegetative propagation. How is the former beneficial to humans?

Answer:

Natural vegetative propagation	Artificial vegetative propagation
It occurs naturally without human involvement.	It is done by humans using scientific methods.
New plants grow from natural parts like roots, stems, or leaves.	New plants are produced using methods like cutting, grafting, layering, etc.
It is a slow and less controlled process.	It is faster and allows production of desired plant varieties.

It helps humans produce plants faster in large numbers with desired qualities. The new plants are genetically identical, so good traits like better yield, disease resistance, and quality are maintained.

7. How is a callus developed in tissue culture? Give the steps.

Answer: Steps for development of callus in tissue culture:

(i) A small piece of plant tissue (called explant) is taken from a healthy plant.

(ii) The explant is placed in a sterile nutrient culture medium.

(iii) Plant hormones like auxins and cytokinins are added to the medium.

(iv) The cells of the explant start dividing rapidly in an unorganised way.

(v) This mass of undifferentiated cells formed is called a callus.

8. Why is it said that all living cells are totipotent? Explain.

Answer: All living cells are said to be totipotent because each one contains the complete set of genetic information (DNA) present in the zygote. This means that under suitable conditions, a single living cell has the inherent capacity to divide, differentiate, and develop into a whole new organism, just like the parent plant. This property is the fundamental basis for both natural and artificial vegetative propagation.

9. Label the following parts in the given diagram

(i) part that produces pollen.

(ii) part of the flower that receives the pollen.

(iii) part that contains ovules.

(iv) the part of the flower that holds the anther.

Answer: Photo

(i) Part that produces pollen – Anther
(ii) Part of the flower that receives the pollen – Stigma
(iii) Part that contains ovules – Ovary
(iv) The part of the flower that holds the anther – Filament

10. Justify the following statements:

(i) Birds, reptiles and frogs are called ‘Oviparous’.

(ii) Human are ‘Viviparous’.

(iii) Earth worm is a ‘hermaphrodite’.

(iv) The sheep ‘Dolly’ was a clone of her mother.

Answer: (i) Birds, reptiles and frogs are called oviparous because they lay eggs and the development of the embryo takes place inside the egg.

(ii) Humans are viviparous because the baby develops inside the mother’s uterus and young ones are born alive.

(iii) Earthworm is a hermaphrodite because it possesses both male and female reproductive organs in the same individual.

(iv) The sheep Dolly was a clone of her mother because she was produced artificially and was genetically identical to the parent from which the cell was taken.

11. Trace the events after pollination that lead to seed formation

Answer: After pollination, the pollen grain germinates on the stigma and grows a pollen tube down the style. The tube enters the ovule through the micropyle and releases two male gametes. One gamete fuses with the egg cell (fertilization) to form a zygote. The other fuses with the polar nuclei to form the endosperm (triple fusion). The zygote develops into an embryo, the ovule becomes the seed, and the ovary matures into the fruit.

12. Identify (a) (b) (c) and (d) in the following table

Reproductive organ of Human                                      Function

1. Testes                                                                  1) Produces the hormone.........(a)......

2. ........(b).......................                                      2) The womb in which the embryo develops

3. Cervix 3) ........(c)............................

4. ........(.d..)......................          4) Arise from he testis and later join together to form ejaculatory duct.

Answer:

Reproductive organ of Human	Function
1. Testes	Produces the hormone (a) Testosterone
2. (b) Uterus	The womb in which the embryo develops
3. Cervix	(c) Opening of the uterus into the vagina / lower narrow part of the uterus
4. (d) Vas deferens	Arise from the testis and later join together to form the ejaculatory duct

13. List the physiological changes that arise at puberty in

(i) human female     (ii) human male

Answer: (i) Physiological changes at puberty in human female:

(a) Development of breasts

(b) Growth of hair in the armpits and pubic region  

(c) Widening of hips

(d) Beginning of menstruation and release of eggs

(e)Increase in height and body growth

(ii) Physiological changes at puberty in human male:

(a) Growth of hair on the face, armpits, chest, and pubic region

(b) Deepening of voice

(c) Broadening of shoulders and increase in muscle development

(d) Enlargement of testes and penis

(e) Beginning of sperm production and increase in height

14. Mention the psychological changes that are experienced by the adolescents.

Answer: The psychological changes experienced during adolescence are:

(i) Adolescents are capable of abstract thinking.

(ii) They experience mood swings.

(iii) They become self conscious.

(iv) Self image and identity becomes important.

(v) Friendship is very important to them.

(vi) They start getting interested in one another in a sexual way.

15. Mention the fate of the thickened uterine lining in human of in case fertilisation does not occur.

Answer: If fertilisation does not occur, the thickened uterine lining breaks down and is shed from the body along with blood and mucus through the vagina. This process is called menstruation.

16. Do you agree with the statement “A strong force of one billion Indians can achieve all the developmental goals and lot more”? Why/Why not?

Answer: Yes, I agree with the statement “A strong force of one billion Indians can achieve all the developmental goals and a lot more.”

India has a large population which can become a great strength if people are educated, healthy, skilled, and provided with equal opportunities. When citizens work together and contribute positively in areas such as education, science, technology, agriculture, and social development, the country can achieve rapid progress and development goals.

17. Why is it that -

(i) Women acquire STIs more easity as compared to men?

(ii) Young women are more susceptible to acquire STIs as compared to men?

Answer: (i) Women acquire STIs more easily as compared to men because the female reproductive tract has a larger surface area and delicate tissues, making it easier for disease-causing microorganisms to enter the body.

(ii) Young women are more susceptible to acquire STIs as compared to men because their reproductive organs are still developing and the protective lining of the reproductive tract is comparatively less mature, making infections easier to occur.

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