NCERT Solutions Class 12 Biology Chapter 2 Human Reproduction

Chapter 2, Human Reproduction, from Class 12 biology teaches about how the human body produces gametes, supports fertilisation and development of a baby. This chapter clearly explains the structure and functions of the male and female reproductive systems, the process involved in the formation of gametes, menstrual cycle, fertilisation, and stages of embryonic development.

ALLEN brings you a set of comprehensive solutions designed to make biology both interesting and easy to grasp. Our team focuses on using clear language and high-quality diagrams to help you visualize every stage of development. Instead of just memorizing facts, these solutions help you understand the "how" and "why" of human biology. By choosing ALLEN’s resources, you’re gaining a clear, expert-verified perspective that simplifies your study routine and boosts your confidence for the CBSE finals and NEET Exams.

1.0Download NCERT Solutions Class 12 Biology Chapter 2 Human Reproduction : Free PDF

This chapter focuses on explaining how a human reproductive system functions and how a new life begins after fertilisation. The NCERT Solutions for Class 12 Biology Chapter 2 Human Reproduction help students revise key stages and practise textbook questions easily. Download the free PDF now to study anytime and prepare confidently for exams.

2.0Class 12 Biology Chapter 2: Key Concepts

In this chapter, the structure and processes involved in human reproduction is explained clearly. Some of the key lessons covered in this chapter are given below:

• Male Reproductive System: Understand the structure and functions of testes, ducts, and accessory glands.
• Female Reproductive System: Studying ovaries, oviducts, uterus, and their roles in reproduction.
• Gametogenesis: Learning about spermatogenesis and oogenesis.
• Menstrual Cycle: Understanding different phases and hormonal control of the cycle.
• Fertilisation and Implantation: Studying how the sperm and ovum fuse and how the embryo attaches to the uterus.
• Embryonic Development: Learning the early stages of development from zygote to foetus.
• Lactation: Understanding the role of hormones in milk production after birth.

3.0NCERT Class 12 Biology Chapter 2 Human Reproduction : Detailed Solutions

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 _____________ 

Ans:

(a) Sexually

(b) Viviparous 

(c) Internal

(d) Haploid

(e) Diploid 

(f) Ovulation

(g) Luteinising Hormone (LH)

(h) Fertilisation

(i) Fallopian tube (oviduct)

(j) Blastocyst

(k) Placenta

2. Draw a labelled diagram of male reproductive system. 

3. Draw a labelled diagram of female reproductive system. 

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

Ans: The two major functions of testus and ovary are:

Testis:

• Spermatogenesis: It is the process by which the male gametes (spermatozoa) are produced.
• Hormone Secretion: Testis is where the synthesis and secretion of testosterone  (androgens) takes place.

Ovary:

• Oogenesis: This is the process of production of the female gamete (ovum).
• Hormone Secretion: Ovaries secrete hormones, including estrogen and progesterone.

5. Describe the structure of a seminiferous tubule. 

Ans: Seminiferous tubules are highly coiled tubular structures present in the testicular lobules of the testes that are responsible for the production of male gametes (sperms). Below is the basic structure:

• Location: Seminiferous tubules are the highly coiled structures found inside the testicular lobules.
• Lining: Two types of cells, namely, male germ cells (spermatogonia) and Sertoli cells, are present inside the lining of the seminiferous tubule.
• Germ Cells: These cells undergo meiotic divisions to eventually form spermatozoa.
• Sertoli Cells: Sertoli cells provide nutrition and support to the developing germ cells.
• Interstitial Space: The region outside the tubules, which contains blood vessels and Leydig cells (interstitial cells), is called the interstitial space, and they secrete testicular hormones (androgens).

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

Ans: The process of formation of haploid spermatozoa from diploid spermatogonia in the testes is called Spermatogenesis. The process of spermatogenesis is given below: 

• Multiplication Phase: Spermatogonia (2n) undergo mitotic division and multiply.
• Growth Phase: During this phase, some spermatogonia differentiate into primary spermatocytes (2n).
• Maturation Phase: Primary spermatocytes undergo the first meiotic division to form two equal haploid secondary spermatocytes (n).
• These undergo the second meiotic division to produce four haploid spermatids.
• Spermatids differentiate into spermatozoa (sperm) by a process called spermiogenesis.

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

Ans:

• Gonadotropin-releasing hormone (GnRH): These are secreted by the hypothalamus.
• Luteinizing Hormone (LH): They act on Leydig cells to stimulate secretion of testosterone (androgen).
• Follicle Stimulating Hormone (FSH): This acts on Sertoli cells to stimulate factors for spermiogenesis.
• Androgens (Testosterone): Essential for stimulating the process of sperm production in the seminiferous tubules..

8. Define spermiogenesis and spermiation. 

Ans:

• Spermiogenesis: The process of transformation of non-motile spermatids into mature, motile spermatozoa.
• Spermiation: The process where the mature spermatozoa are released from the Sertoli cells into the lumen of the seminiferous tubules is called spermiation.

