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NCERT Solutions for Class 12 Biology Chapter 2 - Sexual Reproduction In Flowering Plants

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Last updated date: 17th Apr 2024
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NCERT Solutions for Class 12 Biology Chapter 2

NCERT Solutions for Class 12 Biology, Chapter 2, Sexual Reproduction In Flowering Plants is an imperative part of the syllabus to be prepared by class 12th students. Thus, the said solutions have been prepared to provide a proper study resource for Class 12 students. All the concepts covered in the chapter are thoroughly explained in these NCERT Solutions. Also, NCERT Solutions for Chapter 2 of Biology Class 12 have been prepared by subject experts who hold numerous years of teaching experience. Thus, students who are appearing for their board exams can refer to this resource for their exam preparation. The NCERT Solutions for Sexual Reproduction In Flowering Plants Class 12, provides a comprehensive study of the concepts covered in the chapter. Prepared by the expert teachers of Vedantu, CBSE NCERT Solutions for class 12 explains each and every concept in detail making you’re studying an easy process.


The students can get ample benefits by referring to these NCERT Solutions for doing their homework, assignments, and practice tests for their upcoming board examinations. 


Class:

NCERT Solutions for Class 12

Subject:

Class 12 Biology

Chapter Name:

Chapter 2 - Sexual Reproduction in Flowering Plants

Content-Type:

Text, Videos, Images and PDF Format

Academic Year:

2024-25

Medium:

English and Hindi

Available Materials:

  • Chapter Wise

  • Exercise Wise

Other Materials

  • Important Questions

  • Revision Notes



Sexual Reproduction in Flowering Plants Chapter at a Glance - Class 12 NCERT Solutions


Sexual Reproduction in Flowering Plants


Sexual Reproduction in Flowering Plants


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Access NCERT Solutions for Class 12 Biology Chapter 2- Sexual Reproduction in Flowering Plants

1. Name the parts of an angiosperm flower in which the development of male and female gametophytes takes place.

Ans: In pollen sacs of the anther, male gametophytes (microgametogenesis) develop up to the 2-celled stage. The nucellus of an ovule is where the gametophyte develops (megagametogenesis).

 

2. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events?

Ans: Microsporogenesis and megasporogenesis differ in the following ways:

 

Microsporogenesis

Megasporogenesis

The process by which microspore mother cells divide and produce pollen grains is known as microsporogenesis.


Megasporogenesis is the process by which megaspore mother cells are formed and differentiate into megaspores by meiosis.

Located within the pollen sac of the anthers.

It is present in the nucellus of the ovule.

A pollen grain produced by a microspore mother cell functions properly.

The megaspores have only one functional megaspore.

Results in the formation of pollen grains (male  gametophyte)

 

Resulting in the formation of embryo sacs (female gametophyte)

Microspore mother cells and megaspore mother cells are every diploid, as they have two sets of chromosomes.

The mother cells for megaspores and microspores enlarge and undergo meiosis in order to produce four haplotypic cells called megaspores and microspores, respectively.



3. Arrange the following terms in the correct developmental sequence: Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.

Ans: The sporogenous tissue is composed of a pollen mother cell, a microspore tetrad, pollen grains, and male gametes.


4. With a neat, labeled diagram, describe the parts of a typical angiosperm ovule.

Ans:


Structure of Angiosperm Ovule


An angiosperm ovary is capable of forming a small structure called an ovule. Nucellus, a multi-layered cellular tissue, develops as the ovule first appears on the placenta. Placentas are attached to ovules via a stalk known as a funicle. A funicle attaches to a placenta at the hilum. The hypodermal cells of the nucellus enlarge and transform into megaspore mother cells. One haploid cell undergoes meiosis to form an embryo sac (female gametophyte). The others do not develop. A pollen tube enters an ovule through a small opening called a micropyle, surrounded by one or two protective layers. Ovules consist of the nucellus and integuments of a fully developed embryo.


