Reproduction = production of new individuals. Essential for species continuation, not individual survival. AMU asks 3–4 MCQs — focus on asexual reproduction types, flower structure & double fertilization, human reproductive system, menstrual cycle, and contraception.
1) Asexual vs Sexual reproduction
| Feature | Asexual | Sexual |
|---|---|---|
| Parents | One | Two (male + female) |
| Gametes | Not formed | Male & female fuse (fertilization) |
| Offspring | Genetically identical (clones) — no variation | Genetically different — variation (due to recombination) |
| Cell division | Mitosis only | Meiosis (gamete formation) + Mitosis |
| Speed | Rapid | Slow |
| Evolutionary advantage | Well-adapted clones in stable environment | Variation helps adaptation in changing environment |
2) Asexual reproduction — types
| Type | Process | Examples |
|---|---|---|
| Binary fission | Parent divides into two equal daughters | Amoeba (irregular), Paramecium (transverse), Euglena (longitudinal), Bacteria, Leishmania (longitudinal) |
| Multiple fission | Nucleus divides many times → many daughters released together | Plasmodium (malaria parasite); Amoeba forms cyst → multiple fission in unfavourable conditions |
| Budding | Outgrowth (bud) forms on parent → grows → detaches | Hydra, Yeast |
| Fragmentation | Parent body breaks into fragments → each grows into new individual | Spirogyra (algae), Planaria (flatworm), Starfish |
| Regeneration | Ability to regrow lost body parts; some can regenerate whole body from fragment | Planaria (from 1/279th fragment!), Hydra, Lizard tail, Starfish arm |
| Spore formation | Spores (with thick protective wall) produced in sporangium → germinate in favourable conditions | Rhizopus (bread mould), Penicillium, Mushrooms, Ferns |
Fig: Budding in Hydra — stages from bud formation to detachment
2.1 Vegetative propagation (plants)
| Natural method | Example | Description |
|---|---|---|
| Tuber | Potato | Eyes (axillary buds) grow into new plants |
| Bulb | Onion, Garlic | Fleshy leaves store food; new bulbs form as offsets |
| Runner | Strawberry, Grass | Horizontal stem runs along ground → nodes root & shoot |
| Sucker | Banana, Pineapple | Underground stem grows upward as new shoot |
| Rhizome | Ginger, Turmeric | Thick underground stem; nodes produce roots & shoots |
| Leaf | Bryophyllum | Adventitious buds on leaf margin → plantlets → new plants |
| Modified root | Sweet potato, Dahlia | Adventitious buds on roots grow into new plants |
Artificial methods: Cutting (sugarcane, rose), Layering (jasmine), Grafting (mango, apple — scion + stock), Tissue culture (orchids, banana — micropropagation in sterile medium).
Advantages: Quick, identical clones preserve desirable traits, sterile plants can reproduce.
Advantages: Quick, identical clones preserve desirable traits, sterile plants can reproduce.
🔥 AMU PYQ: Bryophyllum reproduces through:
(A) Leaves (B) Stems (C) Roots (D) Spores Ans: A
(A) Leaves (B) Stems (C) Roots (D) Spores Ans: A
3) Sexual reproduction in flowering plants
3.1 Flower structure
• Calyx (sepals) → protects bud. Corolla (petals) → attracts pollinators.
• Androecium (stamen: filament + anther) → produces pollen grains (male gametophyte).
• Gynoecium (pistil: stigma + style + ovary) → ovary contains ovules (female gametophyte).
• Androecium (stamen: filament + anther) → produces pollen grains (male gametophyte).
• Gynoecium (pistil: stigma + style + ovary) → ovary contains ovules (female gametophyte).
3.2 Pollination
| Type | Agent | Flower features | Examples |
|---|---|---|---|
| Self (Autogamy) | Same flower/plant | — | Pea, Wheat, Rice |
| Cross (Allogamy) | Different plant (variation) | — | Most plants |
| Wind (Anemophily) | Wind | Small, no scent, feathery stigma, light pollen | Maize, Grass, Wheat |
| Insect (Entomophily) | Insects (bees, butterflies) | Bright, scented, nectar, sticky pollen | Sunflower, Rose, Jasmine |
| Water (Hydrophily) | Water | Underwater/ floating flowers | Vallisneria, Hydrilla |
3.3 Double fertilization (unique to angiosperms)
Pollen grain → Germinates on stigma → Pollen tube grows through style to ovule → 2 male gametes released.
