1. Home
  2. |  
  3. CBSE Board |  

NCERT Solutions for CBSE Class 12 Biology ‒ Chapter 2: Sexual Reproduction in Flowering Plants

May 4, 2017 13:10 IST

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

    Image source: NCERT textbook for Class 12 Biology

    Chapter wise NCERT solutions for class 12 Biology, Chapter 2, Sexual Reproduction in Flowering Plants are available here. There are total 18 questions in the exercises given at the end of this chapter. Here, you will find detailed solutions to all the questions. These solutions are also helpful for students preparing for medical entrance examinations like NEET (National Eligibility cum Entrance Test). 

    Question1. Name the parts of an angiosperm flower in which development of male and female gametophyte take place.

    Solution1.

    Pollen grains represent the male gametophyte in an angiosperm which develops inside the microsporangia. On the other hand, female gametophytes of angiosperms are formed from the megaspore through the process of reduction division which lies inside the nucellus of ovule.

    Question2. 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.

    Solution2.

    Microsporogenesis

    Megasporogenesis

    1. Formation of microspore from mother cells.

    1. Formation of megaspore from megaspore mother cell.

    2. This process forms thousands of microspores and pollen grains.

    2. Only one functional megaspore is formed.

    3. It occurs inside the anther.

    3. It occurs inside the nucellus of developing ovule.

    In both the processes, meiosis takes place.

    Pollen grains formed at the end of microsporogenesis and female gametophytes formed at the end of megasporogenesis.

    Question3. Arrange the following terms in a correct developmental sequence:

    Pollen small piece, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.

    Solution3.

    Sporogenous tissue, microspore tetrad, pollen mother cell, pollen grain, male gametophyte.

    CBSE Class 12 Biology Syllabus 2017 - 2018

    Question4. With a neat labelled diagram, describe the parts of a typical angiosperm ovule.

    Solution4.

     NCERT Solutions for Class 12 Biology, Chapter 2, Answer 4: labelled diagram of a typical angiosperm ovule

    Question5. What is meant by monosporic development of female gametophyte?

    Solution5.

    In the process of megasporogenesis, one megaspore mother cell divides by mitotic division to produce four megaspores. In many angiosperms one megaspore develops into female gametophyte and rest of the three get degenerate. This is termed monosporic development of female gametophyte.

    Question6. With a neat diagram explain the 7-celled, 8-nucleate mature female gametophyte.

    Solution6.

    Neat diagram of 7-celled, 8-nucleate mature female gametophyte

    Question7. What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.

    Solution7.

    Those flowers which have exposed anthers and stigma are called chasmogamous flowers.

    No, cross-pollination can occur in cleistogamous flowers because cleistogamous flowers are bisexual flowers and do not open at all for complete self-pollination.

    Question8. Mention two strategies evolved to prevent self-pollination flowers.

    Solution8.

    Two strategies evolved to prevent self-pollination are:-

    (a) Dichogamy – In this, pollen and stigma of flowers get mature at different periods or times. Dichogamy is of two types, Protogyny- If gynoecium matures earlier than androcium. e.g.; bajra. Protandry- If androecium matures earlier than gynoecium. e.g.; maize.

    (b) Self-incompatibility – It is the genetic inability of certain pollen grains to fertilize the ovules of same flower or plant.

    NCERT Exemplar Questions:  Class 12 Biology – Chapter 2, Sexual Reproduction in Flowering Plants

    Question9. What is self incompatibility? Why does self pollination not lead to seed formation in self incompatible species?

    Solution9.

    Self incompatibility is also called self sterility. It is the natural inability to prevent self pollination in which pollen grains from the same flower is unable to fertilize ovules of same flower or plant.

    It happens due to several complex mechanisms. These could be saprophytic or gametophytic incompatibility. Prevent of pollen germination, retardation of growth, reorientation of pollen tube, failure of nuclear fusion could be one of the reason.

    Question10. What is bagging technique? How is it useful in a plant breeding programme?

    Solution10.

    Bagging is a technique used to prevent the fertilization of stigma from unwanted pollen by covering the emasculated flower with butter-paper. It is useful in a plant breeding programme because it prevents from unwanted cross pollination.

    Question11.What is triple fusion?

    Solution11.

    It is fusion of three haploid nuclei during double fertilization. It takes place in the central cell between one male gamete and two polar nuclei and it forms triploid primary endosperm nucleus.

    Question12. Why do you think the zygote is dormant for sometime in a fertilized ovule?