9. Draw a labelled diagram of sperm. 

10. What are the major components of seminal plasma? 

Ans: Seminal plasma is the fluid part of semen, contributed by the prostate gland, seminal vesicles, and bulbourethral glands. It is rich in:

• Fructose (energy source)
• Calcium
• Certain Enzymes

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

Ans: The major functions of the male accessory ducts and glands are given below:

Male Accessory Ducts (rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct, urethra):

• Provide a passage and temporary storage for sperms
• Help in the transport of sperms from testes to the exterior
• Allow maturation of sperms (mainly in the epididymis)

Male Accessory Glands (seminal vesicles, prostate gland, bulbourethral glands):

• Secrete seminal fluid that forms the seminal plasma
• Provide nutrition (fructose) to sperms
• Maintain a slightly alkaline medium for sperm survival and motility
• Help in lubrication of the urethra

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

Ans: Oogenesis is the process of formation of a mature female gamete in the ovaries.

• Foetal stage: It is initiated during embryonic development. No additional oogonia are formed after birth.
• Foetal Stage: Oogonia multiply by mitosis and differentiate into primary oocytes.
• Meiotic Arrest: Primary oocytes enter meiosis I and get arrested at prophase I until puberty.
• At Puberty: In each menstrual cycle, one primary oocyte completes meiosis I to form a secondary oocyte and a first polar body.
• Second Meiotic Arrest: The secondary oocyte begins meiosis II and is arrested at metaphase II.
• Completion: Meiosis II is completed only after fertilisation, forming a mature ovum and a second polar body.
• Only one functional ovum is formed, while polar bodies degenerate.

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

14. Draw a labelled diagram of a Graafian follicle? 

15. Name the functions of the following: 

(a) Corpus luteum 

(b) Endometrium 

(c) Acrosome 

(d) Sperm tail 

(e) Fimbriae 

Ans:

(a) Corpus luteum: Large amounts of progesterone are secreted, which are essential for maintaining the endometrium.

(b) Endometrium: The fertilised ovum is implanted here. It also undergoes cyclic changes during the menstrual cycle.

(c) Acrosome: It is a cap-like organelle at the tip of the sperm nucleus. It contains enzymes that help the sperm penetrate the ovum's membrane.

(d) Sperm tail: It provides motility to the sperm, enabling it to swim toward the ovum.

(e) Fimbriae: They are the finger-like projections at the distal end of the fallopian tube that help in the collection of the ovum after ovulation.

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) 

Ans:

(a) False. Androgens are produced by Leydig cells.

(b) True.  

(c) False. Leydig cells are found in the testes.

(d) True.

(e) False. Oogenesis takes place in the ovary (specifically follicles).

(f) True.

(g) True.

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

Ans: The menstrual cycle is a monthly reproductive cycle in females involving ovarian and uterine changes for preparation of pregnancy. Different pahses involved in the menstrual cycle are Menstrual phase, Follicular phase, Ovulatory phase, and Luteal phase.

Hormones regulating the Menstrual cycle

• Gonadotropin-releasing hormone (GnRH) – They are released from the hypothalamus and controls the release of pituitary hormones
• Follicle-stimulating hormone (FSH) – They are essential for stimulating the growth of ovarian follicles
• Luteinizing hormone (LH) – This hormone triggers ovulation and the formation of corpus luteum
• Estrogen – Helps in the development of the uterine lining (endometrium)
• Progesterone – It maintains the uterine lining for possible pregnancy

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

Ans: The processof child birth, where the fully developed foetus is expelled from the uterus through the birth canal at the end of pregnanacy is called parturition.

• Mechanism: Induced by a complex neuroendocrine mechanism starting with the "fetal ejection reflex."
• Hormones: Oxytocin is released from the maternal pituitary, causing stronger contractions, which in turn stimulate stronger contractions.

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

Ans: Women cannot be blamed for giving birth to daughters because, sex in humans is determined by the sex chromosomes of the sperm, not the egg.

• Females produce only one type of gamete (X).
• Males produce two types of gametes (X and Y).
• If a sperm carrying an X fertilizes the egg, the child is a girl (XX). If a sperm carrying a Y fertilizes the egg, the child is a boy (XY). 

Thus, the father determines the baby's sex.

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? 

Ans: Monthly Release: 1 egg.

Identical Twins: 1 egg was released (it split into two embryos after fertilization).

Fraternal Twins: 2 eggs were released (each fertilized by a different sperm).

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

Ans: In dogs, multiple ovulations occur, and each puppy develops from a separate fertilized egg. Therefore, in order to give birth to 6 puppies, 6 eggs must have been released by the ovary of the female dog.

4.0Key Features of NCERT Solutions for Class 12 Biology Chapter 2

• Reproductive structures and their functions are clearly explained to help students understand anatomy and functions clearly.
• The resource offers solutions to the NCERT textbook content and matches the CBSE board exam pattern.
• Regular revision of this solution can help improve recall of important terms and process.
• Gaining strong fundamentals support the preparation for NEET and advanced studies in human biology.
• Clear explanations provided help students connect textbook knowledge with real-life health and development concepts.