NCERT Class 12 Biology: Chapter –2 Sexual Reproduction in Flowering Plants Part 3

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Question 17:

In the embryos of a typical dicot and a grass, true homologous structures are:

a. Coleorhiza and coleoptile

b. Coleoptile and scutellum

c. Cotyledons and scutellum

d. Hypocotyl and radicle.

Answer: (c)

Question 18:

The phenomenon observed in some plants wherein parts of the sexual apparatus is used for forming embryos without fertilisation is called:

a. Parthenocarpy

b. Apomixes

c. Vegetative propagation

d. Sexual reproduction.

Answer: (b)

Question 19:

In a flower, if the megaspore mother cell forms megaspores without undergoing meiosis and if one of the megaspores develops into an embryo sac, its nuclei would be:

a. Haploid

b. Diploid

c. A few haploid and a few diploid

d. With varying ploidy.

Answer: (b)

Question 20:

The phenomenon wherein, the ovary develops into a fruit without fertilisation is called:

a. Parthenocarpy

b. Apomixis

c. Asexual reproduction

d. Sexual reproduction

Answer: (a)

Very Short Answer Type Questions

Question 1:

Name the component cells of the ‘egg apparatus’ in an embryo sac.

Answer:

Synergids, egg cells and the fill form apparatus

Explanation: The cells in the embryo sac are distributed such that the three cells are grouped together at the Micropyle end and constitute the egg apparatus. Hence the component cells of the ‘egg apparatus’ in an embryo sac are two synergids (supporting cells), one egg cell and the fill form apparatus.

Question 2:

Name the part of gynoecium that determines the compatible nature of pollen grain.

Answer:

Pistil has the ability to recognize a compatible pollen grain.

Question 3:

Name the common function that cotyledons and nucellus perform.

Answer:

Cotyledons and nucellus contain abundant food which is utilized by the developing cells.

Question 4:

Complete the following flow chart

Pollen mother cell → Pollen tetrad → Pollen grain

Answer:

Pollen mother cell → Pollen tetrad → Pollen grain

Question 5:

Indicate the stages where meiosis and mitosis occur (1, 2 or 3) in the flow chart.

Answer:

Megaspores – Meiosis, Embryo sac – Mitosis, Egg - Mitosis

Explanation: Megaspores are produced from megaspore mother cell through the process of Megasporogenesis by meiosis division.

One of the functional megaspore gets developed into embryo sac by the process called Monosporic development by mitotic division.

Embryo sac at maturity is 8-nucleate and 7-celled. And also the cells in the embryo sac are distributed such that the three cells are grouped together at the Micropyle end and constitute the egg apparatus. And the three cells are at the chalazal end and are called the antipodals. So the egg apparatus is situated Micropyle end. So conversion of embryo sac to egg is a mitotic division.

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