5. What is meant by monosporic development of female gametophytes?

Ans: The female gametophyte or embryo sac develops only from one of the four megaspores in many flowering plants. Degeneration occurs in the three remaining megaspores. The monosporic type of embryo sac formation is referred to as the monosporic type of embryo development.


6. A neat diagram explains the 7-celled, 8-nucleate nature of the female gametophyte.


Structure of Female Gametophyte


Ans: Three successive mitotic divisions form it in the megaspore nucleus (or female gametophyte). The nucleus itself divides into two nuclei which move to opposite poles to form two nuclei of the embryo sac. The 8-nucleate stage of the embryo sac is formed after two more sequential mitotic nuclear divisions. A typical female gametophyte or embryo sac is formed after the 8-nucleate stage. The antipodal and micropylar end of each of the eight nuclei comprises the six nuclei grouped. There are two synergids and an egg cell at the center of the egg apparatus. The polar nuclei are located within the large central cell of the embryo sac just below the egg apparatus. A typical female gametophyte comprises seven cells with eight nuclei as both polar nuclei are present within the same cell.


7. What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.

Ans: The anther and stigma of chasmogamous flowers are exposed for pollination. Cleistogamous flowers are incapable of cross-pollination. Therefore, only self-pollination is caused by these closed flowers. During the dehiscence process of cleistogamous flowers, anthers dehisce into closed flowers. As a result, pollen grains are exposed to stigma. Therefore, it is impossible for cross-pollination to occur, such as Oxalis and Viola.


8. Mention two strategies evolved to prevent self-pollination in flowers

Ans: An individual race's vigor and vitality are diminished by continuous self-pollination. In order to prevent self-pollination and to promote cross-pollination, flowering plants have developed many devices. Cross-pollination is most frequently ensured by dichogamy and self-sterility.

Dichogamy: Different maturation times for the anthers and stigmas prevent self-pollination.

Self-sterility (or self-incompatibility): pollen grains from some flowers do not germinate on their stigma due to the presence of self-sterility genes. Examples include tobacco and potatoes.


9. What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?

Ans: On its stigma, a flower that does not produce pollen grains is incompatible or self-sterile. This condition is called self-incompatibility or self-sterility. It is called pollination when pollen grains are transferred from the stigma to the anthers. As a result of this transference, seeds are formed. The process of self-pollination occurs when pollen grains are shed from the anther in the same flower to the stigma in the same flower. Some flowers, however, do not produce seeds when self-pollination occurs because they contain the same sterile gene on the pistil and pollen grain. Since pollen grains cannot germinate, male gametes cannot fertilize egg cells. This prevents the ovule from developing into a seed.


10. What is a bagging technique? How is it useful in a plant breeding program?

Ans: A bag of polythene butter paper, when applied to emasculated flowers (which are in the bud stage), prevents pollen contamination of its stigmas. Emasculated flowers can be removed from their buds and stuffed into a bag of butter paper before anthesis. A pre-sterilized brush is used for dusting the stigmas of mature emasculated flowers with pollen grains of desired male plants. Flowers are then re-bagged until the fruits are formed. Artificial hybridization uses this technique primarily. Plant breeders use this technique to prevent unwanted pollen grains from contaminating the stigma of flowers.


11. What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.

Ans: Vegetative fertilization is the formation of a triploid primary endosperm nucleus (PEN) by fusing the second male gamete with the two polar nuclei present in the central cell of the central cell. The embryo sac is where this process occurs. The micropylar end of the pollen tube enters the embryo sac after reaching the ovary. Once the pollen tube has penetrated, its tip ruptures, releasing two male gametes. To form the diploid zygote, the one male gamete fuses with the egg. Trichotomy is the method of creating a triploid endosperm by combining the two male gametes and the two polar nuclei, and this method is called syngamy. It is a process of double fertilization in which both events of fertilization coincide.


