(a) Draw a labelled diagram of the sectional view of microsporangium of an angiosperm.
(b) Explain the development of male gametophyte in the microsporangium.

OR

(a) Name the hormone that initiates spermatogenesis in humans. Describe the process of spermatogenesis in sequence mentioning the ploidy of the cells at each step.

(b) Draw the diagram of a mature human sperm and label the parts that

(i) helps it reaching to the ovum.

(ii) providing energy for it to reach the ovum.

(iii) helping it to gain entry into the ovum.

Question

(a) Draw a labelled diagram of the sectional view of microsporangium of an angiosperm.
(b) Explain the development of male gametophyte in the microsporangium.

OR

(a) Name the hormone that initiates spermatogenesis in humans. Describe the process of spermatogenesis in sequence mentioning the ploidy of the cells at each step.

(b) Draw the diagram of a mature human sperm and label the parts that

(i) helps it reaching to the ovum.

(ii) providing energy for it to reach the ovum.

(iii) helping it to gain entry into the ovum.

Philoid · Accepted Answer

(a)

Figure:Sectional view of microsporangium of an angiosperm

(b) The development of male gametophyte in the microsporangium as follow:

• The each cell of the sporogenous tissue is capable of gives rise to microspore tetrad.

• Each one is potential pollen or microspore mother cell.

• The microsporogenesis is the process of formation of microspores from a pollen mother cell (PMC) through meiosis.

• As microspores are formed, they are arranged in a cluster of four cells that is the microspore Tetrad.

• As the anthers mature and dehydrate after that the microspores dissociate from each other and develop into pollen grains.

• 4-pollen grains represent the male gametophytes and are shed at 2-celled stage.

Explanation:

OR

(a)

• At the age of puberty, spermatogenesis starts due to the secretion of gonadotropin releasing hormone (GnRH). In testis spermatogonia (the immature male germ cells) produce sperms by the process of spermatogenesis.

• On the inside wall of seminiferous tubules, the spermatogonia present and they are multiply by mitotic division and eachspermatogonium is diploid (2N).

• Primary spermatocytes periodically undergo meiosis and complete the first meiotic division (reduction division).

• The first mitotic division leading to the formation of two equal haploid cells (2N) called secondary spermatocytes.

• For the production of 4 equal haploids (N) spermatids, the secondary spermatocytes undergo for the second mitotic division.

• Spermiogenesis is the process by which the spermatids are transformed into spermatozoa (sperms).

• Flow chart of spermatogenesis

(b)

Fig. Mature human sperm

i. Tail

ii. Middle piece/ mitochoridria

iii. Acrosome

Explanation:(a)

(b)