Class 12 biology chapter 1 questions and answers

Class 12 biology chapter 1 notes

NCERT class 12 biology chapter 1 “Reproduction in Organisms” covers the different modes of Reproduction in organisms, including asexual and sexual reproduction, and the mechanisms involved in these processes.

Introduction to reproduction:

The chapter begins by introducing the concept of reproduction and defines it as the process by which organisms produce new individuals of the same kind. This process is essential for the continuation of a species and the continuation of life on earth.

Asexual reproduction:

The chapter describes the two main types of reproduction: asexual and sexual reproduction. Asexual Reproduction is a process by which an organism produces offspring without the involvement of sex cells. The various modes of asexual reproduction are binary fission, fragmentation, budding, and vegetative propagation.

– Binary fission is a process of cell division in which a single cell divides into two identical daughter cells. This is common in prokaryotic organisms such as bacteria.

– Fragmentation is a process in which an organism breaks into two or more pieces and each piece develops into a new individual. This is common in some invertebrates such as flatworms.

– Budding is a process in which a small outgrowth or bud develops on the parent organism, which eventually separates and develops into a new individual. This is common in some invertebrates such as Hydra and Yeast.

– Vegetative propagation is a process in which new plants are produced from the vegetative parts of the parent plant such as roots, stem, and leaves. This is common in plants such as strawberry, grass, and ginger.

Asexual reproduction has the advantage of producing genetically identical offspring and the ability to reproduce quickly in favorable conditions. But it has the disadvantage of producing no genetic diversity and no adaptation to changing environments.

Sexual reproduction:

The chapter explains the process of sexual reproduction, including the stages of meiosis, fertilization, and zygote formation.

– Meiosis is a process of cell division that reduces the number of chromosomes in a cell by half. This process occurs in the gonads (testes and ovaries) of animals and in the anthers and ovules of plants. It produces four genetically different cells, called haploid cells, which will eventually develop into sperm or eggs.

– Fertilization is the process of combining the genetic material from the male and female gametes to form a zygote.

– The zygote is the first cell of a new organism and contains the complete set of genetic information.

Sexual reproduction has the advantage of producing genetically diverse offspring and the ability to adapt to changing environments. But it has the disadvantage of taking longer to reproduce and the need for two individuals to reproduce.

Male and female reproductive systems:

The chapter covers the differences between the male and female reproductive systems and the process of gamete production. It explains the structure and function of the different parts of the male and female reproductive systems and how they contribute to the process of reproduction.

The male reproductive system includes the testes, epididymis, vas deferens, prostate gland, and urethra. The testes produce sperm and testosterone, the epididymis stores and transports sperm, the vas deferens carries sperm from the epididymis to the urethra, the prostate gland produces a fluid that helps to nourish and transport the sperm, and the urethra carries both urine and semen out of the body.

The female reproductive system includes the ovaries, fallopian tubes, uterus, cervix, and vagina. The ovaries produce eggs and hormones, the fallopian tubes transport eggs from the ovaries to the uterus, the uterus is the site of fertilization and fetal development, the cervix is the lower part of the uterus that opens into the vagina, and the vagina is the canal that leads to the outside of the body.

Significance of reproduction:

The significance of reproduction in the survival and evolution of organisms is an important topic in the field of biology, as it helps to ensure the continuation of a species over time. Reproduction is the process by which organisms create descendants, either through asexual or sexual means. The advantages and disadvantages of both asexual and sexual reproduction are discussed in the chapter, with asexual reproduction being efficient and rapid, but lacking genetic diversity, while sexual reproduction is less efficient but allows for the mixing of genetic material and the creation of new genetic combinations.

The various mechanisms that have evolved to ensure successful reproduction are also discussed in the chapter, including the role of hormones and other signaling molecules in the regulation of reproduction, as well as the physical structures and behaviors that have evolved to aid in reproduction.

