Human Reproduction — Class 12 MCQs with Answers

Human Reproduction — important questions & MCQs with answers (Class 12 Biology)

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   Site of sperm production:

   AAdrenalBProstateCLiverDTestis (seminiferous tubules)
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   Answer: Testis (seminiferous tubules)

   Explanation: Spermatogenesis — production of sperm from diploid spermatogonia — occurs inside the seminiferous tubules of the testis, not the epididymis, which only stores and matures sperm afterward.

2. Q2 of 6Easy

   The onset of the first menstruation at puberty is called:

   AGestationBMenopauseCOvulationDMenarche
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   Answer: Menarche

   Explanation: Menarche is the first menstrual cycle at puberty, marking the start of a female's reproductive phase; menopause, by contrast, marks its end decades later.

3. Q3 of 6Medium

   The transformation of spermatids into spermatozoa is called:

   ASpermiogenesisBSpermiationCSpermatogenesisDSpermatocytogenesis
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   Answer: Spermiogenesis

   Explanation: Spermiogenesis is the shaping of round spermatids into streamlined, motile spermatozoa; their eventual release into the tubule lumen is the separate step called spermiation.

4. Q4 of 6Medium

   Spermatogenesis is initiated by hormone:

   AFSH (follicle-stimulating hormone)BInsulinCAdrenalineDThyroxine
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   Answer: FSH (follicle-stimulating hormone)

   Explanation: FSH from the pituitary drives spermatogenesis by acting on Sertoli cells, while LH stimulates Leydig cells for testosterone; together the two gonadotropins regulate sperm production.

5. Q5 of 6Hard

   If a single primary spermatocyte and a single primary oocyte each complete gametogenesis, the total number of functional gametes produced is:

   A8B5C4D2
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   Answer: 5

   Explanation: One primary spermatocyte completes meiosis to give four functional sperm, but one primary oocyte's unequal division gives only one functional ovum — five gametes total, not equal numbers.

6. Q6 of 6Hard

   Implantation in humans typically occurs:

   A3 monthsBSame dayC30 daysD~6-7 days after fertilisation
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   Answer: ~6-7 days after fertilisation

   Explanation: The blastocyst reaches the uterus and implants about 6-7 days after fertilisation, not immediately — cleavage and travel through the oviduct take nearly a week.

Human Reproduction notes: key concepts (Class 12 Biology)

Human reproduction: the male and female reproductive systems, spermatogenesis and oogenesis, the hormone-driven menstrual cycle, fertilisation in the fallopian tube, cleavage to blastocyst and implantation, the placenta as an endocrine organ, and parturition and lactation.

Seminiferous tubules

Site of sperm formation in the testis; Sertoli cells nourish spermatids and secrete inhibin, while Leydig (interstitial) cells make testosterone.

Spermatogenesis

Formation of sperm from diploid spermatogonia via meiosis; one primary spermatocyte yields four sperms. Spermiogenesis reshapes spermatids into motile sperm.

Oogenesis

Formation of the ovum; begins in the foetus, arrests at prophase I, and one oogonium gives one ovum plus polar bodies (meiosis II ends at fertilisation).

Graafian follicle

The mature ovarian follicle that ruptures at ovulation to release the secondary oocyte; its remnant becomes the corpus luteum.

Menstrual cycle

~28-day cycle with menstrual, follicular, ovulatory and luteal phases; pituitary FSH/LH and ovarian estrogen/progesterone drive it.

Ovulation

Release of the secondary oocyte around day 14, triggered by a sharp mid-cycle LH surge acting on the mature Graafian follicle.

Corpus luteum

Formed from the ruptured follicle; secretes progesterone to maintain the endometrium. Degenerates to corpus albicans if no pregnancy occurs.

Fertilisation

Fusion of sperm and secondary oocyte in the ampulla of the fallopian tube; the acrosome reaction aids entry and the cortical reaction blocks polyspermy.

Blastocyst

After cleavage the morula (8-16 cells) forms a blastocyst with an outer trophoblast and an inner cell mass that becomes the embryo proper.

Implantation

Embedding of the blastocyst in the uterine endometrium about 7 days after fertilisation; the trophoblast attaches and helps form the placenta.

Placenta

Foeto-maternal organ for exchange of nutrients, gases and wastes; also endocrine, secreting hCG, hPL, estrogen, progesterone and relaxin.

hCG

Human chorionic gonadotropin from the trophoblast maintains the corpus luteum in early pregnancy; it is the hormone detected by home pregnancy tests.

Parturition

Childbirth driven by a neuroendocrine reflex; foetal-placental signals trigger oxytocin release, causing strong uterine contractions.

Lactation

Milk secretion by mammary glands after birth; prolactin drives it, and the first colostrum is rich in IgA antibodies giving the newborn passive immunity.