🌱 Biology — Reproduction in Plants and Animals
1. Asexual Reproduction
MODES OF ASEXUAL REPRODUCTION
- Fission: Equal division of cell (e.g., Amoeba)
- Fragmentation: Breaking of body part → whole organism (e.g., Spirogyra, Bryophytes)
- Regeneration: Any part forms new part (e.g., Hydra)
- Budding: Bud grows into new organism (e.g., Hydra, Yeast)
- Vegetative propagation: Vegetative parts (root, stem, leaf) develop new plants (e.g., Sugarcane, Rose)
- Spore formation: Spores germinate into new organisms (e.g., Algae, Fungi)
ARTIFICIAL VEGETATIVE PROPAGATION
- Grafting, Cutting, Layering, Micropropagation (Tissue culture)
- Can be practiced throughout the year
- Produces clones (genetically identical plants)
2. Sexual Reproduction in Plants
FLOWER STRUCTURE
- Androecium: Male reproductive part (stamens)
- Gynoecium: Female reproductive part (carpels)
- Bisexual flower: Both male and female parts
- Unisexual flower: Only male or female part
POLLINATION
- Anemophily: Pollination by wind
- Hydrophily: Pollination by water
- Entomophily: Pollination by insects
- Ornithophily: Pollination by birds
- Chiropterophily: Pollination by bats
- Malacophily: Pollination by snails
- Myrmecophily: Pollination by ants
FERTILISATION & POST-FERTILISATION CHANGES
| Before Fertilisation | After Fertilisation |
|---|---|
| Ovary | Fruit |
| Ovule | Seed |
| Outer integument | Testa (tough seed coat) |
| Inner integument | Tegmen (delicate) |
| Endosperm nucleus | Endosperm |
| Egg cell | Embryo |
3. Sexual Reproduction in Humans
MALE REPRODUCTIVE SYSTEM
- Testis: Produces sperms (spermatogenesis) and testosterone
- Epididymis: Site of sperm maturation and storage
- Vas deferens: Transports sperm
- Prostate gland: Secretes alkaline fluid to neutralise vaginal acidity
- Seminal vesicle: Secretes fructose-rich fluid
- Sperm pathway: Seminal vesicle → Rete testis → Vasa efferentia → Epididymis → Urethra
FEMALE REPRODUCTIVE SYSTEM
- Ovaries: Produce eggs (oogenesis) and hormones (estrogen, progesterone)
- Fallopian tubes (Oviducts): Site of fertilisation
- Uterus: Site of implantation and foetal development
- Vagina: Birth canal; receives penis during coitus
- Menstrual cycle: ~28 days in humans
- Ovum pathway: Ovary → Fallopian tube → Uterus
SECONDARY SEXUAL CHARACTERS
| Character | Man | Woman |
|---|---|---|
| General build | More muscular | Less muscular |
| Facial hair | Beard & moustache | Absent |
| Mammary glands | Undeveloped | Well developed |
| Voice | Low pitched | High pitched |
4. Reproductive Health
CONTRACEPTIVE METHODS
- Barrier methods: Condoms, Diaphragms, Cervical caps, Contraceptive sponges
- IUD (Intra Uterine Device): Small plastic device with copper/hormones; prevents implantation
- Oral contraceptives: Birth control pills (estrogen + progesterone)
- Abstinence: 100% effective in preventing pregnancy and STDs
- Withdrawal: Removal of penis before ejaculation
- Surgical methods: Tubectomy (female), Vasectomy (male)
ASSISTED REPRODUCTIVE TECHNOLOGIES (ART)
- IVF (In Vitro Fertilisation): Egg fertilised outside body; embryo transferred to uterus
- ICSI (Intra Cytoplasmic Sperm Injection): Single sperm injected into mature egg
- GIFT (Gamete Intra Fallopian Transfer): Egg transferred to fallopian tube
- ZIFT (Zygote Intra Fallopian Transfer): Zygote transferred to fallopian tube
- Three-parent babies: Uses DNA from three people; maternal spindle transfer
- Mitochondrial Replacement Therapy: Replaces faulty mitochondrial DNA with healthy donor mitochondria
SEXUALLY TRANSMITTED DISEASES (STDs)
- Bacterial STDs: Chlamydia, Gonorrhoea, Syphilis
- Viral STDs: HIV/AIDS, Hepatitis-B, Genital herpes, HPV
- Protozoan STD: Trichomoniasis
- Parasitic STDs: Scabies, Crabs
- Amniocentesis: Prenatal diagnosis of chromosomal abnormalities; misused for sex determination
Summary: Reproduction at a Glance
| Topic | Key Point |
|---|---|
| Asexual Reproduction | Fission, Budding, Fragmentation, Vegetative propagation |
| Pollination by Insects | Entomophily |
| Pollination by Birds | Ornithophily |
| Sperm Production | Testis (spermatogenesis) |
| Egg Production | Ovary (oogenesis) |
| Fertilisation Site | Fallopian tube (Oviduct) |
| Universal Donor (Blood) | Blood group O |
| Universal Recipient | Blood group AB |
KEY TAKEAWAYS FOR UPSC
- Asexual reproduction: Fission (Amoeba), Budding (Hydra, Yeast), Vegetative propagation (Sugarcane)
- Pollination types: Anemophily (wind), Entomophily (insects), Ornithophily (birds)
- Sperm pathway: Testis → Epididymis → Vas deferens → Urethra
- Ovum pathway: Ovary → Fallopian tube → Uterus
- Fertilisation: Occurs in fallopian tube
- Menstrual cycle: ~28 days
- Contraceptives: Barrier, IUD, Oral pills, Surgical (Vasectomy, Tubectomy)
- ART: IVF, ICSI, GIFT, ZIFT
- STDs: HIV/AIDS, Hepatitis-B, Syphilis, Gonorrhoea
- Amniocentesis: Prenatal diagnosis; misused for sex determination
High-Yield Interactive UPSC Quiz (Biology — Reproduction)
Q1. Which type of reproduction occurs in Amoeba?
Correct Answer: B. Amoeba reproduces by binary fission (asexual reproduction).
Q2. Pollination by insects is called:
Correct Answer: B. Entomophily is pollination by insects.
Q3. What is the site of fertilisation in humans?
Correct Answer: B. Fertilisation occurs in the fallopian tube (oviduct).
Q4. Where does spermatogenesis occur?
Correct Answer: B. Spermatogenesis occurs in the testis.
Q5. The menstrual cycle in humans is approximately:
Correct Answer: C. The menstrual cycle in humans is approximately 28 days.
Q6. Which method is 100% effective in preventing pregnancy and STDs?
Correct Answer: C. Abstinence is the only contraceptive method that is 100% effective in preventing both pregnancy and STDs.
Q7. What is the surgical method of male sterilisation called?
Correct Answer: B. Vasectomy is the surgical method of male sterilisation.
Q8. Which STD is caused by a virus?
Correct Answer: C. HIV/AIDS is a viral STD.
Q9. What does IVF stand for?
Correct Answer: B. IVF stands for In Vitro Fertilisation.
Q10. Pollination by bats is called:
Correct Answer: C. Chiropterophily is pollination by bats.