Class 12 Biology Chapter 2 Human Reproduction Solutions. Explore Class 12 Biology Chapter 2 Human Reproduction Solutions with accurate, easy-to-understand answers and exam-ready explanations to boost your preparation and score higher in board exams.

Class 12 Biology Chapter 2 Human Reproduction Solutions

A. Very Short Answer Questions (1 mark each)

1. What are the components of the human male reproductive system?

Ans: The male reproductive system consists of the testes, epididymides, vasa deferentia, ejaculatory ducts, urethra, and penis.

2. What is the primary reproductive organ in males?

Ans: The testes.

3. What is the urethral passage in the penis?

Ans: The urethra is the passage that carries urine from the urinary bladder through the penis to the outside. In males, it also carries semen during ejaculation.

4. What is the function of the acrosome?

Ans: The acrosome contains enzymes that help a sperm penetrate the coverings of the ovum.

5. Which hormone is secreted by Leydig cells?

Ans: Testosterone.

6. What is the main function of the epididymis?

Ans: It stores sperm temporarily and allows them to mature.

7. What are the main sugars present in seminal-vesicle fluid?

Ans: Fructose is the principal sugar; glucose may also be present in small amounts.

8. What are the main parts of the human female reproductive system?

Ans: A pair of ovaries, a pair of oviducts or fallopian tubes, the uterus, cervix, and vagina.

9. Which female sex hormone is secreted by the ovaries?

Ans: Oestrogen.

10. What happens to the corpus luteum if fertilisation does not occur?

Ans: It degenerates, hormone levels fall, and the uterine lining breaks down during menstruation.

11. What is the fallopian tube?

Ans: It is the tube that carries the ovum from the region of an ovary towards the uterus.

12. Name two major external regions of the uterus.

Ans: The body of the uterus and the cervix.

13. Which hormones are released by the anterior pituitary in response to GnRH?

Ans: Luteinising hormone (LH) and follicle-stimulating hormone (FSH).

14. What are the main parts of a sperm cell?

Ans: The head, middle piece, and tail; the neck connects the head and middle piece.

15. What is semen?

Ans: Semen is the mixture of sperm and secretions from the male reproductive accessory glands.

16. What does semen contain?

Ans: Sperm cells and seminal fluid containing secretions from the accessory glands.

17. Which cell organelles provide energy for sperm movement?

Ans: Mitochondria.

18. Which hormone is secreted by the corpus luteum?

Ans: Progesterone.

19. At what stage does meiosis begin in primary oocytes?

Ans: During foetal development, before birth.

20. Into which two regions is the cytoplasm of an ovum commonly described as divided?

Ans: The cortex (outer cytoplasm) and the endoplasm (inner cytoplasm).

21. Which gland secretes luteotrophic hormone?

Ans: The anterior pituitary gland; prolactin is also known as luteotrophic hormone in some contexts.

22. What is ovulation?

Ans: Ovulation is the release of a secondary oocyte from a mature ovarian follicle.

23. Which structure produces progesterone after ovulation?

Ans: The corpus luteum.

24. What is fertilisation?

Ans: Fertilisation is the fusion of a male gamete and a female gamete to form a zygote.

25. Name the two main cell populations in a blastocyst.

Ans: The trophoblast (outer cell layer) and the inner cell mass.

26. Where does fertilisation usually occur in humans?

Ans: Usually in the ampullary region of the fallopian tube.

27. What is sperm capacitation?

Ans: Capacitation is a series of changes sperm undergo in the female reproductive tract that enable them to fertilise an ovum.

28. What is cleavage?

Ans: Cleavage is the series of rapid mitotic divisions of the zygote into smaller cells called blastomeres, without an overall increase in embryo size.

29. What is the placenta?

Ans: The placenta is a temporary organ that connects the developing foetus with the uterine wall and enables exchange between maternal and foetal blood.

30. What is menopause?

Ans: Menopause is the permanent cessation of menstruation, marking the end of the reproductive phase.

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B. Short-Answer Questions (Human Reproduction Solutions)

31. State two important points about the formation and development of ova.

Ans: Oogenesis begins before birth, when primary oocytes form in the foetal ovaries. After puberty, usually one oocyte completes maturation and is released during each ovulatory cycle; only a limited number of follicles ovulate during a person’s reproductive years.

