આ MCQ મોડ્યુલ આના પર આધારિત છે: NCERT Exercises and Solutions: Human Reproduction
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NCERT Exercises and Solutions: Human Reproduction
🎓 Class 12
Biology
CBSE
Theory
Ch 2 – Human Reproduction
⏱ ~8 min
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આ મૂલ્યાંકન આના પર આધારિત હશે: NCERT Exercises and Solutions: Human Reproduction
મૂલ્યાંકન બનાવવામાં તેમની સામગ્રી સામેલ કરવા ચિત્રો, PDF અથવા Word દસ્તાવેજ અપલોડ કરો.
Chapter 2 — Human Reproduction (Part 5): Summary & NCERT Exercises
This final part consolidates the chapter with a structured summary, key terms, an interactive review, and worked solutions to the NCERT exercises from Chapter 2 — Human Reproduction.
3.9 Chapter Summary
Male System
Testes (in scrotum) → seminiferous tubules contain spermatogonia & Sertoli cells; interstitium has Leydig cells. Accessory ducts: rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra. Glands: seminal vesicles, prostate, bulbourethral. Semen = sperm + glandular secretions.
Female System
Ovaries (paired) + fallopian tubes (infundibulum/fimbriae, ampulla, isthmus) + uterus (peri-, myo-, endometrium) + cervix + vagina + mammary glands. Ovary cortex contains follicles at various stages.
Menstrual Cycle (28 d)
4 phases: Menstrual (1-5) — endometrium shed; Follicular (6-13) — FSH ↑, estrogen ↑; Ovulatory (~14) — LH surge; Luteal (15-28) — corpus luteum, progesterone ↑. Menarche at puberty; menopause ~50 y.
Gametogenesis
Spermatogenesis: 1 spermatocyte → 4 sperms; spermiogenesis; spermiation. Oogenesis: begins in foetus; primary oocyte arrests at prophase I; gives 1 ovum + 3 polar bodies; meiosis II completes only on fertilisation.
Fertilisation & Cleavage
Site: ampullary-isthmic junction. Acrosome enzymes pierce zona pellucida; one sperm only (cortical reaction). Zygote (2n) → cleavage → morula → blastocyst (trophoblast + inner cell mass) → implantation (Day 6-7).
Pregnancy & Birth
Placenta + chorionic villi + umbilical cord. Hormones: hCG, hPL, estrogens, progesterone, relaxin. 3 trimesters (~9 months). Parturition: foetal ejection reflex → oxytocin positive feedback → birth. Lactation: prolactin makes milk; colostrum = first milk rich in IgA antibodies.
3.10 Key Terms — Quick Reference
Interactive Review: Identify the Stage
Click each pathway step to see the structure produced.
Ovulation (Day 14): Graafian follicle ruptures and releases the secondary oocyte into the fallopian tube. Triggered by the LH surge.
3.11 NCERT Exercises — Worked Solutions
Q1. Fill in the blanks: L1 Remember
(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 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) Fertilisation takes place in the ___.
(j) Zygote divides to form ___ which is implanted in uterus.
(k) The structure which provides vascular connection between the foetus and uterus is called ___.
(a) sexually, (b) viviparous, (c) internal, (d) haploid, (e) diploid, (f) ovulation, (g) Luteinising Hormone (LH), (h) fertilisation/syngamy, (i) ampullary-isthmic junction of fallopian tube, (j) blastocyst, (k) placenta.
Q2. Draw a labelled diagram of male reproductive system. L2 Understand
The male reproductive system consists of paired testes (in scrotum), accessory ducts (rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct, urethra), accessory glands (seminal vesicles, prostate, bulbourethral glands) and the penis.
Q3. Draw a labelled diagram of female reproductive system. L2 Understand
The female reproductive system comprises a pair of ovaries, oviducts (fallopian tubes), uterus, cervix, vagina, external genitalia and a pair of mammary glands.
Q4. Write two major functions each of testis and ovary. L2 Understand
Testis: (i) Produces male gametes (sperms) by spermatogenesis. (ii) Synthesises and secretes androgens (testosterone) by Leydig cells.
Ovary: (i) Produces female gametes (ova) by oogenesis. (ii) Secretes the female sex steroid hormones — estrogens (from the growing follicle) and progesterone (from the corpus luteum).
