Biology Class 12 Most Important Questions for NEET 2023

Chapter 1 - Reproduction in OrganismsChapter 1 - Reproduction in Organisms

Biology Class 12 Most Important Questions for NEET 2023

Chapter 1 - Reproduction in OrganismsChapter 1 - Reproduction in Organisms
Important Questions for NEET 2023

Q-1
Why is reproduction necessary for living beings?

Ans.
Reproduction is a fundamental characteristic of all living organisms. It is a biological process by which living organisms produce offspring similar to themselves. Reproduction ensures the continuation of various species on earth. In the absence of reproduction, the species would not be able to survive for long and could soon become extinct.

Q-2
Which is a better method of reproduction sexual or asexual? Why?

Ans.
Sexual reproduction is a better method of reproduction. This allows the formation of new forms by combining the DNA of two different individuals, usually one of each sex. It involves the fusion of male and female gametes, producing variants that are not identical to their parents and to themselves. This variation allows the individual to adapt to a constantly changing and challenging environment. Also, it leads to the evolution of better adapted organisms which ensures greater survival of a species. In contrast, asexual reproduction allows little or no variation at all. As a result, the individuals produced are exact copies of their parents and themselves.

Biology Class 12 Most Important Questions for NEET 2023

Q-3
Why is the offspring produced by asexual reproduction called clones?

Ans.
A clone is a group of morphologically and genetically identical individuals.

In the process of asexual reproduction, only one parent is involved and there is no fusion of male and female gametes. As a result, the offspring thus produced are morphologically and genetically identical to their parents and thus, are called clones.

Q-4
The offspring produced due to sexual reproduction have better chances of survival. Why? Is this statement always true?

Ans.
In sexual reproduction, there is a fusion of male and female gametes. This fusion allows the formation of new forms by combining the DNA of two (usually) different species members. Variations enable individuals to adapt to different environmental conditions for a better chance of survival.

However, it is not always necessary that the offspring produced due to sexual reproduction have better chances of survival. Under certain circumstances, asexual reproduction is more beneficial for some organisms. For example, some individuals do not move from place to place and are well-settled in their environment. Also, asexual reproduction is a fast and quick method of reproduction that does not consume as much time and energy as compared to sexual reproduction.

Q-6
Higher organisms have resorted to sexual reproduction despite its complexity. Why?

Ans.
Although sexual reproduction takes more time and energy, higher organisms have resorted to sexual reproduction despite its complexity. This is because this method of reproduction helps to introduce new changes in the offspring through combining the DNA of two (usually) different individuals. These variations allow the individual to face different environmental conditions and thus make the organism better adapted to the environment. Variations also lead to the evolution of better organisms and hence, provide better chances of survival. On the other hand, asexual reproduction does not provide genetic differences in the individuals produced.

Q-7
Explain why meiosis and gametogenesis are always interrelated.

Ans.
Meiosis is a process of reductional division in which the amount of genetic material is reduced. Gametogenesis is the process of formation of gametes. The gametes produced by organisms are haploid (containing only one set of chromosomes), while the body of the organism is diploid. Therefore, for the production of haploid gametes (gametogenesis), the germ cells of the organism undergo meiosis. During this process, an organism’s meiosis undergoes two consecutive nuclear and cell divisions, with one cycle of DNA replication forming haploid gametes.

Q-8
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 gametes ………………

(f) zygote ………………

Ans.
(a) Ovary diploid (2n)

(b) anther diploid (2n)

(c) Egg haploid (n)

(d) pollen haploid (n)

(e) male gamete haploid (n)

(f) zygote diploid (2n)

Q-9
Define external fertilization. Mention its disadvantages.

Ans.
External fertilization is the process in which the fusion of male and female gametes occurs outside the female body in an external medium, usually water. Fish, frogs, and starfish are some of the animals that exhibit external fertilization.

Disadvantages of external fertilization

In external fertilization, the chances of fertilization of the eggs are less. This may lead to wastage of large number of eggs produced during the process.

In addition, there is a lack of proper parental care of the offspring, resulting in low survival rates in the offspring.

Q-10
Describe the post-fertilization changes in a flower.

Ans.
Fertilization is the process of the fusion of the male and the female gamete to form a diploid zygote. After fertilization, the zygote divides several times to form an embryo. The fertilized ovule forms a seed. The seed contains an embryo, enclosed in a protective covering, called the seed coat. As the seed grows further, other floral parts wither and fall off. This leads to the growth of the ovary, which enlarges and ripens to become a fruit with a thick wall called the pericarp.

Q-11
What is a 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 the male and female reproductive structure (stamen and pistil) is called a bisexual flower. Examples of plants bearing bisexual flowers are

(1) Water lily (Nymphaea odorata)

(2) Rose (Rosa multiflora)

(3) Hibiscus (Hibiscus rosa-sinensis)

(4) Mustard (Brassica nigra)

(5) Petunia (Petunia hybrida)

Q-12
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.

Cucurbit plant bears unisexual flowers as these flowers have either the stamen or the pistil. The staminate flowers bear bright, yellow colored petals along with stamens that represent the male reproductive structure. On the other hand, the pistillate flowers bear only the pistil that represents the female reproductive structure.

Other examples of plants that bear unisexual flowers are corn, papaya, cucumber, etc.

Q-13
Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?

Ans.
Oviparous animals lay eggs outside their body. As a result, the eggs of these animals are under constant threat from various environmental factors. On the other hand, in viviparous animals, the development of the egg takes place inside the body of the female. Hence, the offspring of an egg-laying or oviparous animal is at greater risk as compared to the offspring of a viviparous animal, which gives birth to its young ones.

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