NCERT Solutions for Class 12 Biology Chapter 1

1. Why is reproduction essential for organisms?

Ans:  Reproduction is important for organisms due to the fact that by reproduction we will reproduce our younger ones who're much like us in a maximum of our characters. Reproduction allows us to keep the existence of species even after our death. This process also helps to create recombination by the process of meiosis. It is a source of genetic recombination.

2. Which is a better mode of reproduction sexual or asexual? Why?

Ans: Sexual reproduction is known to be a better way of reproduction found in organisms. This method is found to be better because it enables new variants to be formed by combining the DNA of two different individuals, typically one of each species. This means that it involves the fusion of gametes of both the individuals i.e male and female to produce zygotes. This variation which was developed in offspring enables them to adapt to changing and challenging environments. In addition, it leads to the development of adapted organisms that ensure greater survival of a species. Conversely, asexual reproduction allows little or no variation. As a result, the individuals who are produced are found to be exact copies of their parents and themselves.

3. Why is the offspring formed by asexual reproduction referred to as clones?

Ans: Clone is a word denoted to a group of genetically identical organisms. As we all know, that only a single parent is involved in asexual reproduction, the offspring which is produced is genetically identical to the parent cell. As we all know that they are exact copies of their parents, the offspring is said to be a clone. This type of reproduction can be seen in many prokaryotic organisms and even in a few eukaryotic single-celled and multi-celled organisms.

4.  Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?

Ans: Yes, offsprings that are produced via sexual reproduction tend to have better survival rates as compared to asexual reproduction. This is due to the fact that during sexual reproduction, the gametes of both of the parents, male and female, come together and fuse. Thus, the offspring carries the genetic material from both parents. This means that it involves the fusion of gametes of both the individuals i.e male and female to produce zygotes. This variation which was developed in offspring enables them to adapt to changing and challenging environments. In addition, it leads to the development of adapted organisms that ensure greater survival of a species.

5. How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?

Ans: The difference between progeny formed from asexual reproduction from those formed by sexual reproduction are as follows-

6. Distinguish asexual and sexual reproduction. Why is vegetative reproduction also considered a type of asexual reproduction?

Ans: The difference between asexual reproduction and sexual reproduction are as follows-

Vegetative  propagation

It is a type of process in which new plants are obtained without the production of sexual structures i.e seeds or spores. It involves the propagation of plants through different types of vegetative parts such as the rhizome, sucker, tuber, bulb, etc. In this, a fusion of the male and the female gamete does not take place and requires only one parent. Hence, vegetative reproduction can be stated under the category of asexual reproduction.

7. What is vegetative propagation? Give two suitable examples.

Ans: Vegetative propagation is defined as an asexual mode of reproduction in which new plants are obtained from the vegetative parts of the plant. It does not include the production of seeds or spores for new plants to propagate. Vegetative parts of plants include rhizomes, tubers, runners, etc. They can be used as reproductive organs to grow new plants. 

Some of the examples of vegetative propagation are:

• Eyes of potato:

The surface of the potato has many buds on it called eyes. Each of these eyes, when buried in the ground, becomes a new plant that is identical to the mother plant.

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• Leaf buds of Bryophyllum:

Bryophyllum plant leaves have multiple adventitious buds on their edges. These shoots have the ability to grow into tiny plants when the leaves break off the plant and come in contact with moist soil.

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8. Define-

a.  Juvenile phase.

Ans: The juvenile phase of an organism's life is described as the time of growth that begins after birth and ends before it achieves reproductive maturity. It is often termed the vegetative phase.

b. Reproductive phase.

Ans: The reproductive phase is defined as the period when an individual organism is sexually active and attains reproductive maturity. In this phase, the production of gametes also takes place.

c. Senescent phase.

Ans: The senescence phase is the time after the reproductive phase when a cell loses its ability to reproduce. Here the cell can grow old and stop dividing, but it does not die. This is also known as cell ageing.

9. Higher organisms have resorted to sexual reproduction despite its complexity. Why?

Ans: Higher organisms have resorted to sexual replication even after having such complexity because offspring of sexual reproduction have variations in their genes which helps their survival. It helps organisms to adapt to the environment easily. This is due to the fact that during sexual reproduction, the gametes of both of the parents, male and female, come together and fuse. Thus, the offspring tends to have the genetic material or information carried from both parents. This means that it involves the fusion of gametes of both the individuals i.e male and female to produce zygotes. This variation which was developed in offspring enables them to adapt to changing and challenging environments.

10. Explain why meiosis and gametogenesis are always interlinked?

Ans: Meiosis is the process of cell division that reduces the number of chromosomes by half, and gametogenesis is the formation of male and female gametes. These two terms are often linked because gametes are only formed in diploid organisms through meiosis. Meiosis (reduced division) produces four gametes from a germ cell. Male and female gametes combine during fertilisation, resulting in a diploid zygote (i.e. with paired chromosomes).

11. Identify each part in a flowering plant and write whether it is haploid (n) or diploid (2n).

• Ovary …..

Ans: Ovary Diploid (2n).

• Anther …..

Ans: Anther Diploid (2n)

• Egg …..

Ans: Egg Haploid (n)

• Pollen…..

Ans: Pollen Haploid (n)

• Male gamete…..

Ans: Male gamete Haploid (n)

• Zygote…..

Ans: Zygote Diploid (2n)

12.  Define external fertilization. Mention its disadvantages.

Ans: External fertilization is defined as the process by which the fusion of the male and female gametes takes place outside the female body in an external environment, generally water. Animals that show external fertilization are fish, frogs, starfish, etc. External fertilization has certain disadvantages: external fertilization gives the eggs a lower chance of fertilization, which can result in large numbers of eggs being wasted during this process; In addition, there is a lack of adequate parental care for the offspring, resulting in a low survival rate in progress.

