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Class 12 Biology – Reproduction in Organisms
In this chapter, we will look into Class 12 Biology Reproduction in Organisms. The chapter, in general, besides providing a basic background of understanding the process of reproduction in various organisms, gives insights into the mechanisms and functions involved in this very essential biological process.
Class 12 Biology Reproduction in Organisms refers to the process by which living organisms produce offspring or new individuals of the same species. It is a very important aspect of life, since through this, the continuity and survival of species for generations are assured. Reproduction can either be sexual or asexual, depending on the organisms involved and their nature.
Important Questions on Class 12 Biology – Reproduction in Organisms
1) Why does the number of male gametes produced by Bryophytes and Pteridophytes are comparatively more than the number of female gametes?
Ans – The male gametes require water to reach the female gametes increasing their chance of getting lost in the process leading to the increasing production of male gametes by Bryophytes and Pteridophytes compared to the female gametes.
2) The transformation of the mountain regions in Kerala, Karnataka, and Tamil Nadu into blue stretches is what become the leading tourist attraction. Explain.
Ans – Strobilanthus kunthiana is the plant, bearing flowers only once in 12 years. This flower bloomed in the year 2006 and caused the transformation of the hilly areas of Kerala, Karnataka, and Tamil Nadu into blue stretches.
3) What are the ‘oestrus cycle’ & ‘menstrual cycle’?
Ans –
Oestrus cycle – This cycle results in the female being fertile and sexually responsive along with the relatable rise in body temperature or as claimed “being in heat”. This cycle in the cows lasts for 21 days.
Menstrual cycle – This cycle affects the female leading to more complex steps depending upon the hormonal changes that occur in the body of the primates. The period of this cycle is 28 days.
4) State the differences between gametogenesis & embryogenesis.
Ans – The differences between gametogenesis & embryogenesis are stated below:
| Gametogenesis | Embryogenesis |
|---|---|
| The diploid or haploid precursor cells evolve into mature haploid gametes. | It is the emergence of a detailed embryo. |
| Male and female gametes are developed. | The embryo is developed resulting in the formation of the zygote. |
| In animals, the location is the testes and ovaries, where it occurs. In the case of plants, it is the antheridia and archegonia. | It occurs in the female reproductive system in animals and the female gametophyte in plants. |
5) In the process of sexual reproduction, syngamy is a significant event. Give reason.
Ans – Syngamy is the fusion process between the male and female gametes during fertilization, guaranteeing the reproduction ability of organisms to elongate their hierarchy. This process eventually leads to the formation of a diploid zygote or embryo by amalgamation of the egg nucleus with the male gamete.
6) Explain the process of embryogenesis.
Ans – The process in which an egg cell undergoes fertilization by a sperm cell and results in the ovum becoming a zygote, a single diploid cell is known as embryonic development. The process in which the embryo of an animal or plant develops is called embryogenesis.
7) a. Difference between asexual reproduction and sexual reproduction. Proof that vegetative reproduction is a branch of asexual reproduction.
Ans – The differences between asexual reproduction and sexual reproduction are as follows:
| Asexual Reproduction | Sexual Reproduction |
|---|---|
| It involves only one parent. | It involves two parents. |
| Gametes have no set of participation in this process. | Gametes have any in this process. |
| Occurrence of only miotic division. | Occurrence of meiosis (during gamete formation) and mitosis (during fertilization). |
| Progeny is necessarily the same as the parent. | Progeny varies humongous from the parents. |
When the progeny arises from the vegetative part of the parent and resembles the parent, this process is called vegetative propagation.
b. Is the sexual mode of reproduction better than the asexual mode of reproduction?
Ans – Yes. The sexual mode of reproduction is better than the asexual mode of reproduction and the reasons are as follows:
- Offsprings have their variations.
- Capabilities of the offspring to tolerate extreme weather multiplies.
- Amalgamation of two parents results in the insertion of both their traits in the progeny.
8) Distinguish between the offspring produced by asexual reproduction and progeny produced by sexual reproduction.
Ans – In the consideration of the genetic constitution, offspring produced by asexual reproduction are similar by genetics whereas progeny produced by sexual reproduction varies by genetics.
Why is Reproduction Important in Organism?
It is very essential for species survival and evolution. Reproduction allows the transfer of genetic material from generation to generation, hence ensuring its diversity and adaptability. In this way, through reproduction, organisms manage to adapt to changing environments and avoid extinction. NCERT chapter is available in PDF format.