32. What are Leydig cells? State their function.

Ans: Leydig cells are interstitial cells located between the seminiferous tubules of the testes. They synthesise and secrete testosterone, which supports male reproductive development and function.

33. What is the fallopian tube? Describe its main features.

Ans: The fallopian tube carries the oocyte from the ovary towards the uterus. Its funnel-shaped infundibulum bears fimbriae, and its ciliated lining helps move the oocyte. Fertilisation usually occurs in the ampulla.

34. Describe the structure of the human ovum.

Ans: The human ovum is a large, spherical cell with abundant cytoplasm and a haploid nucleus. It is surrounded by the plasma membrane, the zona pellucida, and an outer layer of follicular cells called the corona radiata.

35. What changes occur in the female body during the follicular phase of the menstrual cycle?

Ans: FSH stimulates ovarian follicles to grow and one usually becomes dominant. The developing follicles secrete oestrogen, which helps rebuild and thicken the endometrium after menstruation.

36. What is fertilisation? Briefly describe the process in humans.

Ans: Fertilisation is the fusion of a sperm and a secondary oocyte to form a diploid zygote. In humans, sperm travel through the female reproductive tract and fertilisation usually occurs in the ampulla of the fallopian tube.

37. Write the main characteristics of cleavage.

Ans: Cleavage consists of rapid mitotic divisions of the zygote. The daughter cells, called blastomeres, become progressively smaller; the embryo’s overall size does not increase appreciably, and the divisions lead to the morula and then the blastocyst.

38. Describe the structure of a blastocyst.

Ans: A blastocyst is a hollow, early embryonic stage. It has an outer trophoblast, an inner cell mass at one side, and a fluid-filled cavity called the blastocoel. The trophoblast contributes to extra-embryonic structures, including the foetal part of the placenta, while the inner cell mass forms the embryo.

39. State the functions of progesterone.

Ans: Progesterone prepares and maintains the endometrium for implantation and pregnancy. It helps reduce uterine contractions and supports the continuation of pregnancy.

40. Justify the statement: “The placenta acts as an endocrine tissue.”

Ans: The placenta secretes hormones, including human chorionic gonadotropin (hCG), human placental lactogen (hPL), oestrogens, and progesterone. These hormones help maintain pregnancy and support foetal growth and maternal physiological changes.

41. Differentiate between morula and blastula/blastocyst.

Ans: Morula: a solid ball of blastomeres with no central cavity. Blastula/blastocyst: a later stage with a fluid-filled cavity; in mammals it has an outer trophoblast and an inner cell mass.

42. Mention the main functions of the placenta.

Ans: The placenta transfers oxygen and nutrients from the mother to the foetus, removes carbon dioxide and metabolic wastes from foetal blood, produces pregnancy-supporting hormones, and provides a selective barrier between maternal and foetal circulations.

43. Draw and label a sperm cell.

Ans: Label the following parts in a diagram: head (nucleus and acrosome), neck, middle piece (mitochondria), and tail or flagellum.

44. What is colostrum? State its importance.

Ans: Colostrum is the first milk produced in the first few days after childbirth. It is rich in antibodies and other protective substances and helps protect the newborn against infections.

45. What is parturition?

Ans: Parturition is the process of childbirth. Hormonal and nervous signals lead to strong, rhythmic uterine contractions that help expel the fully developed foetus through the birth canal.

46. Draw and label the human female reproductive system.

Ans: Label the ovaries, fimbriae, infundibulum, fallopian tubes (oviducts), uterus, cervix, and vagina.

C. Descriptive Questions (3–5 Marks Each)

47. Describe the structure of a human sperm cell.

Ans: A sperm cell has a head, neck, middle piece, and tail. The head contains a haploid nucleus and an acrosome, whose enzymes help the sperm penetrate the ovum’s coverings. The neck contains centrioles. The middle piece contains mitochondria arranged around the axial filament and supplies energy for movement. The tail is a flagellum that propels the sperm.

48. Briefly describe the layers of the uterine wall.

Ans: The uterine wall has three layers. The outer perimetrium is a protective serous covering. The middle myometrium consists of smooth muscle and contracts strongly during childbirth. The inner endometrium is a glandular mucosal lining that changes during the menstrual cycle and is the site of implantation.

