Solved Examples

This section is a dedicated worked-example set for the whole chapter — twelve solved questions spanning male and female reproductive anatomy, gametogenesis, the menstrual cycle, fertilisation, pregnancy and lactation, arranged from direct definitions to application and numerical reasoning.

Work through each question before reading its solution, and compare your phrasing with the NCERT-canonical wording used in the answers — that phrasing is what Board marking schemes reward. The Small Memory Capsule at the end compresses the chapter's most-quoted facts for quick revision.

Easy Tier — Direct Definitions and Recall

Q1: Define gametogenesis.

Answer: Gametogenesis = the process of formation of gametes (sperms in males, ova in females). Includes spermatogenesis (in testes) and oogenesis (in ovaries). Both involve mitosis + meiosis.

Q2: Where does spermatogenesis occur?

Answer: Spermatogenesis occurs INSIDE the seminiferous tubules of the testes. Specifically in the lining of the tubules, supported by Sertoli cells. Leydig cells (outside the tubules) produce testosterone.

Q3: Define ovulation.

Answer: Ovulation = the release of the secondary oocyte (still arrested in metaphase-II) from the Graafian follicle of the ovary; the fimbriae of the infundibulum then collect it into the fallopian tube. Triggered by the LH surge around day 14 of the menstrual cycle.

Q4: What is the menstrual cycle?

Answer: The menstrual cycle = the cyclical reproductive cycle in females, ~28 days long, characterised by predictable hormonal, ovarian, and uterine changes. Begins at menarche (~11-14 yr); ends at menopause (~50 yr). Prepares the body for potential pregnancy each month.

Q5: Define implantation.

Answer: Implantation = the attachment and embedding of the blastocyst into the endometrium of the uterus. Begins ~day 6-7 after fertilisation; completed by day 9-10. Marks the official start of pregnancy.

Q6: What is hCG?

Answer: hCG = human Chorionic Gonadotropin. Hormone produced by the trophoblast of the implanted blastocyst (later by the placenta). Functions: (1) maintains corpus luteum so progesterone continues, (2) basis of urinary pregnancy tests.

Q7: Define parturition.

Answer: Parturition = the process of childbirth — expulsion of the fully formed fetus from the mother's body at the end of pregnancy (~9 months). Initiated by the foetal ejection reflex (signals from the fully developed foetus and placenta), which triggers oxytocin release from the maternal pituitary, which causes uterine contractions.

Q8: What is colostrum?

Answer: Colostrum = the first milk produced by the mother for 2-3 days after childbirth. Yellowish, thick. Rich in IgA antibodies (passive immunity), proteins, vitamins. Critical for newborn defence against infections.

Q9: What is the function of fimbriae?

Answer: Fimbriae = finger-like projections of the infundibulum (funnel-shaped end of the fallopian tube near the ovary). Function: catch the released egg from the ovary and direct it into the fallopian tube.

Q10: Where does fertilisation occur?

Answer: Fertilisation occurs at the AMPULLARY-ISTHMIC JUNCTION of the fallopian tube (NCERT) — where the wide ampulla meets the narrow isthmus. Egg from ovary meets sperms swimming up from uterus. Within 24 hours of ovulation.

Medium Tier — Application + Numerical

Q11: A primary spermatocyte has 46 chromosomes. What is the chromosome count of a mature sperm?

Solution:

  • Primary spermatocyte (2n) = 46 chromosomes.
  • Meiosis halves the chromosome number.
  • Mature sperm (n) = 23 chromosomes.

Answer: 23 chromosomes.

Q12: If a primary oocyte has 46 chromosomes, how many chromosomes does the ovum have?

Solution:

  • Primary oocyte (2n) = 46 chromosomes.
  • Meiosis I produces secondary oocyte (n = 23).
  • Meiosis II produces ovum (n = 23).
  • (No further division of chromosome number.)

Answer: 23 chromosomes.

Small Memory Capsule

Section 14 patterns to master.

Top 10 most-asked Board topics (from this chapter)

  1. Anatomy of male/female reproductive systems — labelled diagrams
  2. Microscopic structure of testis (T.S.) — Sertoli + Leydig + germ cells
  3. Spermatogenesis — phases, ploidy, products (5-mark essay)
  4. Oogenesis — pre-natal initiation, two arrests, asymmetric division
  5. Menstrual cycle — 4 phases, hormones, LH surge
  6. Sperm structure — head, middle piece, tail
  7. Fertilisation events — capacitation, acrosomal reaction, cortical reaction
  8. Blastocyst structure — trophoblast vs ICM
  9. Placenta — structure + 5 functions
  10. Lactation — colostrum, prolactin, oxytocin

Answer-writing tips

  1. Always start with definition — captures 1 mark.
  2. Use NCERT-canonical phrases — examiners know them.
  3. Add diagrams — every 5-mark question deserves a labelled diagram.
  4. Show ploidy in gametogenesis questions.
  5. Use comparison tables for "distinguish between" questions.