🌸 Chapter 2
Human Reproduction
(5 Marks )
🌸 Human Reproduction – 5
Marks Questions with Answers
1. Describe the structure and
function of the male reproductive system.
Answer:
- Primary sex organ: Testes – produce sperm and
testosterone.
- Accessory ducts: Epididymis, vas deferens,
ejaculatory duct, and urethra – transport and mature sperm.
- Glands: Seminal vesicles (secrete
fructose), prostate (milky fluid), and bulbourethral glands (lubrication).
- External genitalia: Penis – delivers sperm;
scrotum – maintains testicular temperature.
Function: Together, they produce, mature, and deliver sperm for fertilization.
2. Describe the structure and
function of the female reproductive system.
Answer:
- Ovaries: Produce ova and hormones
(estrogen and progesterone).
- Fallopian tubes: Transport ova; site of
fertilization.
- Uterus: Site of implantation and fetal
development.
- Cervix & vagina: Facilitate sperm entry and
childbirth.
Function: Production of ova, fertilization, and nurturing of embryo.
3. Explain the structure of a mature
human sperm.
Answer:
- Head: Contains haploid nucleus and
acrosome (with enzymes for egg penetration).
- Neck: Contains centrioles.
- Middle piece: Mitochondria for energy.
- Tail: Flagellum for motility.
Function: To deliver male genetic material to the ovum.
4. Explain the structure of a human
ovum.
Answer:
- Spherical cell, non-motile,
surrounded by zona pellucida and corona radiata.
- Contains haploid nucleus
and cytoplasm rich in nutrients.
Function: Carries female genetic material and supports early zygote formation.
5. Explain the process of
spermatogenesis.
Answer:
- Occurs in seminiferous
tubules.
- Spermatogonia → Primary spermatocyte
→ Secondary spermatocyte → Spermatid → Spermatozoa.
- Sertoli cells provide nourishment; Leydig
cells secrete testosterone.
Function: Production of haploid, motile sperms.
6. Explain the process of oogenesis.
Answer:
- Begins before birth: oogonia →
primary oocytes (arrested in prophase I).
- After puberty: primary oocyte
completes meiosis I → secondary oocyte + polar body.
- After fertilization: meiosis II
completes to form ovum and second polar body.
Result: One ovum and three polar bodies are formed.
7. Describe the role of hormones in
the menstrual cycle.
Answer:
- FSH: Stimulates follicle growth.
- LH: Triggers ovulation and corpus
luteum formation.
- Estrogen: Rebuilds endometrium.
- Progesterone: Maintains endometrium.
Cycle: Follicular → Ovulation → Luteal → Menstrual phase.
8. Explain the phases of the
menstrual cycle.
Answer:
1.
Menstrual
Phase (1–5 days):
Shedding of endometrium.
2.
Follicular
Phase (6–14):
Follicle growth, estrogen rise.
3.
Ovulation
(14th day):
LH surge releases egg.
4.
Luteal
Phase (15–28):
Corpus luteum secretes progesterone.
If no fertilization, cycle repeats.
9. Explain the process of
fertilization in humans.
Answer:
- Occurs in ampulla of
fallopian tube.
- Sperm penetrates corona radiata
and zona pellucida.
- Acrosomal reaction releases enzymes.
- Sperm and egg nuclei fuse → zygote
(diploid).
Significance: Restores diploid chromosome number.
10. Describe the process of
implantation.
Answer:
- Zygote divides to form
blastocyst.
- Reaches uterus after 5–7 days.
- Blastocyst attaches to
endometrium (implantation).
- Trophoblast cells secrete enzymes for embedding.
Result: Establishment of pregnancy.
11. Describe the stages of embryonic
development up to gastrulation.
Answer:
- Cleavage: Zygote → 2, 4, 8, 16 cells →
Morula.
- Blastulation: Morula → Blastocyst.
- Implantation: Blastocyst embeds in uterine
wall.
- Gastrulation: Formation of three germ layers
(ectoderm, mesoderm, endoderm).
12. What is placenta? Describe its
functions.
Answer:
- Placenta forms from chorionic
villi and maternal tissue.
Functions:
1.
Exchange
of gases and nutrients.
2.
Removes
fetal waste.
3.
Secretes
hormones: hCG, estrogen, progesterone, hPL.
4.
Provides
immunity.
5.
Acts
as barrier to some harmful substances.