49. What is the reproductive cycle? Describe the main phases of the menstrual cycle.

Ans: The reproductive cycle refers to recurring changes in the ovaries and uterus that prepare the body for possible pregnancy. The main phases are: (i) Follicular phase: FSH promotes follicle growth and oestrogen rebuilds the endometrium. (ii) Ovulation: a mature follicle releases the secondary oocyte, usually near the middle of the cycle. (iii) Luteal phase: the corpus luteum secretes progesterone and some oestrogen, maintaining the endometrium. (iv) Menstrual phase: if pregnancy does not occur, the corpus luteum regresses, hormone levels fall, and the endometrial lining is shed.

50. Describe the process of parturition in humans.

Ans: Parturition is the birth of the fully developed foetus at the end of pregnancy. Signals from the foetus and placenta help initiate mild uterine contractions. These promote the release of oxytocin from the maternal posterior pituitary. Oxytocin intensifies uterine contractions, which in turn stimulate further oxytocin release. This positive-feedback process strengthens contractions until the baby is expelled through the birth canal.

51. Describe blastulation or the formation of a blastocyst.

Ans: After cleavage, the embryo forms a morula. Fluid then enters the embryo and creates a cavity called the blastocoel. Cells become organised into an outer trophoblast and an inner cell mass, forming a blastocyst. The zona pellucida is shed before implantation. The inner cell mass develops into the embryo, while the trophoblast contributes to the foetal part of the placenta and other supporting tissues.

52. Describe the human female reproductive system.

Ans: The female reproductive system lies mainly in the pelvic cavity and includes a pair of ovaries, a pair of fallopian tubes, the uterus, cervix, vagina, and external genitalia. The ovaries produce oocytes and secrete hormones such as oestrogen and progesterone. Each fallopian tube has an infundibulum with fimbriae, an ampulla, and a narrower uterine part; it carries the oocyte and is the usual site of fertilisation. The uterus is a muscular, pear-shaped organ where implantation and foetal development occur. Its lower narrow part, the cervix, opens into the vagina, which serves as the birth canal and receives sperm during intercourse.

53. Describe foetal development from the first to the ninth month of pregnancy.

Ans: During the first month, early embryonic structures and the developing heart begin to form. By the end of the second month, the limbs and digits become more distinct. By the end of the third month, most major body organs have begun to form. Around the fifth month, foetal movements are commonly felt and hair begins to appear. During the sixth and seventh months, the foetus grows, the eyelids open, and eyelashes develop; survival outside the uterus may be possible with intensive medical care if birth occurs very prematurely. During the eighth and ninth months, organs continue to mature, body mass increases, and the foetus usually assumes a position suitable for birth.

D. Additional Questions and Answers (Human Reproduction Solutions)

1. What is an early sign of pregnancy?

Ans: A missed menstrual period is a common early sign of pregnancy, although it can have other causes and is not conclusive by itself.

2. When does a zygote begin to divide and develop?

Ans: Cleavage begins soon after fertilisation as the zygote travels through the fallopian tube, before the blastocyst implants in the uterus.

3. When does spermatogenesis begin?

Ans: Spermatogenesis begins at puberty.

4. What is the inguinal canal?

Ans: The inguinal canal is a short passage in the lower abdominal wall. In males, it provides a route for the spermatic cord and is associated with the descent of the testes into the scrotum.

5. What is colostrum?

Ans: Colostrum is the first secretion of the mammary glands after childbirth. It is especially rich in protective antibodies and helps provide early immune protection to the newborn.

6. State the function of the Bartholin glands in females.

Ans: The Bartholin glands secrete mucus near the vaginal opening, helping lubricate the area, especially during sexual arousal.

7. Briefly describe the structure of the uterine wall.

Ans: The uterine wall has three layers: the outer perimetrium, the muscular middle myometrium, and the inner glandular endometrium. The endometrium changes cyclically and supports implantation; the myometrium contracts during labour.

8. Mention the main functions of the male accessory ducts and glands.

Ans: The epididymis stores and matures sperm; the vasa deferentia transport sperm; and the ejaculatory ducts and urethra conduct semen towards the outside. The seminal vesicles, prostate gland, and bulbourethral glands add fluids that nourish, protect, and lubricate sperm and form seminal fluid.

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