The chapter concludes by discussing the different reproductive strategies adopted by organisms, including reproduction in unicellular and multicellular organisms. Unicellular organisms, such as bacteria and protozoa, typically reproduce through a process called binary fission, where a single cell divides into two identical daughter cells. Multicellular organisms, on the other hand, often reproduce sexually, with the formation of specialized reproductive cells called gametes.

Class 12 biology chapter 1 NCERT questions and answers

QUESTIONS:

1. Why is reproduction essential for organisms?
2. Which is a better mode of reproduction: sexual or asexual? Why?
3. Why is the offspring formed by asexual reproduction referred to as clone?
4. Offspring formed due to sexual reproduction have better chances of
survival. Why? Is this statement always true?
5. How does the progeny formed from asexual reproduction differ from
those formed by sexual reproduction?
6. Distinguish between asexual and sexual reproduction. Why is vegetative
reproduction also considered as a type of asexual reproduction?

7. What is vegetative propagation? Give two suitable examples.
8. Define
(a) Juvenile phase,
(b) Reproductive phase,
(c) Senescent phase.
9. Higher organisms have resorted to sexual reproduction in spite of its
complexity. Why?
10. Explain why meiosis and gametogenesis are always interlinked?
11. Identify each part in a flowering plant and write whether it is haploid
(n) or diploid (2n).
(a) Ovary ———————————
(b) Anther ———————————
(c) Egg ———————————
(d) Pollen ———————————
(e) Male gamete ———————————
(f) Zygote ———————————
12. Define external fertilisation. Mention its disadvantages.
13. Differentiate between a zoospore and a zygote.
14. Differentiate between gametogenesis from embryogenesis.
15. Describe the post-fertilisation changes in a flower.
16. What is a bisexual flower? Collect five bisexual flowers from your
neighbourhood and with the help of your teacher find out their common
and scientific names.
17. Examine a few flowers of any cucurbit plant and try to identify the
staminate and pistillate flowers. Do you know any other plant that
bears unisexual flowers?
18. Why are offspring of oviparous animals at a greater risk as compared
to offspring of viviparous animals?

ANSWERS

1. Reproduction is essential for organisms because it allows for the continuation of the species and preservation of genetic information.
2. The superiority of either sexual or asexual reproduction depends on the specific context and the organism’s environment. Sexual reproduction can promote genetic diversity, but asexual reproduction can result in faster growth and colonization of new habitats.
3. Offspring formed by asexual reproduction are referred to as clones because they are genetically identical to the parent organism.
4. The statement that offspring formed due to sexual reproduction have better chances of survival is not always true. Genetic diversity through sexual reproduction can provide benefits, but it also introduces new genetic mutations that can be harmful.
5. The progeny formed from asexual reproduction are genetically identical to the parent organism, while offspring formed by sexual reproduction have a mix of genetic information from both parents.
6. Asexual reproduction involves the production of offspring without the involvement of gametes or sexual reproduction, while sexual reproduction involves the fusion of gametes. Vegetative reproduction is considered a type of asexual reproduction because it involves the growth of new individuals from vegetative organs, such as roots or leaves, without the involvement of gametes.
7. Vegetative propagation is a type of asexual reproduction that involves the growth of new individuals from vegetative organs, such as roots or leaves. Examples include propagation by cuttings and layering.
8. (a) Juvenile phase refers to the developmental stage when an organism is not yet sexually mature. (b) Reproductive phase refers to the stage of an organism’s life when it is capable of producing offspring. (c) Senescent phase refers to the later stage of an organism’s life when its reproductive capacity declines.
9. Higher organisms have resorted to sexual reproduction despite its complexity because it promotes genetic diversity and adaptability, which can increase the survival of offspring in changing environments.
10. Meiosis and gametogenesis are always interlinked because meiosis is the process of cell division that results in the formation of gametes, which are the cells involved in sexual reproduction.
11. (a) Ovary – 2n (b) Anther – n (c) Egg – n (d) Pollen – n (e) Male gamete – n (f) Zygote – 2n
12. External fertilization is the process of fertilization that occurs outside of the body of the female organism. Disadvantages include increased vulnerability of eggs or sperm to predation and environmental factors.
13. A zoospore is a single-celled, flagellated spore produced by some algae and fungi through asexual reproduction. A zygote is a cell that is formed by the fusion of two gametes during sexual reproduction.
14. Gametogenesis involves the formation of gametes, while embryogenesis involves the development of the zygote into a multicellular organism.
15. Post-fertilization changes in a flower include growth of the ovary into a fruit and formation of seeds.
16. A bisexual flower is a flower that has both male and female reproductive organs. Examples include sunflowers and roses.
17. A cucurbit plant bears both staminate and pistillate flowers, with staminate flowers containing only male reproductive organs and pistillate flowers containing only female reproductive organs. Another example of a plant that bears unisexual flowers is the corn plant.
18. Offspring of oviparous animals are at a greater risk than those of viviparous animals because eggs are more vulnerable to predation and environmental factors compared to those that develop within the female’s body.