Ovary: (i) Produces female gametes (ova) by oogenesis. (ii) Secretes the female sex steroid hormones — estrogens (from the growing follicle) and progesterone (from the corpus luteum).
Q5. Describe the structure of seminiferous tubule. L2 Understand
The seminiferous tubule is the site of sperm production. Each tubule is lined on its inside by two types of cells: (i) male germ cells (spermatogonia) which divide and differentiate into sperms, and (ii) Sertoli cells (nurse cells) which provide nutrition to the developing germ cells. The tubule is surrounded by interstitial spaces containing blood vessels and clusters of Leydig cells (interstitial cells) that secrete testicular androgens. Mature sperms are released into the lumen and pass into the rete testis.
Q6. What is spermatogenesis? Briefly describe the process of spermatogenesis. L2 Understand
Spermatogenesis is the process by which immature male germ cells (spermatogonia) form sperms inside the seminiferous tubules. Steps:
- Diploid spermatogonia (2n) multiply by mitosis.
- Some enlarge to form primary spermatocytes (2n) which undergo Meiosis I to form two haploid secondary spermatocytes (n).
- Each secondary spermatocyte undergoes Meiosis II to form two spermatids — total 4 spermatids per primary spermatocyte.
- Spermatids transform into mature sperms by spermiogenesis.
- Mature sperms are released from Sertoli cells (spermiation) into the lumen.
Q7. Name the hormones involved in regulation of spermatogenesis. L1 Remember
GnRH (hypothalamus) → FSH and LH (anterior pituitary). LH stimulates Leydig cells to produce testosterone. FSH acts on Sertoli cells, stimulating release of factors that aid spermiogenesis. Testosterone is the principal driver of spermatogenesis.
Q8. Define spermiogenesis and spermiation. L1 Remember
Spermiogenesis — transformation of round spermatids into elongated, motile sperms (development of acrosome, condensation of nucleus, formation of middle piece with mitochondria, and tail).
Spermiation — release of mature sperms from Sertoli cells into the lumen of the seminiferous tubule.
Spermiation — release of mature sperms from Sertoli cells into the lumen of the seminiferous tubule.
Q9. Draw a labelled diagram of sperm. L2 Understand
Q10. What are the major components of seminal plasma? L1 Remember
Seminal plasma is the fluid component of semen contributed by accessory glands. It is rich in fructose (energy for sperm), calcium, certain enzymes, ascorbic acid, and is slightly alkaline. Seminal vesicles contribute fructose; the prostate provides citric acid and enzymes; bulbourethral glands provide lubricating mucus.
Q11. What are the major functions of the male accessory ducts and glands? L2 Understand
Accessory ducts (rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct, urethra) store and transport sperms from the testis to the urethral opening.
Accessory glands (seminal vesicles, prostate, bulbourethral) provide secretions that nourish, activate and lubricate sperms — fructose for energy, alkaline medium to neutralise vaginal acidity, and mucus for lubrication.
Accessory glands (seminal vesicles, prostate, bulbourethral) provide secretions that nourish, activate and lubricate sperms — fructose for energy, alkaline medium to neutralise vaginal acidity, and mucus for lubrication.
Q12. What is oogenesis? Give a brief account of oogenesis. L2 Understand
Oogenesis is the formation of mature ovum in the ovary. It begins during foetal life: about 2 million oogonia form in each foetal ovary; no further oogonia appear after birth. Oogonia enter prophase I and arrest as primary oocytes. Each is enclosed by granulosa cells to form a primary follicle. Many degenerate; ~60-80,000 remain at puberty.
Each cycle, the primary follicle grows into a secondary, then tertiary, then Graafian follicle. Meiosis I completes (unequally) just before ovulation, producing a large secondary oocyte (n) and a tiny first polar body. The Graafian follicle ruptures (ovulation). Meiosis II completes only after fertilisation, yielding the haploid ovum and a second polar body.
Each cycle, the primary follicle grows into a secondary, then tertiary, then Graafian follicle. Meiosis I completes (unequally) just before ovulation, producing a large secondary oocyte (n) and a tiny first polar body. The Graafian follicle ruptures (ovulation). Meiosis II completes only after fertilisation, yielding the haploid ovum and a second polar body.