13. Describe the role of hormones
during pregnancy.
Answer:
- hCG: Maintains corpus luteum.
- Progesterone & Estrogen: Maintain endometrium, inhibit
ovulation.
- hPL: Promotes fetal growth and
maternal metabolism.
- Relaxin: Softens pelvic ligaments for
childbirth.
14. Explain the process of
parturition.
Answer:
- Triggered by fetal ejection
reflex.
- Oxytocin released → uterine
contractions.
- Positive feedback between contractions
and oxytocin.
Stages: Dilation → Expulsion → Placental stage.
15. Explain lactation and colostrum.
Answer:
- Lactation: Milk secretion by mammary
glands post-childbirth.
- Stimulated by prolactin;
oxytocin aids ejection.
- Colostrum: First yellowish milk, rich in
antibodies – boosts infant immunity.
16. Explain the role of testes in
reproduction.
Answer:
- Produce sperm (exocrine
function).
- Secrete testosterone (endocrine
function).
Testosterone: Controls spermatogenesis, muscle growth, and secondary sexual characters.
17. Explain the role of ovary in
reproduction.
Answer:
- Produces ova and hormones.
- Estrogen: Controls female secondary
characters and endometrial growth.
- Progesterone: Maintains pregnancy.
18. What is the importance of
acrosomal reaction during fertilization?
Answer:
- Acrosome releases enzymes like hyaluronidase
and acrosin.
- Helps sperm penetrate zona
pellucida.
- Ensures species-specific
fertilization.
19. Explain gametogenesis and its
types.
Answer:
- Formation of gametes (haploid
cells) from germ cells.
- Spermatogenesis: In males; produces sperms.
- Oogenesis: In females; produces ovum.
Importance: Maintains chromosome number in species.
20. Explain hormonal control of
spermatogenesis.
Answer:
- GnRH (from hypothalamus): Stimulates pituitary.
- FSH: Acts on Sertoli cells →
spermatogenesis.
- LH: Stimulates Leydig cells →
testosterone.
- Testosterone: Promotes sperm maturation.
(… continuing in same pattern …)
Would you like me to continue from Question 21 to 50
(remaining 5-mark questions covering implantation, pregnancy hormones,
menstrual cycle disorders, IVF, test-tube baby, twins, contraception, and
NEET-based conceptual topics)?
It’ll include both Board-style and NEET-integrated 5-mark answers.
You said:
(… continuing in same pattern …)
ChatGPT said:
Perfect 👍 Here’s the continuation (Questions
21–50) of 5-mark questions with answers from Chapter – Human
Reproduction (Class 12 Biology, NCERT-based) — detailed for both CBSE
Board and NEET preparation.
🌸 Human Reproduction – 5
Marks Questions (21–50)
21. Describe the process of
implantation and its significance.
Answer:
- Implantation is the attachment
of the blastocyst to the uterine wall about 6–7 days after
fertilization.
- Process:
1.
Trophoblast
cells of the blastocyst secrete enzymes to erode uterine epithelium.
2.
Blastocyst
embeds into endometrium.
3.
Trophoblast
differentiates into cytotrophoblast and syncytiotrophoblast.
- Significance:
o Establishes connection between
mother and embryo.
o Leads to formation of the placenta.
o Marks beginning of pregnancy.
22. Explain the structure,
development, and functions of placenta.
Answer:
- Structure: Formed from chorionic villi
(fetal part) and uterine tissue (maternal part).
- Functions:
1.
Exchange
of nutrients and gases.
2.
Removal
of fetal waste.
3.
Secretion
of hormones – hCG, hPL, progesterone, estrogen.
4.
Acts
as barrier to harmful substances.
5.
Provides
passive immunity via maternal antibodies.
- Development: Begins after implantation;
fully formed by 12 weeks.
23. Describe the hormonal control of
the menstrual cycle.
Answer:
- FSH: Stimulates follicle growth.
- Estrogen: Rebuilds endometrium.
- LH: Surge causes ovulation.
- Progesterone: Maintains endometrium
post-ovulation.
- If fertilization fails →
progesterone & estrogen drop → menstruation occurs.
- Hormones are regulated by hypothalamus
(GnRH) → pituitary → ovaries feedback loop.
24. Explain the role of different
glands associated with male reproductive system.
Answer:
- Seminal vesicles: Secrete fructose (energy source)
and prostaglandins.