Class 12 biology chapter 1 Extra question answers:

1. Define reproduction. Reproduction is the biological process by which organisms create descendants.
2. What is asexual reproduction? Asexual reproduction is a type of reproduction that occurs without the fusion of gametes or involvement of meiosis.
3. What is sexual reproduction? Sexual reproduction is a type of reproduction that involves the fusion of gametes from two individuals to form a new individual.
4. What is the significance of reproduction? Reproduction is essential for the continuation of species and genetic diversity.
5. What is fragmentation? Fragmentation is a type of asexual reproduction where an organism is separated into fragments, which then grow into mature individuals.
6. What is budding? Budding is a type of asexual reproduction where a new individual develops as an outgrowth from an existing organism.
7. What is regeneration? Regeneration is the ability of an organism to regrow lost or damaged body parts.
8. What is vegetative propagation? Vegetative propagation is the process of producing new plants from existing ones, without the involvement of seeds or spores.
9. What is parthenogenesis? Parthenogenesis is a type of asexual reproduction in which development of an offspring occurs from an unfertilized egg.
10. What is self-fertilization? Self-fertilization is the process of fertilization between gametes from the same individual.

11. What is the role of meiosis in sexual reproduction? Meiosis is a type of cell division that reduces the chromosome number by half, creating haploid cells for sexual reproduction. It is essential for creating genetic diversity in offspring.
12. What are the advantages of sexual reproduction? Advantages of sexual reproduction include creating genetic diversity, adapting to changing environments, and removing harmful mutations from the population.
13. What is the difference between sexual and asexual reproduction? Sexual reproduction involves the fusion of gametes from two individuals to form a new individual, while asexual reproduction occurs without the fusion of gametes.
14. What are the disadvantages of asexual reproduction? Disadvantages of asexual reproduction include the lack of genetic diversity, increased susceptibility to diseases and environmental changes, and reduced adaptability.
15. What is the importance of regeneration in organisms? Regeneration is important because it allows organisms to recover from injuries or damage, and it is an essential mechanism for survival in certain species.
16. What is the difference between vegetative propagation and grafting? Vegetative propagation is the process of producing new plants from existing ones, without the involvement of seeds or fragments. Grafting, on the other hand, is a horticultural technique where parts of two different plants are joined together to form a single entity.
17. What is the significance of parthenogenesis in plants and animals? Parthenogenesis is significant because it allows for the reproduction of offspring without the need for mating or fertilization. This can be advantageous in environments where partners are scarce or mating is difficult. What is the role of gametes in sexual reproduction? Gametes are specialized cells that carry genetic information and are involved in the fusion during fertilization to form a new individual in sexual reproduction.

