NCERT Solutions for Class 12 Biology Chapter 3 Human Reproduction is framed by subject experts and comprises detailed answers for reference. All the questions given in the exercises from the textbook are answered here. Students can refer to these answers to prepare for the board examinations. The answers provided in the NCERT Solutions for Class 12 are beneficial to enhance conceptual knowledge.

Chapter 3 Human Reproduction of Class 12 Biology is formulated according to the CBSE Syllabus for 2022-23. Solutions provided are solved skillfully with the use of student-friendly terminologies simultaneously aligning with the standards that are to be followed for solving the NCERT Solutions for Class 12. Practising these solutions can prove to be extremely beneficial not only from the board examination point of view, but can also help Class 12 students to outperform in the upcoming competitive examinations.

Exercise

1. Fill in the blanks:

(a) Humans reproduce _____________ (asexually/sexually)

(b) Humans are _____________ (oviparous, viviparous, ovoviviparous)

(c) Fertilisation is _____________ in humans (external/internal)

(d) Male and female gametes are _____________ (diploid/haploid)

(e) Zygote is _____________ (diploid/haploid)

(f) The process of release of ovum from a mature follicle is called _____________

(g) Ovulation is induced by a hormone called _____________

(h) The fusion of male and female gametes is called _____________

(i) Fertilisation takes place in _____________

(j) Zygote divides to form _____________which is implanted in uterus.

(k) The structure which provides vascular connection between foetus and uterus is called _______

Solution:

(a) Humans reproduce sexually.

(b) Humans are viviparous.

(c) Fertilisation is internal in humans

(d) Male and female gametes are haploid

(e) Zygote is diploid

(f) The process of release of ovum from a mature follicle is called ovulation

(g) Ovulation is induced by a hormone called luteinizing hormone (LH)

(h) The fusion of male and female gametes is called fertilization

(i) Fertilisation takes place in ampulla of oviduct

(j) Zygote divides to form blastocyst which is implanted in uterus.

(k) The structure which provides vascular connection between foetus and uterus is called placenta

2. Draw a labelled diagram of male reproductive system.

Solution:

The diagram of male reproductive system is as follows:

3. Draw a labelled diagram of female reproductive system.

Solution:

The diagram of female reproductive system is as follows:

4. Write two major functions each of testis and ovary.

Solution:

Two major functions of each are as follows:

Testis:

Ovary:

5. Describe the structure of a seminiferous tubule.

Solution:

Structure of seminiferous tubules:

6. What is spermatogenesis? Briefly describe the process of spermatogenesis.

Solution:

The phenomena of sperm production from the immature germ cell in males is termed as spermatogenesis. The process occurs in the seminiferous tubules located inside the testes. In this process, a diploid male germ cell or spermatogonium enlarges (in size) for the formation of a diploid primary spermatocyte which inturn goes through the first meiotic division or meiosis I. This division is a reductional division for the formation of two equal haploid secondary spermatocytes, each of which further undergoes second meiotic division or meiosis II for the formation of two equal haploid spermatids.

Subsequently, four haploid spermatids are formed from a diploid spermatogonium. The spermatids hence produced alter to form spermatozoa(sperm) through the process of spermiogenesis.

7. Name the hormones involved in regulation of spermatogenesis.

Solution:

Some hormones involved in the regulation of spermatogenesis are as listed below:

8. Define spermiogenesis and spermiation.

Solution:

Spermiogenesis It is the phenomena of transformation of non-motile spermatids to mature, motile spermatozoa.

Spermiation It is the phenomena where mature spermatozoa are released from the Serotoli cells into the lumen of the seminiferous tubules of the testes.

9. Draw a labelled diagram of sperm.

Solution:

The diagram of sperm is as below:

10. What are the major components of seminal plasma?

Solution:

The major components of seminal plasma are:

11. What are the major functions of male accessory ducts and glands?

Solution:

The major functions of the male accessory ducts and glands are as follows:

12. What is oogenesis? Give a brief account of oogenesis.

Solution:

Ooogenesis is the phenomena of formation of haploid female gametes known as ova from diploid oogonia in the ovary, Graffian follicles, to be precise. This process is discontinuous which is initiated during the period of foetal development that is terminated only after puberty sets in.

The process of Oogenesis takes place in three phases:

Multiplicative phase

13. Draw a labelled diagram of a section through ovary.

Solution:

The diagram of a section of an ovary is as follows:

14. Draw a labelled diagram of a Graafian follicle.

Solution:

The diagram of a Graafian follicle is as follows:

15. Name the functions of the following:

(a) Corpus luteum (b) Endometrium

(c) Acrosome (d) Sperm tail

(e) Fimbriae

Solution:

The functions are as follows:

(a) Corpus luteum It is formed when the Graafian follicle ruptures. The corpus luteum secretes the hormone progesterone during the luteal phase of the menstrual cycle. When progesterone is secreted in high levels, the secretion of LH and FSH is inhibited which further prevents ovulation. The corpus luteum facilitates the endometrium of the uterus to proliferate and prepare for the process of implantation.

(b) Endometrium as the name suggests, the endometrium is the innermost lining of the uterus comprising glands that undergoes cyclic changes during different stages of the menstrual cycle in order to prepare itself for the embryo-implantation process.

(c) Acrosome The acrosome is located in the anterior section of the head of the sperm, resembling a cap-like structure. It consists of the hyaluronidase enzyme that hydrolyses the outer membrane of the egg which facilitates the sperm to perforate through the egg during fertilization.

(d) Sperm tail the sperm tail makes up for the longest part of the sperm, enabling the movement of the sperm, once it has entered the female reproductive tract.

(e) Fimbriae Towards the ovarian end of the fallopian tube, finger-like projections emerge. These are the Fimbriae which assist in gathering the ovum after the ovulation process. This is facilitated by the beating of the cilia.

16. Identify True/False statements. Correct each false statement to make it true.

(a) Androgens are produced by Sertoli cells. (True/False)

(b) Spermatozoa get nutrition from Sertoli cells. (True/False)

(c) Leydig cells are found in the ovary. (True/False)

(d) Leydig cells synthesise androgens. (True/False)

(e) Oogenesis takes place in corpus luteum. (True/False)

(f) Menstrual cycle ceases during pregnancy. (True/False)

(g) Presence or absence of hymen is not a reliable indicator of virginity or sexual experience. (True/False)

Solution:

17. What is menstrual cycle? Which hormones regulate menstrual cycle?

Solution:

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NCERT Solutions For Class 12 Biology Chapter 3 - Human Reproduction - BYJUS