Chapter 24: Reproduction

NIOS Class 10 Science Chapter 24 Question Answers

INTEXT QUESTIONS 24.1

1. Define reproduction.

Ans: Biological process by which organisms give rise to offspring of their own kind.

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

Ans:

Asexual: Offspring produced by a single
Sexual: Two individuals are involved in producing offspring

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

Ans: A Cell divides to give rise to two offspring while losing its own identity

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

Ans: New plants may arise and grow from roots, stems, or leaves. e.g. Bryophyllum

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

Ans:

(i) Undifferentiated mass of cells in culture medium (callus)
(ii) Genetic copy of the parent, e.g,. Dolly – the cloned sheep.

INTEXT QUESTIONS 24.2

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

Ans: It serves as the reproductive organ of the plants.

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

Ans:

Self-pollination: When pollen from the same flower is deposited on the stigma and then fertilizes the ovule of the same flower.
Cross-pollination: Pollen from one flower falls on the stigma of another flower of the same species to fertilize the ovule of the latter.

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

Ans: Fertilisation leading to seed formation for the new generation of plants will not be possible.

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

Ans: Pollen grain forms a pollen tube, and the pollen grain nucleus reaches the ovule as the pollen tube pushes through the pistil. The pollen nucleus fuses with the nucleus of the ovule.

5. What is germination of seed?

Ans: Fertilized ovules develop into seeds, which are capable of germinating into seedlings and subsequently growing into new plants.

INTEXT QUESTIONS 24.3

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

(v) viviparous (vi) foetus

Ans:

(i) Stage of life at the age between 11 to 19 years when physical and physiological changes that take place in the body are called adolescence.
(ii) The time period during which changes occur that make humans capable of reproduction.
(iii) Both male and female sex organs are in the same individual.
(iv) Development of an embryo may occur to an extent or up to completion inside the egg.
(v) Babies develop inside the mother’s womb/ giving birth to young ones.
(vi) Developing embryo implanted in the uterus wall of the mother.

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

Ans: Testosterone and oestrogen

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

Ans: Testosterone and oestrogen

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

Ans:

(i) Embryo develops inside the uterus
(ii) Sperms pass through these into the ejaculatory duct

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 in many places on his body. His voice is croaky, and sometimes he has dreams that 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 his 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 places of worship during menstruation, and Madhu feels that she is being punished for something normal and definitely not her fault.

Based on your understanding of the 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.

Ans: Analysis of case studies attempted by students incorporating knowledge gained on adolescence and puberty.

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.

Ans: Write in your own words.

INTEXT QUESTIONS 24.4

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

Ans: Human sperm and Human ovum “formation of zygote “ developing embryo” foetus in the uterus, “born after development is complete”

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

Ans: FSH and LH

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

Hormones	Function

Ans:

Hormones	Function
FSH	Egg mature
LH	Egg shed
Estrogen	Secondary sexual characters in females
Testosterone	Secondary sexual characters in males
Oxytocin	Uterine contractions to deliver the baby

INTEXT QUESTIONS 24.5

1. Name any four sexually transmitted diseases.

Ans: Syphilis, Gonorrhea, herpes, Chlamydia

2. Name four devices which prevent fertilization in humans.

Ans: IUCD – Copper T, Oral contraceptive pills, vasectomy in male/tubectomy in female, MTP.

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

Ans:

(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?

Ans: Reproduction

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

Ans:

Asexual reproduction	Sexual Reproduction
Offspring are produced by a single individual.	Offspring are produced by two individuals
Will have the same genetic makeup	Genetic makeup different from parents

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

(i) Budding

(ii) Spore formation

(iii) Binary fission

(iv) Vegetative reproduction

Ans:

(i) Budding: Yeast
(ii) Spore formation: Chlamydomonas
(iii) Binary fission: Amoeba
(iv) Vegetative reproduction: Lawn grass

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

Ans: In vegetative reproduction, new plants are formed from roots, stems, leaves, or when a stem grows to a distance and then enters the soil and strikes roots to form a new plant As this process involves a single individual to produce new plants, this is called an asexual reproduction.

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

(i) Ginger

(ii) Grass

(iii) Onion

(iv) Potato

Ans:

(i) Ginger: Rhizome
(ii) Grass: Runner
(iii) Onion: Bulb
(iv) Potato: Tuber

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

Ans: In natural vegetative propagation, the stem naturally grows to a distance and enters or touches the soil, and grows roots. This can be separated into individual plants.

In artificial vegetative propagation, farmers manipulate the stem and bend it to touch the soil, allowing it to grow roots, and then separate the plants into individual units. Farmers and nursery owners multiply desired plants using the method of artificial propagation.

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

Ans: Callus is formed from a piece of plant, like a root or a leaf, and is grown in an adequate nutrient solution to form an undifferentiated mass of cells. This mass os cells is called the callus. This callus will later give rise to new plantlets. To make a callus,

The plant part is selected.
The cell is taken out of it
Transferred into a nutrient solution with hormones
Callus is formed.

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

Ans: All cells of an individual arise from a single cell, the zygote, and hence all cells have the same genes. Genes control growth, development, and all the life processes. This is why every living cell is considered totipotent.

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.

Ans:

(i) part that produces pollen: Stamens
(ii) part of the flower that receives the pollen: Stigma
(iii) part that contains ovules: Pistil
(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) Humans are ‘Viviparous’.

(iii) Earthworm is a ‘hermaphrodite’.

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

Ans:

(i) Birds, reptiles, and frogs are called ‘Oviparous’ because they lay eggs.
(ii) Humans are ‘Viviparous’ because the baby develops inside the mother’s womb.
(iii) Earthworm is a ‘hermaphrodite’ as both the female and male sex organs are in the same individual.
(iv) The sheep ‘Dolly’ was a clone of her mother because she was an exact copy of her mother and was produced through tissue culture.

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

Ans: Events after pollination.

Each pollen grain forms a pollen tube.
The pollen grain nucleus reaches the ovule as the pollen tube pushes through the pistil
Male and female gametes fuse to form the zygote.
The fertilized ovules develop into seeds, which are capable of germinating into seedlings and new plants

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 the testis and later join together to form an ejaculatory duct.

Ans:

Reproductive Organ of Human	Function
1. Testes	1) Produces the hormone Testosterone
2. Uterus	2) The womb in which the embryo develops
3. Cervix	3) Opening of the uterus
4. Vas deferens	4) Arise from the testis and later join together to form an ejaculatory duct.

13. List the physiological changes that arise at puberty in

Human female
Human male

Ans:

Human female	Human male
Girls develop a high-pitched voice	Boys develop a deep voice
Breast development in girls	Facial hairs grow in boys
Ovaries produce oestrogen	Testes produce progesterone

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

Ans: Mental, emotional, and intellectual maturity develops gradually:

Adolescents are capable of abstract thinking.
They experience mood swings.
They become self-conscious.
Self-image and identity become important.
Friendship is very important to them.
They start getting interested in one another in a sexual way.
Opinions expressed by peer that are different from their personal beliefs could be a source of stress and anxiety, as they need to fit in with the group norms

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

Ans: If there is no fertilization, the thickened lining of the uterus and blood vessels are shed off and cause bleeding. This is called menstruation and is also known as a period.

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

Ans: Write in your own words.

17. Why is it that –

(i) Women acquire STIs more easily as compared to men.

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

Ans:

Women acquire STIs more easily, as the disease-causing organisms can stay inside the vagina for a longer time.
Young women are more susceptible to acquiring STDs as their vaginal mucosa is immature.