Q13. Draw a labelled diagram of a section through ovary. L2 Understand
A section of ovary shows: outer cortex (with follicles in various stages — primary, secondary, tertiary, Graafian) and inner medulla. After ovulation, the empty follicle becomes the corpus luteum.
Q14. Draw a labelled diagram of a Graafian follicle. L2 Understand
Q15. Name the functions of the following: (a) corpus luteum (b) endometrium (c) acrosome (d) sperm tail (e) fimbriae. L1 Remember
(a) Corpus luteum — secretes progesterone, maintaining the endometrium for possible implantation.
(b) Endometrium — provides the bed for implantation of the blastocyst and supports placental development.
(c) Acrosome — contains hydrolytic enzymes that digest the zona pellucida, enabling sperm to penetrate the ovum.
(d) Sperm tail — provides motility, propelling the sperm towards the ovum.
(e) Fimbriae — finger-like processes of the infundibulum that capture the released ovum and direct it into the fallopian tube.
(b) Endometrium — provides the bed for implantation of the blastocyst and supports placental development.
(c) Acrosome — contains hydrolytic enzymes that digest the zona pellucida, enabling sperm to penetrate the ovum.
(d) Sperm tail — provides motility, propelling the sperm towards the ovum.
(e) Fimbriae — finger-like processes of the infundibulum that capture the released ovum and direct it into the fallopian tube.
Q16. Identify True / False statements. Correct each false statement. L2 Understand
(a) Androgens are produced by Sertoli cells.
(b) Spermatozoa get nutrition from Sertoli cells.
(c) Leydig cells are found in ovary.
(d) Leydig cells synthesise androgens.
(e) Oogenesis takes place in corpus luteum.
(f) Menstrual cycle ceases during pregnancy.
(g) Presence or absence of hymen is not a reliable indicator of virginity or sexual experience.
(a) False — androgens are produced by Leydig (interstitial) cells, not Sertoli cells.
(b) True.
(c) False — Leydig cells are found in the testis (interstitial spaces), not in the ovary.
(d) True.
(e) False — oogenesis occurs in the ovarian cortex (within follicles), not in the corpus luteum.
(f) True.
(g) True.
(b) True.
(c) False — Leydig cells are found in the testis (interstitial spaces), not in the ovary.
(d) True.
(e) False — oogenesis occurs in the ovarian cortex (within follicles), not in the corpus luteum.
(f) True.
(g) True.
Q17. What is menstrual cycle? Which hormones regulate the menstrual cycle? L2 Understand
The menstrual cycle is the cyclical reproductive cycle in female primates of about 28 days, beginning at puberty (menarche) and ending at menopause. It has four phases: menstrual (1-5), follicular (6-13), ovulatory (~14), and luteal (15-28). One ovum is released mid-cycle.
Regulating hormones: FSH stimulates follicular growth; estrogen proliferates the endometrium and helps trigger the LH surge; the mid-cycle LH surge induces ovulation; progesterone from the corpus luteum maintains the secretory endometrium. If no pregnancy, progesterone falls and menstruation begins.
Regulating hormones: FSH stimulates follicular growth; estrogen proliferates the endometrium and helps trigger the LH surge; the mid-cycle LH surge induces ovulation; progesterone from the corpus luteum maintains the secretory endometrium. If no pregnancy, progesterone falls and menstruation begins.
Q18. What is parturition? Which hormones are involved in induction of parturition? L2 Understand
Parturition is the process of childbirth — vigorous uterine contractions that expel the developed foetus through the birth canal. It is induced by a complex neuroendocrine mechanism. The fully developed foetus and the placenta send signals (foetal ejection reflex) that trigger release of oxytocin from the maternal posterior pituitary. Oxytocin causes powerful uterine contractions, which intensify oxytocin release in a positive-feedback loop. Relaxin from the placenta softens the cervix and pelvic ligaments, easing delivery. Estrogens promote uterine sensitivity to oxytocin near term.
Q19. In our society the women are often blamed for giving birth to daughters. Can you explain why this is not correct? L5 Evaluate
The mother is XX and produces only X-bearing ova. The father is XY and produces sperms in two types — X-bearing and Y-bearing. Whether the embryo becomes a girl (XX) or a boy (XY) depends entirely on which sperm fertilises the ovum. Therefore the sex of the child is determined by the father's chromosome contribution, not the mother. Blaming the woman for the sex of the child is biologically incorrect and socially unjust.