12. Why do you think the zygote is dormant for some time in a fertilized ovule?

Ans: Zygotes become embryos after resting for a while. Until some amount of endosperm forms, most zygotes remain dormant. Developing embryos need this nutrition to grow and develop properly.


13. Differentiate between:

(a) Hypocotyl and epicotyl;

(b) Coleoptile and coleorhiza;

(c) Integument and testa;

(d) Perisperm and pericarp.

Ans:

(a) Hypocotyl and Epicotyl;

Epicotyl

Hypocotyl

This is the part of the embryonal axis between plumule and cotyledon nodes.

The area between the cotyledonary node and radicle forms part of the embryonal axis.

When epicotyl 2 elongates during hypogeal germination, the soil retains the cotyledons.

Hypocotyls extend so that cotyledons emerge from the soil during epigeal germination.

Epicotyls have plumules at their terminal ends.

Hypocotyls have radicals at their terminal ends.

 

(b) Coleoptile and Coleorhiza;

  Coleoptile 

Coleorhiza

A foliar structure called the coleoptile surrounds the epicotyl and a leaf primordium.

Roots and their caps are enclosed in a sheath called a coleorhiza.

It protects the plumule during emergence from soil.

For the first leaf to appear, there is an opening at the end of the coleoptile. The coleorhiza is a solid structure.

 

Plumules are protected from the soil when they emerge from soil.

Radicles are not protected when they pass through the soil.

It grows much beyond the grain

After emergence from grain, it stops growing

Coleoptile after emergence from soil

Coleorhiza does not come out of the soil.

Germination occurs when the seed becomes green and begins to photosynthesize.

It remains nongreen

 

 

 (c) Integument and Testa;

Integument

Testa

The ovule is covered by this membrane.

In other words, it is the outer covering of a seed.

There are two or three layers, and it is thin.

It is layered and quite thick.

Live cells make up its structure.

Cells in it are no longer alive.

There are no sclereids.

Sclereids are found in abundance in cells.

The ovule produces it at the chalazal end.

The ovule outer integument is the source of the ovule structure.

The integument is pre fertilised.

Structures that develop postfertilization are called testa

 

(d) Perisperm and Pericarp.

Perisperm

Pericarp

It serves as the nucleus of the seed.

From the ovary wall develops a covering for the fruit.

Seeds contain it.

It is a component of fruit.

Usually, it is dry.

There is no moisture or flesh in it.

Many times, seeds do not function properly.

Protection and nutrition are also provided by this covering.

Seeds without perisperm are rare.

Every fruit contains this.

 

14. Why is an apple called a false fruit? Which part(s) of the flower forms the fruit?

Ans: True fruit is an ovary that has ripened botanically. Often called false fruits, these are fruits in which the thalamus, floral parts, and ovary are present—apples, strawberries, cashews, etc. Mainly the fleshy thalamus of apples can be eaten—the ovaries from a parthenocarpic fruit after or without fertilization.


15. What is meant by emasculation? When and why does a plant breeder employ this technique?

Ans: The stem of a flower bud is systematically excised to remove the anthers and stamens before they die. In order to minimize self-pollination, this is done. Hybridization by artificial means includes emasculation. This method is used by plant breeders to prevent the pollination of adjacent flowers and pollinate stigmas with pollen of the desired variety.


16. If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?

Ans: The fruit of the parthenocarpy is seedless. The ovary does not fertilize them before they develop. A few seedless fruits are of great economic importance, such as banana, grape, orange, pineapple, guava, watermelon, and lemon. In fruits with edible seeds or seeds (e.g., pomegranates), parthenocarpy is not selected.