13. Differentiate between a zoospore and a zygote.

Ans: Difference between a zoospore and a zygote:-

14. Differentiate between gametogenesis from embryogenesis.

Ans: Difference between gametogenesis and embryogenesis:-

15. Describe the post-fertilization changes in a flower. 

Ans: 

• Fertilization is the process of the fusion of the male and the female gamete, which leads to the formation of a diploid zygote.

• Once fertilization takes place, the sepals, petals, and stamens of the flower wither and fall off. The pistil, however, stays connected to the plant. 

• The zygote then develops into the new part which is known as an embryo and the ovules change into the seed.

• The ovary develops into the fruit which develops a thick wail referred to as pericarp that is shielding in function. 

• In the end,  Ovule develops into seed and ovary into fruit.

16. What is the bisexual flower? Collect five bisexual flowers from your neighborhood and with the help of your teacher find out their common and scientific names. 

Ans: A flower that contains both of the reproductive structures i.e the male and female reproductive structure (stamen and pistil) is called a bisexual flower. Examples of plants which bisexual flowers are:

• Water lily - scientific name -Nymphaea odorata 

• Rose - scientific name -Rosa multiflora 

• Hibiscus - scientific name -Hibiscus rosa-sinensis

• Mustard - scientific name -Brassica nigra

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?

Ans:

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The cucurbits have unisexual flowers. These types of flowers have stamen or pistil. Staminate flowers, for example, feature vivid yellow petals and stamens, which indicate the male reproductive mechanism. On the other hand, Pistilized flowers only have the pistil, which represents the female reproductive structure. If the fruit is visible in a fertilized female flower, it is very small and hardly visible. Other examples of plants that have unisexual flowers are papaya, corn, cucumber,  etc.

18. Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?

Ans: Egg-laying animals which are commonly called oviparous lay eggs outside their bodies. Due to this reason, the eggs of these animals are constantly threatened by various environmental factors. On the other hand in viviparous animals, the development of the egg takes place within the body of the female. protects the embryo or fetus from predators. Therefore, the offspring of an egg-laying or egg-laying animal are at greater risk than the offspring of a viviparous animal that gives birth to its young.

Reproduction in Organisms Class 12 NCERT PDF

The solutions of Biology Class 12, chapter 1 are prepared in a free PDF format. By downloading and studying from these solutions, you will be able to clear doubts and have the confidence to tackle the 12th board exam.

NCERT Solutions for Class 12 Biology Chapter 1 Reproduction in Organisms

This Biology NCERT solution contains 18 key questions from the chapter Reproduction in Organisms, and here is a brief discussion. Take a look!

• Reproduction in Organism’s Class 12 NCERT Solutions: Question 1

In the first question, students need to discuss how essential reproduction is to continue an organism’s generation. You can also put more light on the three different life phases. Without reproduction, there will be no existence of life on the planet.

• Reproduction in Organism’s Class 12 NCERT Solutions: Question 2

In the second question, you will have to write the comparison between sexual and asexual reproduction, and state which mode is better by providing relevant justification.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 3

This question asks students the reason why offspring produced from asexual reproduction is referred to as a clone.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 4

In this question, you need to write about why sexual reproduction is considered a better mode of reproduction. The child produced by sexual reproduction has maximum chances of survival.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 5

Biology Class 12 chapter 1 question 5 is about the difference between progeny formed asexual and sexual reproduction.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 6

This question asks students to distinguish between asexual and sexual reproduction, and why vegetative reproduction falls under the category of asexual reproduction.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 7

In this question, you will have to write about vegetative propagation and support your answer with examples like:

Diagram showing the eyes of a potato

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• Reproduction in Organism's Class 12 NCERT Solutions: Question 8

This question is about defining juvenile phase, reproduction phase and senescent phase.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 9

Question 9 asks students to write why higher organisms use the sexual reproduction method, though being complex.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 10

This question requires an explanation about the link between meiosis and gametogenesis.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 11

In this question, students will have to identify the parts of flowering plants and mention whether they are diploid or haploid.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 12

Biology Class 12 chapter 1 question 12 requires the definition of external fertilisation and the disadvantages of the same.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 13 and 14

These two questions ask the differences between zygote and zoospore, and gametogenesis and embryogenesis, respectively.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 15

Here, students will have to describe the changes that take place during post-fertilisation in flower.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 16

This question is about the explanation of bisexual flowers, and asks the learners to collect five bisexual flowers from their surrounding areas, and seek for their scientific and common names.

• Reproduction in Organism's Class 12 NCERT Solutions: Question 17

Question 17 asks the students to inspect flowers of a cucurbit plant and rule out the pistillate and staminate flowers. 

• Reproduction in Organism's Class 12 NCERT Solutions: Question 18

In the final question, you will have to write why the offspring of viviparous animals have less risk than the offspring of oviparous animals.

Biology Class 12 Chapter 1: Marks Weightage

Reproduction in organisms is the first chapter of Unit 1 from CBSE Biology book. A total of 12 marks is set for this unit in 12th board exams, but segregation of marks for each chapter is not defined.

Class 12 Biology Chapter 1 NCERT Solutions Benefit

Take a look at some of the benefits of the NCERT solution of Class 12 Biology chapter 1 in preparation of board exams:

1. Use of simple language, such that everyone can easily comprehend them.

2. Solutions are written by some of the experienced faculty members.

3. A considerable amount of materials for practising.

4. Emphasis on complex topics and concepts.

Hence, it is always profitable to make use of the NCERT solutions to refrain from struggling with the questions in board exams. Download the NCERT solutions of Class 12 Biology chapter 1 PDF offered by Vedantu today!