Q20. How many eggs are released by a human ovary in a month? How many eggs would have been released if the mother gave birth to 5 children in her reproductive period? (Assume no other pregnancies.) L3 Apply
Normally, only one egg is released per menstrual cycle (one per month) — alternately by the two ovaries.
A typical reproductive lifespan is from ~13 (menarche) to ~50 years (menopause) ≈ 37 years × 12 cycles = ~444 months. During each pregnancy (~9 months) ovulation is suspended.
For 5 children: 5 × 9 = 45 months without ovulation. So eggs released = 444 - 45 = ~399 eggs. (Approximate, ignoring lactational amenorrhoea and irregular cycles.)
A typical reproductive lifespan is from ~13 (menarche) to ~50 years (menopause) ≈ 37 years × 12 cycles = ~444 months. During each pregnancy (~9 months) ovulation is suspended.
For 5 children: 5 × 9 = 45 months without ovulation. So eggs released = 444 - 45 = ~399 eggs. (Approximate, ignoring lactational amenorrhoea and irregular cycles.)
Q21. What are the major events during fertilisation? L2 Understand
(i) Sperm reach the ampullary-isthmic junction. (ii) Sperm contacts the zona pellucida; acrosomal enzymes (e.g., hyaluronidase) digest the corona radiata and zona pellucida. (iii) The first sperm penetrates the plasma membrane of the ovum; cortical reaction blocks polyspermy. (iv) Sperm entry triggers completion of meiosis II → ovum + second polar body. (v) Haploid male and female pronuclei fuse → diploid zygote. (vi) Sex of the embryo is decided by the sperm's sex chromosome (X or Y).
Q22. Write short notes on (a) capacitation, (b) cleavage, (c) parturition, (d) implantation. L2 Understand
(a) Capacitation — physiological maturation of sperms in the female reproductive tract that gives them the ability to fertilise the ovum. Membrane modifications enable the acrosomal reaction.
(b) Cleavage — rapid mitotic divisions of the zygote (without growth) producing 2, 4, 8, 16 blastomeres → morula → blastocyst.
(c) Parturition — expulsion of the fully developed foetus from the uterus, induced by oxytocin via positive feedback.
(d) Implantation — embedding of the trophoblast of the blastocyst into the secretory endometrium of the uterus, around day 6-7 after fertilisation; establishes pregnancy.
(b) Cleavage — rapid mitotic divisions of the zygote (without growth) producing 2, 4, 8, 16 blastomeres → morula → blastocyst.
(c) Parturition — expulsion of the fully developed foetus from the uterus, induced by oxytocin via positive feedback.
(d) Implantation — embedding of the trophoblast of the blastocyst into the secretory endometrium of the uterus, around day 6-7 after fertilisation; establishes pregnancy.
Activity 3.5 — Self-Quiz
Predict: Where does fertilisation take place? Which hormone triggers ovulation? What is the first milk called? What hormone induces parturition?
Observe: (i) Ampullary-isthmic junction of fallopian tube. (ii) LH surge. (iii) Colostrum. (iv) Oxytocin.
Explain: Mastery of these four facts unlocks much of the chapter — site of fertilisation, ovulation trigger, immune-rich first milk, and the contraction hormone of childbirth.
Mixed Competency-Based Questions
Q1. The site of fertilisation in humans is: L1 Remember
(a) Cervix (b) Uterus (c) Ampullary-isthmic junction (d) Vagina
(a) Cervix (b) Uterus (c) Ampullary-isthmic junction (d) Vagina
(c) Ampullary-isthmic junction of the fallopian tube.
Q2. A 16-cell solid ball produced by cleavage is called: L1 Remember
A morula. It later forms a hollow blastocyst.
Q3. Distinguish menarche from menopause. L2 Understand
Menarche is the first menstruation occurring at puberty (~12-14 years), marking the onset of reproductive capability. Menopause is the cessation of menstrual cycles around 50 years of age, marking the end of reproductive capability.
Q4. Imagine a drug that blocks LH receptors in the ovary. Predict its effect on the menstrual cycle. L3 Apply
Blocking LH receptors prevents the LH surge from acting on the Graafian follicle → no ovulation. Without ovulation, no corpus luteum forms → no progesterone surge → endometrium does not become secretory; the cycle becomes anovulatory and pregnancy is impossible. (Such drugs are used as emergency contraceptives.)
