NCERT Solutions for Class 12 Chapter 2 Human Reproduction, Download PDF

NCERT Solutions for Class 12 Human Reproduction: Chapter-wise NCERT solutions for Class 12 Biology, Chapter 2, Human Reproduction are available here. There are a total of 23 questions in the exercises given at the end of this chapter. Here, you will find detailed Class 12 Biology NCERT Solutions for all the questions of Chapter 2 Human Reproduction. These solutions are also helpful for students preparing for medical entrance examinations like NEET (National Eligibility cum Entrance Test). 

Highlights of NCERT Solutions for Class 12 Biology Chapter 2 – Human Reproduction

• Introduction to Human Reproduction
• Male Reproductive System
• Female Reproductive System
• Fertilization and Implantation
• Pregnancy and Embryonic Development
• Parturition and Lactation
• Reproductive Health
• Infertility and Assisted Reproductive Technologies
• Key Diagrams and Illustrations

Key Features of NCERT Solutions for Class 12 Biology Chapter 2 – Human Reproduction

• Comprehensive Coverage
• Step-by-Step Approach
• Diagrams and Illustrations
• Clear and Concise Language
• Relevance to Examinations
• Extra Insights
• Practice Exercises
• Applications in Real Life
• Interdisciplinary Connection
• Self-Assessment

Human Reproduction Plants NCERT Solutions

Question 1. Fill in the blanks:

a) Humans reproduce _________. (asexually/sexually)

b) Human’s are__________. Oviparous/viviparous/ovoviviparous)

c) Fertilization is __________ in humans. (external/internal)

d) Male and female gametes are __________. (Diploid/haploid)

e) Zygote is __________. (Diploid/haploid)

f) The process of release of the ovum from a mature follicle is called__________.

g) Ovulation is induced by a hormone called__________

h) The fusion of the male and the female gametes is called ______.

i) Fertilization takes place in the __________.

j) The zygote divides to form __________, which is implanted in uterus.

k) The structure which provides vascular connection between the foetus and uterusis called __________.

Solution 1.

(a) Sexually

(b) Viviparous

(c) Internal

(d) Haploid

(e) Diploid

(f) ovulation

(g) estrogens

(h) fertilisation

(i) ampullary-isthmic junction

(j) blastomers

(k) placenta

NCERT Exemplar Questions: CBSE Class 12 Biology – Chapter 2, Human Reproductions

Question 2. Draw a labelled diagram of male reproductive system.

Solution 2.

Question3. Draw a labelled diagram of female reproductive system.

Solution3.

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

Solution 4.

Two major functions of testis are:

(a) It produces sperms.

(b) It provides nutrition to male germ cells and secretes androgens.

Two major functions of ovary are:

(a) It produces female hormones, progesterone and estrogen. 

(b) Another role of ovaries is to produce and mature ovum (egg cell).

Question 5. Describe the structure of a seminiferous tubule.

Solution 5.

Seminiferous tubules are lined by two types of cells, spermatogonia and sertoli cells from inside. Spermatogonia cells form sperms through mitotic division, while nutrition to germ cells is provided by sertoli cells. The regions outside the seminiferous tubules called interstitial spaces which contain small blood vessels and Leydig cells, androgens are secreted from Leydig cells.

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

Solutaon 6.

As the puberty starts, sperms are produced by immature male germ cells through spermatogenesis in testis. Spermatogenesis is a process in which undifferentiated diplod germ cells produces and differentiate the haploid cells in animals producing sexually.

Through mitotic division, spermatogonia increase its number. Each spermatogonia is diploid and have 46 chromosomes. Then the spermatogonia which are called primary spermatocytes. One primary spermatocyte divides meiotically and produces haploid cells, which are called secondary spermatocytes. Secondary spermatocyes undergo second meiotic division to produce four haploid spermocytes. Through the process of spermiogenesis, the formed spermatids are transformed into spermatozoa. After spermiogenesis sperm heads become embedded in the sertoli cells, and are finally released from the seminiferous tubules by the process called spermiation.

To understand the process in diagrammatical form check Important CBSE Class 12 Biology Diagrams. 

Question 7. Name the hormones involved in regulation of spermatogenesis.

Solution 7.

Spermatogenesis, the process of sperm cell production in the testes, is regulated by several hormones, including:

1. Follicle-Stimulating Hormone (FSH):

   • FSH is produced and released by the anterior pituitary gland.
   • FSH plays a crucial role in stimulating the Sertoli cells within the seminiferous tubules of the testes.
   • FSH also initiates spermatogenesis by stimulating the proliferation of spermatogonia, the initial germ cells in the process.