- Prostate gland: Adds milky fluid with enzymes
and calcium ions.
- Bulbourethral (Cowper’s)
glands:
Secrete mucus for lubrication and neutralization of urine residues.
Function: Secretions together form seminal plasma, enhancing sperm motility and fertility.
25. Describe the process of
fertilization and its physiological significance.
Answer:
- Fertilization: Union of sperm and ovum in
ampulla of fallopian tube.
- Steps:
1.
Sperm
capacitation.
2.
Acrosomal
reaction.
3.
Fusion
of gamete membranes.
4.
Completion
of meiosis II in ovum.
5.
Formation
of diploid zygote.
- Significance: Restores chromosome number and
initiates embryo formation.
26. Explain the hormonal changes
during pregnancy.
Answer:
- hCG: Maintains corpus luteum.
- Progesterone: Maintains endometrium,
prevents contractions.
- Estrogen: Promotes uterine growth and
breast development.
- hPL: Regulates maternal metabolism.
- Relaxin: Softens cervix for childbirth.
Combined effect: Ensure fetal development and preparation for parturition.
27. Describe the events of
parturition (childbirth).
Answer:
1.
Fetal
ejection reflex
stimulates oxytocin release.
2.
Oxytocin induces uterine contractions.
3.
Positive
feedback loop increases contraction intensity.
4.
Three
stages:
o Dilation stage – cervix opens.
o Expulsion stage – baby delivered.
o Afterbirth stage – placenta expelled.
Result: Delivery of baby and placenta safely.
28. Explain the process of lactation
and the importance of colostrum.
Answer:
- Lactation: Milk production by mammary
glands under prolactin and oxytocin.
- Colostrum: Yellowish first milk, rich in antibodies
(IgA) and nutrients.
Importance: Provides passive immunity and nutrition to newborn.
29. Explain gametogenesis with
suitable diagrams.
Answer:
- Spermatogenesis: Formation of haploid sperms
from spermatogonia.
- Oogenesis: Formation of haploid ovum from
oogonia.
Differences: Spermatogenesis produces 4 functional sperms; oogenesis produces 1 ovum and 3 polar bodies.
Importance: Maintains species’ chromosome number.
30. Describe the process of embryo
development up to blastocyst formation.
Answer:
- Zygote divides by cleavage → 2, 4,
8, 16-cell stages → Morula → Blastocyst.
- Blastocyst: Outer trophoblast, inner cell
mass, and fluid-filled cavity.
- Travels to uterus for
implantation.
Importance: Prepares for placental attachment and further differentiation.
31. What are the major events of the
menstrual cycle? Describe each.
Answer:
1.
Menstrual
phase: Shedding
of uterine lining.
2.
Follicular
phase: Follicle
growth, estrogen secretion.
3.
Ovulatory
phase: LH surge,
ovum release.
4.
Luteal
phase: Corpus
luteum secretes progesterone.
Cycle repeats if fertilization does not occur.
32. Compare spermatogenesis and
oogenesis.
Answer:
|
Feature |
Spermatogenesis |
Oogenesis |
|
Site |
Testes |
Ovaries |
|
Start |
Puberty |
Before birth |
|
End |
Continuous |
Menopause |
|
Product |
4 sperms |
1 ovum + 3 polar bodies |
|
Duration |
Continuous |
Cyclic |
|
Result: Both form haploid gametes essential for fertilization. |
33. Describe the structure and
function of a seminiferous tubule.
Answer:
- Structure: Lined by germinal epithelium
with spermatogenic and Sertoli cells.
- Interstitial (Leydig) cells lie
between tubules.
- Function:
- Site of sperm production.
- Sertoli cells nourish
developing sperms.
- Leydig cells secrete
testosterone.
34. What is the role of corpus
luteum in female reproductive physiology?
Answer:
- Formed from ruptured follicle
after ovulation.
- Secretes progesterone
and some estrogen.
- Maintains endometrium for
implantation.
- Degenerates into corpus
albicans if fertilization fails.
Importance: Ensures continuation or termination of menstrual cycle.
35. Explain the hormonal regulation
of male reproductive functions.
Answer:
- GnRH (Hypothalamus): Stimulates pituitary.
- FSH: Acts on Sertoli cells →
spermatogenesis.
- LH: Stimulates Leydig cells →
testosterone secretion.
