Biology Class 12 NCERT Solutions: Chapter 2 Sexual Reproduction in Flowering Plants Part 1

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Q.1 Name the parts of an angiosperm flower in which development of male and female gametophyte take place.

Answer:

The male gametophyte or the pollen grain develops inside the pollen chamber of the anther, whereas the female gametophyte (also known as the embryo sac) develops inside the nucellus of the ovule from the functional megaspore.

Q.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.

Answer:

Table of Microsporogenesis and Megasporogenesis
Table of Microsporogenesis and Megasporogenesis

Microsporogenesis

Megasporogenesis

1.

It is the process of the formation of microspore tetrads from a microspore mother cell through meiosis.

It is the process of the formation of the four megaspores from a megaspore mother cell in the region of the nucellus through meiosis.

2.

It occurs inside the pollen sac of the anther.

It occurs inside the ovule.

3.

Microspore leads to development of male gametophyte.

Leads to formation of female gametophyte (embryo sac).

4.

Many spore mother cells is involved.

Only One spore mother cells is involved

  • Both events (microsporogenesis and megasporogenesis) involve the process of meiosis or reduction division which results in the formation of haploid gametes from the microspore and megaspore mother cells.

  • Microsporogenesis results in the formation of haploid microspores from a diploid microspore mother cell. On the other hand, megasporogenesis results in the formation of haploid megaspores from a diploid megaspore mother cell.

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

Answer:

  • The correct development sequence is as follows:

    Image of Development Sequence

    Image of Development Sequence

    Image of Development Sequence

  • During the development of microsporangium, each cell of the Sporogenous tissue acts as a pollen mother cell and gives rise to a microspore tetrad, containing four haploid microspores by the process of meiosis (microsporogenesis).

  • As the anther matures, these microspores dissociate and develop into pollen grains. The pollen grains mature and give rise to male gametes.

Q.4: With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.

Answer:

An ovule is a female megasporangium where the formation of megaspores takes place.

Image of Female Megasporangium

Image of Female Megasporangium

Image of Female Megasporangium

  • The various parts of an ovule are –

  • Funiculus – It is a stalk-like structure which represents the point of attachment of the ovule to the placenta of the ovary.

  • Hilum – It is the point where the body of the ovule is attached to the funiculus.

  • Integuments –They are the outer layers surrounding the ovule that provide protection to the developing embryo.

  • Micropyle – It is a narrow pore formed by the projection of integuments. It marks the point where the pollen tube enters the ovule at the time of fertilization.

  • Nucellus – It is a mass of the parenchymatous tissue surrounded by the integuments from the outside. The nucellus provides nutrition to the developing embryo. The embryo sac is located inside the nucellus.

  • Chalazal – It is the based swollen part of the nucellus from where the integuments originate.