• 1st male gamete + Egg cell → Zygote (2n) → Embryo
• 2nd male gamete + 2 Polar nuclei → Triploid (3n) endosperm → food for embryo
Discovered by S. G. Nawaschin (1898).
• 1st male gamete + Egg cell → Zygote (2n) → Embryo
• 2nd male gamete + 2 Polar nuclei → Triploid (3n) endosperm → food for embryo
Discovered by S. G. Nawaschin (1898).
• Fertilized ovule → Seed. Ovary → Fruit.
• Parthenocarpy: Fruit without fertilization → seedless fruits (banana, grapes).
• Seed dispersal: Wind (dandelion), Water (coconut), Animals (Xanthium hooks, berries), Explosive (castor).
• Parthenocarpy: Fruit without fertilization → seedless fruits (banana, grapes).
• Seed dispersal: Wind (dandelion), Water (coconut), Animals (Xanthium hooks, berries), Explosive (castor).
🔥 AMU PYQ: Double fertilization occurs in:
(A) Gymnosperms (B) Angiosperms (C) Pteridophytes (D) Bryophytes Ans: B
(A) Gymnosperms (B) Angiosperms (C) Pteridophytes (D) Bryophytes Ans: B
🔥 AMU PYQ: Endosperm in angiosperms is:
(A) Diploid (B) Haploid (C) Triploid (D) Tetraploid Ans: C
(A) Diploid (B) Haploid (C) Triploid (D) Tetraploid Ans: C
4) Human reproductive system
4.1 Male
Testes (in scrotum, 2–3°C cooler → sperm production) → Epididymis (sperm storage & maturation) → Vas deferens → joins Seminal vesicles (fructose-rich fluid, 60% semen) + Prostate (alkaline fluid, 30% semen) + Cowper's glands (lubrication) → Urethra (common passage for urine & semen) → Penis.
• Testes produce sperm (spermatogenesis) and testosterone.
• Testes produce sperm (spermatogenesis) and testosterone.
4.2 Female
Ovaries (produce ova + estrogen/progesterone) → Fallopian tubes (site of fertilization = ampulla) → Uterus (implantation, foetal development) → Cervix → Vagina.
• At birth: ~1–2 million primary oocytes; only ~300–400 mature in lifetime.
• At birth: ~1–2 million primary oocytes; only ~300–400 mature in lifetime.
4.3 Menstrual cycle (~28 days)
| Phase | Days | Events | Hormones |
|---|---|---|---|
| Menstrual | 1–5 | Endometrium sheds → bleeding | Low estrogen & progesterone |
| Follicular | 6–13 | FSH → follicle grows → secretes estrogen → endometrium thickens | FSH ↑, Estrogen ↑ |
| Ovulation | 14 | LH surge → ovum released from Graafian follicle | LH surge |
| Luteal | 15–28 | Corpus luteum secretes progesterone → maintains endometrium; degenerates if no pregnancy | Progesterone ↑ |
🔥 AMU PYQ: Ovulation occurs around day:
(A) 1 (B) 7 (C) 14 (D) 28 Ans: C
(A) 1 (B) 7 (C) 14 (D) 28 Ans: C
4.4 Fertilization to birth
• Fertilization in ampulla of fallopian tube → Zygote → Morula → Blastocyst → Implantation (day 6–7 in endometrium).
• Placenta connects foetus to mother — exchange of O₂, CO₂, nutrients, wastes; produces hCG, progesterone, estrogen.
• Pregnancy: ~40 weeks (9 months).
• Parturition: Oxytocin stimulates uterine contractions → baby delivered.
• Placenta connects foetus to mother — exchange of O₂, CO₂, nutrients, wastes; produces hCG, progesterone, estrogen.
• Pregnancy: ~40 weeks (9 months).
• Parturition: Oxytocin stimulates uterine contractions → baby delivered.