Q5. Justify the design statement: "The placenta is both a barrier and a bridge." L5 Evaluate
The placenta is a bridge — chorionic villi exchange O₂, nutrients and waste between maternal and foetal blood, and produce hormones (hCG, hPL, estrogens, progesterone, relaxin) that maintain pregnancy. It is also a barrier — maternal and foetal blood do not normally mix; the placenta filters out many pathogens, large molecules and antibodies, protecting the foetus. This dual role makes it uniquely suited to support intrauterine development.
Assertion–Reason Questions
Q1. Assertion (A): The sex of a child is determined by the father.
Reason (R): Sperms are of two types — X- or Y-bearing, while ova carry only X.
Reason (R): Sperms are of two types — X- or Y-bearing, while ova carry only X.
(A) Both true; R correctly explains A.
Q2. Assertion (A): Meiosis II of the secondary oocyte completes only after fertilisation.
Reason (R): Sperm entry triggers the calcium signal that resumes the cell cycle.
Reason (R): Sperm entry triggers the calcium signal that resumes the cell cycle.
(A) Both true; R correctly explains A.
Q3. Assertion (A): Colostrum is the milk produced in the last trimester.
Reason (R): Colostrum is rich in IgA antibodies that protect the newborn.
Reason (R): Colostrum is rich in IgA antibodies that protect the newborn.
(D) A is false (colostrum is the milk produced in the first few days after delivery); R is true.
Frequently Asked Questions - NCERT Exercises and Solutions: Human Reproduction
What are the most-asked NCERT exercise questions in Chapter Human Reproduction?
NCERT Class 12 Biology Chapter on Human Reproduction exercises cover definitions, mechanisms, labelled diagrams, comparison tables, and application-based questions. The MyAiSchool solution set provides full step-by-step solutions for every NCERT question, aligned with the CBSE board exam pattern. Students should master scientific terminology, mechanism flowcharts, and concept comparison to score full marks.
How should students approach diagram-based questions in Human Reproduction?
For diagram-based questions in NCERT Class 12 Biology Chapter on Human Reproduction: (1) draw clean, proportional, large diagrams with sharp pencil lines, (2) label all parts horizontally on the right side using a ruler, (3) use scientific terminology (Latin/Greek names where applicable), (4) write a 1-2 line description if asked. The MyAiSchool solutions provide editable reference diagrams aligned with NCERT textbook figures.
What types of CBSE board questions come from Human Reproduction?
CBSE Class 12 Biology board questions from Human Reproduction typically include: (1) 1-mark MCQs on definitions and processes, (2) 2-mark short-answer mechanism/comparison questions, (3) 3-mark labelled-diagram questions, (4) 5-mark long-answer essays combining mechanism + diagram + significance. The MyAiSchool exercise set tags each question by mark weight and Bloom level (L1-L6).
How do I compare two biological processes in 5-mark questions?
For 5-mark comparison questions in NCERT Class 12 Biology on Human Reproduction: (1) use a two-column table with feature headings down the left side, (2) compare on at least 5-6 features (definition, location, mechanism, control, outcome, significance), (3) include one labelled diagram if relevant, (4) end with biological significance. The MyAiSchool solutions follow this CBSE-aligned tabular format consistently for full marks.
What are common mistakes in Human Reproduction exercises?
Common mistakes in NCERT Class 12 Biology Human Reproduction include: (1) confusing similar terms (mitosis vs meiosis, syngamy vs triple fusion, etc.), (2) skipping intermediate steps in mechanisms, (3) missing examples or species names, (4) writing essays when tables are expected, (5) forgetting biological significance. The MyAiSchool solutions highlight these traps with red flags so students avoid losing marks.
How does the MyAiSchool solution differ from other NCERT solution sets?
MyAiSchool Class 12 Biology Human Reproduction solutions use NEP 2024-aligned pedagogy with Bloom Taxonomy tagged questions (L1 Remember to L6 Create), step-by-step working with biological reasoning, fully labelled SVG diagrams, comparison tables, interactive simulations, and Competency-Based Questions (CBQs) for board exam practice. Each solution is verified against NCERT and CBSE marking schemes.
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