17. Explain the role of tapetum in the formation of pollen-grain walls.

Ans: Microsporangia are surrounded by a thin layer called the tapetum. Multinucleated and polyploidy tapetal cells make up the tissue. Pollen grains develop as a result of them. Ubisch bodies are found in these cells and contribute to the ornamentation of the microspores and pollen grains. Sporopollenin is a substance produced by the Ubisch bodies of the tapetal cells. This substance is present on the exine layer of pollen grains. A spiny appearance is attributed to the exine of pollen grains due to the presence of this compound.


18. What is apomixis and what is its importance?

Ans: The asexual reproduction process of apomixis results in seeds without fertilization, such as in certain species of Asteraceae and Grasses. The hybrid seed industry relies on this method. Increasing productivity is the leading reason for cultivating hybrids. However, the main problem is the need to grow hybrid seeds annually since seeds from hybrid plants do not preserve hybrid characteristics for long periods because of the segregation of characters. By introducing apomixis into hybrid seeds, this can be avoided. As a result, scientists are seeking genes associated with apomixis.



NCERT Solutions for Class 12 Biology Chapter 2 - Sexual Reproduction in Flowering Plants

Students who are preparing for their 12th board exams need an elaborate and detailed resource that can help them in getting a clear picture of the topics covered in their syllabus. However, since Biology chapters are vast, students need resources that can be their perfect guide to not only understand the topics, whether complex or easy but also to pass the exams with flying colours. Thus, PDF for NCERT Solutions for Class 12 Biology Chapter 2 is regarded as an exemplary resource for the exam preparation. The PDF is brilliantly prepared to walk the students of Class 12 through the diverse topics covered in the chapter. 


NCERT Solutions For Class 12 Biology Chapter 2 Sexual Reproduction In Flowering Plants

The NCERT Solutions for Class 12 Biology Chapter 2, Sexual Reproduction In Flowering Plants, assists students to familiarize themselves with the process of reproduction in flowers. Reproduction is the process of multiplication of a particular species, and there are two modes of reproduction for every living being: asexual and sexual. The flowers also have a basic sexual reproduction process that has been explained in detail in the NCERT Solutions for Chapter 2 of Class 12 Biology. 


Flowering plants portray the sexual method of reproduction and lead to the production of pollen and ova. The angiosperm consists of four different whorls of the floral appendages that are connected to the flower's receptacle. These whorls are corolla, calyx, gynoecium, and androecium. The chapter further explains the pre-fertilization process of the flower's sexual reproduction.


Class 12th Biology Chapter 2 NCERT Solutions further help the students in getting to know about the expected questions that can be asked in the board examinations. In addition to giving an idea about the type of questions to be asked in the exams, these NCERT Solutions also help the students to learn about the right way to answer the questions. Hence, by going through these solutions thoroughly, students can secure good marks in the examination. 


NCERT Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants is an important chapter for CBSE Class 12 Board Examination. Students can learn about the process involved in the formation of male and female gametes and their role in the production of a new plant in this chapter. Topics such as pollination, pre-fertilization events, post-fertilization events, and fusion of male and female gametes are some of the important concepts which are explained in a detailed manner in this chapter.


Chapter 2 of NCERT Class 12 Biology focuses on the different parts of a flowering plant, along with the formation process and reproduction. Students will also be familiar with the process of pollination in flowering plants where the pollen grains are transferred from one flower to another. In this chapter, pollination is explained clearly, with detailed illustrations of different forms of pollination, pollinating agents, and so on.


The list of topics covered under NCERT Class 12 Biology Chapter 2 is provided in the table below.

NCERT Class 12 Biology Chapter 2 Topics

Morphology and Anatomy of flowering plants

Pre-fertilization Events, Structure and Process

Double Fertilization

Post-fertilization

Apomixis 

Polyembryony


Benefits of NCERT Solutions For Class 12 Biology Chapter 2 Sexual Reproduction In Flowering Plants

Sexual Reproduction In Flowering Plants, Class 12, NCERT Solutions is a compilation of effective resources for studying the chapter effectively. Here are some of the benefits of the chapter.