4.5 Contraception
| Method | Examples | Mechanism |
|---|---|---|
| Barrier | Condoms, Diaphragm, Spermicides | Prevents sperm reaching ovum; condoms prevent STDs |
| Hormonal | OCPs (pills), Injectables, Implants, Patches | Inhibit ovulation (no LH surge); contain estrogen + progesterone |
| IUD | Cu-T (Copper-T), Mirena | Copper ions spermicidal; prevents implantation |
| Surgical | Vasectomy (male — vas deferens cut); Tubectomy (female — fallopian tubes cut) | Permanent sterilisation |
| Natural | Rhythm method (safe period), Withdrawal | Avoid fertile days; less reliable |
| Emergency | Morning-after pill (i-Pill) | Within 72 hrs; prevents/delays ovulation |
🔥 AMU PYQ: Permanent contraception in males is:
(A) Condom (B) Vasectomy (C) IUD (D) Tubectomy Ans: B
(A) Condom (B) Vasectomy (C) IUD (D) Tubectomy Ans: B
5) Variation in sexual reproduction
Sources: Crossing over (prophase I of meiosis — exchange of genetic material), Independent assortment (different chromosome combinations in gametes), Random fertilization (any sperm × any ovum).
• Variation is crucial for evolution — enables populations to adapt.
• Variation is crucial for evolution — enables populations to adapt.
6) AMU PYQs — quick revision
Q1. Amoeba reproduces by:
(A) Budding (B) Binary fission (C) Fragmentation (D) Spore formation Ans: B
(A) Budding (B) Binary fission (C) Fragmentation (D) Spore formation Ans: B
Q2. Pollen grains are produced in:
(A) Ovary (B) Anther (C) Stigma (D) Style Ans: B
(A) Ovary (B) Anther (C) Stigma (D) Style Ans: B
Q3. Site of fertilization in human female is:
(A) Ovary (B) Uterus (C) Fallopian tube (D) Vagina Ans: C
(A) Ovary (B) Uterus (C) Fallopian tube (D) Vagina Ans: C
Q4. Implantation occurs in:
(A) Ovary (B) Fallopian tube (C) Uterus (D) Cervix Ans: C
(A) Ovary (B) Fallopian tube (C) Uterus (D) Cervix Ans: C
Q5. The function of placenta is:
(A) Gamete production (B) Exchange of nutrients & wastes (C) Milk production (D) Fertilization Ans: B
(A) Gamete production (B) Exchange of nutrients & wastes (C) Milk production (D) Fertilization Ans: B
Q6. Which part becomes fruit?
(A) Ovary (B) Ovule (C) Sepal (D) Petal Ans: A
(A) Ovary (B) Ovule (C) Sepal (D) Petal Ans: A
Q7. Vegetative propagation through leaves occurs in:
(A) Potato (B) Ginger (C) Bryophyllum (D) Onion Ans: C
(A) Potato (B) Ginger (C) Bryophyllum (D) Onion Ans: C
Q8. Number of chromosomes in human sperm:
(A) 46 (B) 23 (C) 44 (D) 22 Ans: B
(A) 46 (B) 23 (C) 44 (D) 22 Ans: B
Q9. Which STD is caused by a virus?
(A) Gonorrhoea (B) Syphilis (C) Genital herpes (D) Chlamydia Ans: C
(A) Gonorrhoea (B) Syphilis (C) Genital herpes (D) Chlamydia Ans: C
Q10. Pollination by wind is called:
(A) Hydrophily (B) Anemophily (C) Entomophily (D) Ornithophily Ans: B
(A) Hydrophily (B) Anemophily (C) Entomophily (D) Ornithophily Ans: B
Q11. LH surge triggers:
(A) Menstruation (B) Ovulation (C) Implantation (D) Fertilization Ans: B
(A) Menstruation (B) Ovulation (C) Implantation (D) Fertilization Ans: B
Q12. Which is NOT asexual reproduction?
(A) Budding (B) Binary fission (C) Syngamy (D) Fragmentation Ans: C (Syngamy = gamete fusion = sexual)
(A) Budding (B) Binary fission (C) Syngamy (D) Fragmentation Ans: C (Syngamy = gamete fusion = sexual)
Q13. The main advantage of sexual over asexual is:
(A) Faster (B) Genetic variation (C) Identical offspring (D) No mate needed Ans: B
(A) Faster (B) Genetic variation (C) Identical offspring (D) No mate needed Ans: B
📝 Pro Tip for AMU: Binary fission (Amoeba = irregular; Paramecium = transverse; Euglena = longitudinal). Hydra = budding; Planaria = regeneration + fragmentation. Flower: anther produces pollen, ovary becomes fruit. Double fertilization: 1 male + egg = zygote (2n); 2nd male + polar nuclei = endosperm (3n). Human: fertilization in fallopian tube, implantation in uterus. Vasectomy = male, Tubectomy = female sterilization. Ovulation = day 14 (LH surge).