18. What is the role of gametes in sexual reproduction? Gametes are specialized cells that carry genetic information and are involved in the fusion during fertilization to form a new individual in sexual reproduction.
19. What is the process of fertilization in sexual reproduction? Fertilization is the process of fusion of male and female gametes to form a zygote, which then develops into an offspring.
20. What is the role of gonads in reproduction? Gonads are the reproductive organs that produce gametes in an organism. In males, they produce sperm and in females, they produce ova or eggs.
21. What is the process of ovulation in females? Ovulation is the process by which a mature ovum or egg is released from the ovary into the fallopian tube, where it can be fertilized by sperm.
22. What is the role of hormones in reproduction? Hormones play a crucial role in regulating the reproductive system by controlling the development and function of the gonads, as well as the timing and initiation of ovulation, menstruation, and sperm production.
23. What is the importance of reproductive health? Reproductive health is important for ensuring the well-being of individuals and communities by promoting healthy sexual and reproductive behaviors, preventing and treating reproductive illnesses, and ensuring access to family planning services.
24. What is population growth and how is it affected by reproductive strategies? Population growth is the increase in the number of individuals in a population over time. It is affected by the reproductive strategies of a species, such as the frequency of mating, the number of offspring produced, and the survival rate of offspring.

Class 12 biology chapter 1 Multiple choice question answers:

1. What is the process of producing new individuals through the fusion of gametes called? a) Asexual reproduction b) Sexual reproduction c) Regeneration d) Vegetative propagation

Answer: b) Sexual reproduction

2. What type of reproduction occurs without the fusion of gametes? a) Sexual reproduction b) Asexual reproduction c) Regeneration d) Vegetative propagation

Answer: b) Asexual reproduction

3. What is the process of regrowing lost or damaged body parts called? a) Regeneration b) Vegetative propagation c) Asexual reproduction d) Sexual reproduction

Answer: a) Regeneration

4. What is the process of producing new plants from existing ones, without the involvement of seeds or fragments called? a) Vegetative propagation b) Regeneration c) Asexual reproduction d) Sexual reproduction

Answer: a) Vegetative propagation

5. What is the process of development of an offspring from an unfertilized egg called? a) Parthenogenesis b) Self-fertilization c) Fertilization d) Ovulation

Answer: a) Parthenogenesis

6. What is the process of fertilization between gametes from the same individual called? a) Parthenogenesis b) Self-fertilization c) Fertilization d) Ovulation

Answer: b) Self-fertilization

7. What are the reproductive organs that produce gametes in an organism? a) Gonads b) Ovaries c) Testes d) Both b and c

Answer: d) Both b and c

8. In which type of reproduction is the offspring produced with exactly the same genetic material as the parent? a) Sexual reproduction b) Asexual reproduction c) Regeneration d) Vegetative propagation

Answer: b) Asexual reproduction

9. What is the process of producing new individuals through the division of cells or fragmentation of the parent body called? a) Sexual reproduction b) Asexual reproduction c) Regeneration d) Vegetative propagation

Answer: b) Asexual reproduction

10. What is the process of producing new individuals from specialized reproductive structures or spores of the parent body? a) Sexual reproduction b) Asexual reproduction c) Regeneration d) Vegetative propagation

Answer: d) Vegetative propagation

11. What is the process of fusion of male and female gametes called? a) Fertilization b) Ovulation c) Parthenogenesis d) Self-fertilization

Answer: a) Fertilization

12. What is the process of releasing a mature ovum from the ovary into the fallopian tube called? a) Fertilization b) Ovulation c) Parthenogenesis d) Self-fertilization

Answer: b) Ovulation

13. What is the process of development of an offspring from a fertilized egg called? a) Fertilization b) Ovulation c) Parthenogenesis d) Embryogenesis

Answer: d) Embryogenesis

14. What is the role of hormones in the regulation of the reproductive system? a) Stimulating the development and function of the gonads b) Regulating the timing and initiation of ovulation, menstruation, and sperm production c) Both a and b d) None of the above

Answer: c) Both a and b.

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