NCERT Questions for Class 12 Biology Chapter 2 – Human Reproduction

Important Questions with Solutions of Class 12 Biology Chapter 2 – Human Reproduction

1) (a). Why is the starting half of the menstrual cycle stated as the follicular/proliferative stage?

Ans – The occurring transformation of the primary follicles into Graafian follicles under FSH stimulation, in the beginning half of the menstrual cycle leads to the secretion of estrogens by the Graafian follicles and is responsible for the enlargement stimulation of the Endometrium in the uterus. This is why the beginning half of the menstrual cycle is known as the follicular phase or the proliferative phase.

(b). Why is the second or the next half of the menstrual cycle known as the luteal or the secretory phase?

Ans – This is because of the secretion of a large quantity of progesterone by the corpus luteum in the second or the next half of the menstrual cycle.

2) Explain L. H. Surge along with its roles.

Ans – The menstrual cycle is divided into three parts and they are:

Follicular phase, Ovulatory phase and Luteal phase.

In the case of L. H., i.e. luteinizing hormone, the ovulatory phase pertains the most significant role along with the follicle being developed in the follicular phase as the uterine lining sheds and cleanses itself in the preparation for ovulation in the ovulatory phase, the cycle begins.

3) State any two functions of a female placenta.

Ans –

• The female placenta, is the structural and functional unit between the developing embryo, the nutritional supply from the mother & oxygen to the embryo.
• It also helps to remove carbon dioxide and other excretory products by the embryo, along with being an endocrine tissue, producing various hormones.

4) How is the statement below valid:
‘How can a fertilized egg become the blueprint of advanced development?’

Ans – In the form of 23 chromosomes, the sperm carries the genetic information of the father and mother, i.e., male (X or Y) and female (X) sex chromosomes. Thus, by introducing variation in the offspring during fertilization, the male and the female gamete produce a new genetic combination through fusion. The development of the embryo is controlled by the zygote or the fertilized egg, containing the genetic information.

5) Distinguish between spermatogenesis and oogenesis.

Ans – The differences between spermatogenesis and oogenesis are:

Spermatogenesis	Oogenesis
The location of its occurrence is inside the testes.	The location of its occurrence is inside the ovary.
Completion of all the phases occurs inside the testes.	Completing the major phases occurs inside the ovary, whereas the last stage is in the oviduct.
Spermatogenia develops from the germinal epithelial lining of the seminiferous tubules.	The germinal epithelium by the ovary gives rise to the oogonia.
Spermatocytes is risen by all spermatogonia.	Oocytes are raised by selective oogenia.
Two secondary spermatocytes are developed by dividing the primary spermatocytes by meiosis.	In the meiosis process, one secondary oocyte and a polar body are developed by the primary oocyte.
Two spermatids are developed by dividing the secondary spermatocytes by meiosis 2.	The ovum and the second polar body are developed by dividing the secondary oocytes by meiosis 2.
Each spermatid is separated into spermatozoan or sperm.	In this process, meiosis 2 results in no further differentiation.
The sperms evolved due to this process and are capable of motion.	The ovum or egg evolved due to this process and is incapable of motion.

6) Testes of human males are known for being extra-abdominal. Explain.

Ans – The scrotum is a pouch outside the abdominal cavity containing the testis and thus is known for being extra abdominals. The scrotum pertains to a temperature of 2-3 oC less than the body temperature necessary for spermatogenesis.

7) Define colostrum. State its significance to a newbie.

Ans – The milk obtained from mammary glands after 2 or 3 days of birth, is called colostrum. It being rich in proteins and low in fats, also contains the antibody lgA providing immunity to newborn infants.

8) Explain the location of the process of oogenesis along with its stages.

Ans – Oogenesis is the emergence and development of the ovum. The process continued in the ovary starting during the embryonic development of the female fetus. The 3 methods of this process are:

1. Multiplication phase: During meiosis when the primordial germ cells split, oogonia is produced. These oogonia form clusters while being in the process of laying repeated mitotic divisions. Out of all the clusters, one being the number entering into the growth phase is known as the primary oocyte.
2. Growth phase: Followed by puberty and hits the growth phase, increasing the size of oocytes to many folds, and paves the way for the synthesis.
3. Maturation phase: Two haploid(n) cells are produced due to the first division in the meiotic. This division is followed by unequal cytokinesis, a secondary oocyte being a large daughter cell with almost all cytoplasm, and a polar body being a smaller me with less cytoplasm. An ovum and a secondary polar body are formed due to the secondary oocyte undergoing a second meiotic division.