  • The students can download the PDF on their laptops or computers and can even get them printed for studying without internet connectivity.

  • Subject experts have explained the different concepts covered in this chapter in an easily understandable manner for the convenience of students.

  • All types of textbook questions and exercises are solved and explained in the NCERT Solutions PDF.


NCERT Class 12 Biology Chapter wise Solutions - Free PDF Download

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NCERT Solutions Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants - Key Features

  • The NCERT Solutions have been developed as per the prescribed CBSE Term 1 syllabus.

  • The solutions provided come with simple and well-structured explanations to aid easy understanding.

  • Labelled diagrams have been supplemented with explanations to facilitate easy grasping of the concepts.

  • The solutions have been designed with the purpose of enhancing the students’ conceptual knowledge of sexual reproduction in flower plants.

  • The Biology experts have taken proper care in curating the solutions keeping in mind the latest CBSE Class 12 protocols.

  • These NCERT Solutions of Biology will also be very helpful and effective for NEET aspirants and other entrance exams.

FAQs on NCERT Solutions for Class 12 Biology Chapter 2 - Sexual Reproduction In Flowering Plants

1. If a person can induce the process of parthenocarpy through growth substances, which fruits need to be selected?

The parthenocarpy fruits are seedless, and they can be easily developed from the plant's ovary without undergoing fertilization. Thus, one can use grapes, bananas, lemon, pineapple, and guava are the fruits that can be used for the said process. These fruits are seedless and considered to be economical fruits developed through the said process. The technique of parthenocarpy includes the principle of inducing the desired fruit formation through the application of different plant growth hormones, for example, auxins.

2. What do you mean by emasculation?

Emasculation is the process of removing the stamens or the anthers of bisexual flowers. However, during the process, the female reproductive organs are not at all affected. This said technique is known by the name of artificial hybridization. However, when doing such experiments, it is imperative to understand that one should use only desired pollen grains and the stigma of the flower should be protected effectively from the contamination from any kind of unwanted pollen. 

3. How does self-incompatibility restrict autogamy? How does pollination occur in such plants?

Self-incompatibility prevents autogamy through a process called self-sterility. It is a genetic technique with the help of which the process of germination of the pollen grains or the growth of the pollen tube is inhibited. This way the pollen cannot fertilize the ovules. These kinds of plants pollinate through a process called cross-pollination. To get an elaborate explanation about crop pollination, visit Vedantu website or Vedantu Mobile app. The solutions provided by Vedantu are free of cost.

4. Please explain polyembryony.

If more than a single embryo is present in one seed, the phenomenon is known as polyembryony. It is usually seen in some varieties of citrus fruits as well as mango. It plays a crucial role in the breeding of plants and horticulture. These embryos can give birth to healthy plantlets free of viruses. Hybrid species of these plants and fruits are grown extensively nowadays. The varieties obtained through this method are extremely productive.

5. What is the difference between apomixis and parthenocarpy?

In parthenocarpy, fruit can be produced even if the female gamete is not fertilized. This process is utilised for producing seedless fruits like bananas and grapes in the commercial field.

 

In apomixis also, the seeds can be produced with no fertilization but the whole process takes place in the reproductive tract of the female plant. Here, a megaspore mother cell need not undergo meiosis. This process helps in producing hybrid and virus-free varieties.

6. Elaborate on the disadvantages of self¬pollination?

There are a few significant disadvantages of the process of self-pollination:

  • Reducing vigour in the plants that are produced with self-pollination.

  • Decrease in the yield.

  • The number and size of the seeds continue to decrease with l generations.

  • Plants are vulnerable to diseases.

7. Define ornithophily, chiropterophily and malacophilous?

The definition are as follows:

  • Ornithophily is when pollination is carried out with the help of small birds.

Eg: Australian plants.

  • Chiropterophily refers to pollination with the help of bats.

Eg: Sausage tree.

  • Malacophily is the process of pollination with the help of Snails