NCERT Class 12 Biology: Chapter –3 Human Reproduction Part 4

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Question 7:

What is the significance of epididymis in male fertility?

Answer:

Epididymis is a coiled structure within the scrotum that plays a significant role in male fertility:

1. Sperms mature physiologically, their motility and fertilising capacity increases within the epididymis.

2. It also helps in the transportation of sperms.

Question 8:

Give the names and functions of the hormones involved in the process of spermatogenesis. Write the names of the endocrine glands from where they are released.

Answer:

Hormone, Gland and Function
Chapter 3 - Question 8- Hormone, Gland and Function

Hormone

Gland

Function

1. Gonadotrophin Hormone (GnRH)

Hypothalamus Gland

Acts on pituitary gland to release FSH and LH

2. Lutenizing Hormone (LH)

Pituitary Gland

Acts on Leydig cells to release testosterone.

3. Androgens

Testis

It stimulates the process of spermatogenesis

4. Follicle Stimulating Hormone (FSH)

Pituitary Gland

It stimulates testicular growth and the production of androgen binding protein that helps the mature sperm to sustain.

Question 9:

The mother germ cells are transformed into a mature follicle through series of steps. Provide the missing steps in the blank boxes.

The mother germ cells

The Mother Germ Cells

The mother germ cells

Answer:

The mother germ cells

The Mother Germ Cells

The mother germ cells

Question 10:

During reproduction, the chromosome number (2n) reduces to half (n) in the gametes and again the original number (2n) is restored in the offspring, What are the processes through which these events take place?

Answer:

During gametogenesis, the chromosome number (2n) reduces to half (n) and the actual number (2n) of chromosomes are restored in the offspring after Fertilisation.

Question 11:

What is the difference between a primary oöcyte and a secondary oöcyte?

Answer:

Primary Oöcyte and a Secondary Oöcyte
Primary oöcyte and a secondary oöcyte

Primary Oocyte

Secondary Oocyte

1. Primary oocyte are diploid by nature

1. Secondary oocyte are haploid by nature.

2. Developed from oogonia

2. Developed from primary oocyte through meiosis 1

3. Found in primary follicles

3. Found in the mature graafian follicle.

Question 12:

What is the significance of ampullary–isthmic junction in the female reproductive tract?

Answer:

Ovum fertilization takes place at the ampullary-isthmic junction in the female reproductive tract.

Question 13:

How does zona pellucida of ovum help in preventing Polyspermy?

Answer:

Polyspermy refers to the fertilization of an egg through more than one sperm. Proteases destroy the protein link between the cell and vitelline membrane as well as between the receptor protein and any other sperm bound to it, hence, prevents polyspermy.

Question 14:

Mention the importance of LH surge during menstrual cycle.

Answer:

LH or luteinizing hormone surge leads to the rupture of Graafian follicle and releases ovum into the fallopian tube. LH surge is responsible for luteal phase in the ovarian cycle.

Question 15:

Which type of cell division forms spermatids from the secondary spermatocytes?

Answer:

In the first meiotic (meiosis I) division, the primary spermatocyte divides into two secondary spermatocytes. Each secondary spermatocyte formed, then divides into spermatids through second meiotic division (meiosis II)

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