Reproduction

Definition: The process by which organisms produce new individuals of their own kind.

Types:

• Asexual Reproduction: Does not involve fusion of gametes. Offspring are genetically identical to parent (Clones).
• Sexual Reproduction: Involves fusion of male and female gametes (fertilization). Offspring have genetic variations.

1. Binary Fission: Division of parent body into two equal halves (e.g., Bacteria, Amoeba).

2. Multiple Fission: Division of parent nucleus into many daughter nuclei, each surrounded by cytoplasm (e.g., Amoeba in unfavorable conditions).

3. Fragmentation: Body breaks into pieces, each piece develops into new organism (e.g., Planaria).

4. Budding: A small outgrowth (bud) forms on parent body, grows, and detaches (e.g., Yeast, Hydra). In Corals, buds do not detach (forming colonies).

5. Spore Formation: Production of thick-walled spores in Sporangia (e.g., Rhizopus/Fungi). Bacteria form Endospores for survival.

6. Parthenogenesis: Development of egg into new organism without fertilization (e.g., Honey bees: Drones are haploid).

Natural Methods:

• Bulbs: Underground stem with fleshy leaves (Onion, Tulip).
• Corms: Underground stem (Garlic).
• Rhizomes: Horizontal underground stem (Ginger, Ferns).
• Tubers: Swollen underground stem tip with 'eyes' (Potato).
• Runners (Stolons): Horizontal stem on ground surface (Strawberry).
• Suckers: Stem arising from root (Mint).
• Leaves: Adventitious buds on leaf margins (Bryophyllum).

Artificial Methods:

• Cuttings: Stem/root cuttings (Rose).
• Grafting: Joining parts of two plants (Stock and Scion).

Alternation of Generations: Life cycle involves two generations:

• Sporophyte (2n): Dominant, produces haploid spores by Meiosis.
• Gametophyte (1n): Produces haploid gametes by Mitosis.

Flower Structure:

• Calyx (Sepals): Protection.
• Corolla (Petals): Attraction.
• Androecium (Male): Stamens. Anther produces pollen grains (Male Gametophyte).
• Gynoecium (Female): Carpels. Ovary contains ovules (develop into seeds). Egg is formed in Embryo Sac (Female Gametophyte).

1. Pollination: Transfer of pollen from anther to stigma. (Self vs Cross Pollination).
   • Insect Pollinated: Colorful, nectar, sticky pollen.
   • Wind Pollinated: Dull, no nectar, lightweight pollen.
2. Fertilization: Pollen tube grows to ovary. Double Fertilization is unique to Angiosperms:
   • Sperm + Egg -> Zygote (2n).
   • Sperm + Fusion Nucleus -> Endosperm Nucleus (3n).
3. Seed Formation: Ovule -> Seed. Ovary -> Fruit.

Structure: Embryo (Radicle, Plumule, Cotyledons), Testa (Seed Coat), Endosperm (Food).

Types:

• Epigeal: Cotyledons come above ground (e.g., Bean, Cotton).
• Hypogeal: Cotyledons remain underground (e.g., Pea, Maize).

Conditions: Water, Oxygen, Optimum Temperature.

Gametogenesis: Formation of gametes.

• Spermatogenesis: Production of sperms in Testes (Seminiferous tubules). Diploid Spermatogonia -> Primary Spermatocytes -> Meiosis -> Haploid Spermatids -> Sperms.
• Oogenesis: Production of eggs in Ovaries (Follicles). Diploid Oogonia -> Primary Oocytes -> Meiosis -> Haploid Egg (Ovum) and Pola Bodies.

• External Fertilization: Gametes fuse outside female body. Requires water. Many gametes lost (e.g., Fish, Amphibians).
• Internal Fertilization: Gametes fuse inside female body. Developing embryo protected (e.g., Reptiles, Birds, Mammals).

Male Reproductive System: Testes (in Scrotum), Epididymis, Vas Deferens, Urethra, Glands (Seminal Vesicles, Prostate, Cowper's).

Female Reproductive System: Ovaries, Oviducts (Fallopian tubes), Uterus (Horns, Cervix), Vagina (Birth Canal).

Fertilization: Occurs in Oviducts. Zygote develops in Uterus.

Overpopulation: When population exceeds capacity of resources. Causes shortage of water, jobs, education, health facilities.

Control: Pakistan started addressing overpopulation in 1960. Govt and NGOs educating people.

Census: Collection of data about inhabitants. Pakistan Bureau of Statistics conducts census.

Cause: HIV (Human Immuno-deficiency Virus). Attacks white blood cells (destroying immune system).

Transmission: Sexual contact, contaminated needles, blood transfusion.

Control in Pakistan: National AIDS Control Programme (NACP) established 1987. NGOs (AAS, Nai Zindagi) also working for awareness and support.