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Human Reproduction – Class 12 Biology notes, important questions and MCQs

NCERT Class 12 Biology, chapter 2. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Humans reproduce sexually. Testes make sperm and ovaries make ova; fertilisation in the fallopian tube is followed by implantation, pregnancy and birth.

Gametogenesis

Spermatogenesis in seminiferous tubules starts at puberty; one primary spermatocyte gives 4 sperms.
Oogenesis starts before birth; one primary oocyte gives 1 ovum and polar bodies.
Menstrual cycle (~28 days): menstrual, follicular, ovulatory (LH surge ~day 14), luteal phases.

Fertilisation to birth

Fertilisation happens in the ampulla of the fallopian tube; zygote → morula → blastocyst.
Blastocyst implants in the endometrium; placenta forms and secretes hCG, hPL, oestrogen, progesterone.
Human pregnancy lasts about 9 months; oxytocin triggers labour; colostrum gives early antibodies.

Key terms

Ovulation: release of the secondary oocyte from the Graafian follicle
Implantation: attachment of the blastocyst to the uterine wall
Corpus luteum: structure formed after ovulation that secretes progesterone

Important questions with answers

What is the role of Sertoli cells?2 marks

Sertoli cells in the seminiferous tubules nourish developing germ cells during spermatogenesis.

Describe the phases of the menstrual cycle with hormonal control.3 marks

Menstrual phase (days 1–5): the endometrium breaks down when progesterone falls. Follicular phase (days 5–13): FSH and LH grow the follicle; oestrogen rebuilds the endometrium. Ovulation (about day 14): an LH surge releases the ovum. Luteal phase (days 15–28): the corpus luteum secretes progesterone to maintain the endometrium; if there is no fertilisation, it degenerates and menstruation begins again.

Describe spermatogenesis and oogenesis and give four differences between them.5 marks

Spermatogenesis: spermatogonia (2n) in seminiferous tubules divide by mitosis, become primary spermatocytes, undergo meiosis I to form secondary spermatocytes and meiosis II to form spermatids (n), which turn into sperms (spermiogenesis). Oogenesis: oogonia form before birth; primary oocytes stay arrested in prophase I until puberty; at each cycle one completes meiosis I forming a secondary oocyte and a polar body; meiosis II completes only after sperm entry, giving the ovum and another polar body. Differences: (1) place – testis vs ovary; (2) one spermatocyte gives 4 sperms, one oocyte gives 1 ovum; (3) spermatogenesis is continuous from puberty, oogenesis starts before birth and is cyclic; (4) sperms are small and motile, ova large and non-motile.

Quick revision

LH surge causes ovulation.
Fertilisation site: ampulla.
Progesterone maintains the endometrium.

Exam tips

Spermatogenesis: 1 → 4 sperms; oogenesis: 1 → 1 ovum.
Remember hormone roles in the menstrual cycle: FSH grows follicles, oestrogen thickens the endometrium, LH surge causes ovulation, progesterone maintains it.

Practice MCQs

Sperms are produced in the
1. epididymis
2. prostate
3. vas deferens
4. seminiferous tubules
Show answer
Answer: (d) seminiferous tubules. Seminiferous tubules.
Fertilisation in humans usually occurs in the
1. uterus
2. ovary
3. cervix
4. fallopian tube (ampulla)
Show answer
Answer: (d) fallopian tube (ampulla). Ampulla.
Ovulation is triggered by a surge of
1. FSH
2. LH
3. oxytocin
4. prolactin
Show answer
Answer: (b) LH. LH surge.
The corpus luteum mainly secretes
1. progesterone
2. oestrogen
3. hCG
4. testosterone
Show answer
Answer: (a) progesterone. Maintains endometrium.
The hormone detected in pregnancy test kits is
1. FSH
2. oxytocin
3. LH
4. hCG
Show answer
Answer: (d) hCG. Made by the placenta.
One primary spermatocyte forms how many sperms
1. 1
2. 2
3. 4
4. 8
Show answer
Answer: (c) 4. Two meiotic divisions.
The embryo stage that implants in the uterus is the
1. zygote
2. blastocyst
3. morula
4. gastrula
Show answer
Answer: (b) blastocyst. Blastocyst.
The number of eggs released from one primary oocyte after both meiotic divisions is
1. 4
2. 2
3. 3
4. 1
Show answer
Answer: (d) 1. Others become polar bodies.

All chapters of Class 12 Biology

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.