    Solution12.

    It is so because development of endosperm precedes development of embryo and nutrition to developing embryo is provided by endosperm tissue.

    Class 12 NCERT Biology Textbook, Chapter-2: Sexual Reproduction In Flowering Plants

    Question13. Differentiate between:

    (a) Hypocotyl and epicotyl

    (b) Coleoptile and coleorrhiza

    (c) Integument and Testa

    (d) Perisperm and pericarp

    Solution13.

    (a) Hypocotyl and epicotyl

    Hypocotyl

    Epicotyl

    It is a cylindrical portion below the level of cotyledons.

    The portion of embryonal axis above the level of cotyledons.

    It terminates as its lower end in radical or root tip.

    It terminates with the plumule or stem tip.

    (b) Coleoptile and coleorrhiza

    Coleoptile

    Coleorrhiza

    Epicotyl has a shoot apex and a few leaf primordial enclosed in hollow foliar structure called Coleoptile.

    At the lower end of embyonal axis, it has the radical and root cap enclosed in undifferentiated sheath called coleorrhiza.

     

     

    (c) Integument and Testa

    Integument

    Testa

    They are the protective covering of ovules.

    It is the outer seed coat.

    Except micropylar end it encircles the complex ovule.

    It protects the young embryo because of its hardness.       

    (d) Perisperm and pericarp

    Perisperm

    Pericarp

    Residual persistent nucellus is called perisperm.

    It is fruit’s wall which developed from wall of ovary.

    It is single layered.

    It may have three layers i.e., exocarp, mesocarp and endocarp.

    Question14. Why apple is called a false fruit? Which parts of the flower forms the fruit?

    Solution14.

    Apple is called a false fruit because the thalamus also contributes in the formation of fruit.

    Fruits are mainly matured ovary together with structures close to ovary but after the formation of fruit, structures other than ovary degenerates and fall off.

    Question15. What is meant by emasculation? When and why does a plant breeder employ this technique?

    Solution15.

    It is a technique done manually in which anthers from flower bud are removed before the pollen dehisces. It is done by plant breeders to produce species of plants having desirable characters by cross-pollination of own choice.

    Question16. If one can induce parthenocarpy through the application of growth substances, which fruits you would select to induce parthenocarpy and why?

    Solution16.

    It is a process in which fruits are produced by the use of growth hormones like auxins and gibberellines. It is either done natural or induced. No fertilization takes place in parthenocarpic fruits.

    Fruits like oranges, lemons can be easily produced by the process of parthenocarpy.

    Question17. Explain the role of tapetum in the formation of pollen grain wall.

    Solution17.

    Innermost wall of microsporangium is called tapetum. Tapetal cells may have uni, bi or multi nucleate and have dense cytoplasm.

    Role played by tapetum are as following:-

    a) It secretes hormones and various enzymes.

    b) During meiosis in spore mother cells, tapetum supports nutrition to anther locule.

    c) It produces ubisch bodies which are coated with sporopollenin to cause thickening of exine.

    d) It secretes protein for pollen to be compatible during recognition.

    Question18. What is apomixes and what is its important?

    Solution18.

    In apomixes process, seeds are produced without fertilization. It is a form of asexual reproduction which is somewhat similar to sexual reproduction.

    For hybrid seed industry, apomixes is very important because year after year seeds needs to be produced, which makes these seeds very costly. There won’t be any segregation of characters in hybrids, if the hybrids are made apomicts. Thus, making these seeds to be used year after and that makes hybrid seeds very economical.

    Download NCERT Solutions for Class 12 Biology ‒ Chapter 2: Sexual Reproduction in Flowering Plants in PDF format

    NCERT Solutions for Class 12 Biology ‒ Chapter 1 Reproduction in Organisms

    NCERT Solutions for Class 12 Biology ‒ Chapter 3 Human Reproductions

    NCERT Solutions for Class 12 Biology ‒ Chapter 4: Reproductive Health

    Latest Videos

    Register to get FREE updates

      All Fields Mandatory
    • (Ex:9123456789)
    • Please Select Your Interest
    • Please specify

    • ajax-loader
    • A verifcation code has been sent to
      your mobile number

      Please enter the verification code below

    This website uses cookie or similar technologies, to enhance your browsing experience and provide personalised recommendations. By continuing to use our website, you agree to our Privacy Policy and Cookie Policy. OK
    X

    Register to view Complete PDF