2. Luteinizing Hormone (LH):

   • LH, also produced by the anterior pituitary gland, has a specific role in regulating the production of testosterone in the Leydig cells of the testes.

3. Testosterone:

   • Although not a hormone produced directly for the regulation of spermatogenesis, testosterone is a critical hormone for the process.
   • It is primarily produced by the Leydig cells in the testes under the influence of LH.
   • It also supports the maturation and differentiation of spermatids into fully functional spermatozoa.
   • Testosterone levels are tightly regulated to ensure optimal spermatogenesis.

Question 8. Define spermiogenesis and spermiation.

Solution 8.

Spermiogenesis

• Spermiogenesis is the process of spermatid maturation and transformation into fully functional spermatozoa or sperm cells.
• During spermiogenesis, the round, haploid spermatids, which are produced through spermatogenesis, undergo a series of structural and functional changes to acquire their distinctive shape and features.

Spermiation

• Spermiation is the final step in the maturation of sperm cells within the seminiferous tubules of the testes.
• It involves the release or detachment of fully mature spermatozoa from the supporting Sertoli cells in the testes, allowing them to enter the lumen of the seminiferous tubules.

Question 9. Draw a labelled diagram of sperm.

Solution 9.

Question 10. What are the major components of seminal plasma?

Solution 10.

Fructose, calcium and certain enzymes are the main components of seminal plasma.

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

Solution 11.

They store and transport the semen into urethra from testis.

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

Solution 12.

The process of formation of mature female gamete in ovaries is called oogenesis. Initial step is the production of egg which starts prior to birth. Oogonia is formed through mitosis. Oogonia is a diploid cell which develops into primary oocyte through first step of meiotic division. These oocyte develops (one at a time) and when primary oocyte develops, it undergoes meiosis-1 and forms a large secondary oocyte with a small polar body.

Meiosis-2 does not take place in first polar body, where as secondary oocyte enters metaphage stage of meiosis 2. But for completing second meiosis, it awaits for arrival spermatozoa. As sperm enters, it restarts the process of cell cycle by breaking down MPF and turning on APCC. After this, meiosis-2 completes and secondary oocyte converted into fertilized egg or zygote.

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

Solution 13.

Question 14. Draw a labelled diagram of a Graafian Follicle?

Solution 14.

Question 15. Name the functions of the following.

(a) Corpus luteum

(b) Endometrium

(c) Acrosome

(d) Sperm tail

(e) Fimbriae

Solution 15.

(a) Corpus luteum :- It secretes progesterone. Progesterone is essential for maintenance of endometrium.

(b) Endometrium:- Implantation of fertilized ovum and many events of pregnancy takes place in endometrium.

(c) Acrosome: - It is filled with enzymes that help in fertilisation of ovum.

(d) Sperm tail: - It provides mortility to sperms.

(e) Fimbriae: - After ovulation, it helps in collection of ovum.

Question 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 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 16.

(a) False. Leydig cells produce androgens.

(b) True.

(c) False. Leydig cells are found in seminiferous tubules.

(d) True.

(e) False. Oogenesis takes place in ovary.

(f) True.

(g) True.

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

Solution 17.

In human beings, at an average internal of 28-29 days menstruation is repeated and menstrual cycle of events that takes place from one menstruation till the next one.

Estrogen plays an important role in menstrual cycle. When FSH level increases, it stimulates the growth of ovarian follicles and formation of estrogens.

Question 18. What is parturition? Which hormones are involved in induction of parturition?

Solution 18.

The process of delivery of the fetus is called parturition. Oxytocin hormone causes strong contraction of uterine. Contraction of uterine becomes stronger and stronger by the stimulatory reflex between uterine contraction and oxytocin secretion. This leads to expulsion of baby out of uterus through the birth canal.

Question 19. In our society the women are often blamed for giving birth to daughters. Can you explain why this is not correct?

Solution 19.

The sex chromosome in human female is XX while of male is XY. Thus, female produces haploid gametes having all X chromosomes but male produces two types of sex chromosomes X and Y. So, it depends upon the male gametes whose sex chromosomes either X or Y fertilises with female sex chromosome X.

Question 20. How many eggs are released by a human ovary in a month? How many eggs do you think would have been released if the mother gave birth to identical twins? Would your answer change if the twins born were fraternal?

Solution 20.

One ovum is released by a human ovary in a month.

Identical twins are developed from single egg.

If the twins are fraternal twins then they must have been developed from two eggs.

Question 21. How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies?

Solution 21.

Dogs are polyovulatory and they releases more than one ovary at a time. So, a female dog releases six haploid eggs that are fertilised by six sperms to give birth to six puppies.