- Testosterone: Maintains libido, secondary
sex characters, sperm production.
- Negative feedback via
testosterone inhibits GnRH and LH.
36. Explain the stages of embryonic
development in humans.
Answer:
- Zygote → Cleavage → Morula →
Blastocyst → Implantation → Gastrulation → Organogenesis.
- Embryo develops 3 germ layers:
ectoderm, mesoderm, endoderm.
Result: Formation of tissues and organs of the fetus.
37. How is pregnancy detected in
women?
Answer:
- Test: Detection of hCG (human chorionic
gonadotropin) in urine or blood.
- hCG is secreted by trophoblast
cells after implantation.
- Pregnancy test kits contain hCG
antibodies → color change indicates pregnancy.
38. Explain the physiological
changes in a woman during pregnancy.
Answer:
- Uterine enlargement, breast
development.
- Increased blood volume,
metabolic rate.
- Hormonal changes (rise in hCG,
progesterone, estrogen).
- Emotional and physical
adaptations for fetal growth.
39. What is gastrulation? Explain
its importance.
Answer:
- Process of forming three germ
layers: ectoderm, mesoderm, and endoderm.
- Occurs after implantation.
Importance: - Marks beginning of tissue and
organ formation.
- Differentiates body
structures.
40. Explain the significance of
reproductive hormones in males.
Answer:
- FSH: Sperm production.
- LH: Testosterone secretion.
- Testosterone: Growth of male organs,
spermatogenesis, and secondary characters.
Overall Role: Regulates sexual maturity and fertility.
41. Describe the role of hormones in
parturition.
Answer:
- Oxytocin: Triggers contractions.
- Relaxin: Relaxes pelvic ligaments.
- Estrogen & progesterone: Prepare uterus.
- Prostaglandins: Intensify contractions.
Mechanism: Positive feedback ensures complete delivery.
42. Explain IVF (Test Tube Baby)
technology.
Answer:
- Ova collected from mother →
fertilized with sperm in lab → zygote cultured → implanted in uterus.
Steps: Ovulation induction → Egg retrieval → Fertilization → Embryo transfer.
Uses: Helps infertile couples conceive.
43. What are identical and fraternal
twins?
Answer:
- Identical (Monozygotic): From one zygote → genetically
identical.
- Fraternal (Dizygotic): From two ova fertilized by two
sperms → genetically different.
Significance: Demonstrate natural reproductive variation.
44. Explain the role of pituitary
gland in reproduction.
Answer:
- FSH & LH control gamete formation and
hormone secretion.
- Prolactin: Milk production.
- Oxytocin: Uterine contraction and milk
ejection.
Coordination: Hypothalamic–pituitary–gonadal axis.
45. What is capacitation? Explain
its significance.
Answer:
- Physiological changes in sperm
inside female tract.
- Removes cholesterol and
proteins from membrane → acrosomal reaction possible.
Importance: Enables sperm to fertilize ovum.
46. Explain the process of cleavage
in human embryo.
Answer:
- Series of mitotic divisions in
zygote without growth.
- Produces morula and then
blastocyst.
- Occurs in fallopian tube.
Purpose: Increases cell number and prepares for implantation.
47. Explain the role of hormones in
lactation.
Answer:
- Prolactin: Initiates milk synthesis.
- Oxytocin: Causes milk ejection.
- Estrogen & progesterone: Prepare mammary glands during
pregnancy.
Feedback mechanism: Suckling stimulates milk secretion.
48. Explain how sex of the child is
determined in humans.
Answer:
- Female: XX; Male: XY.
- Female gamete always X; male
gamete either X or Y.
- If sperm contributes X → girl;
Y → boy.
Conclusion: Father determines sex of child.
49. Explain the role of progesterone
in reproduction.
Answer:
- Secreted by corpus luteum
and placenta.
- Maintains endometrium for
implantation.
- Inhibits uterine contraction.
- Prepares mammary glands for
lactation.
Essential hormone of pregnancy.
50. Describe any five common
reproductive disorders.
Answer:
1.
Amenorrhea: Absence of menstruation.
2.
Endometriosis: Growth of endometrial tissue
outside uterus.
3.
Infertility: Inability to conceive.
4.
Impotence: Inability to achieve erection.
5.
PCOS: Hormonal imbalance causing cysts in
ovaries.
Management: Hormonal therapy, surgery, or assisted reproduction.
