How do Organisms Reproduce?

• Why Do Organisms Reproduce?

  • Creation of DNA copies
  • Ensures species survival and continuity
  • Maintains population stability in ecosystems

• Asexual Reproduction

  • Single parent involvement
  • No gamete formation
  • Genetically identical offspring (Clones)
  • Types of Asexual Reproduction
    • Fission
      • Binary Fission: Division into two equal cells (e.g., Amoeba, Leishmania)
      • Multiple Fission: Division into many cells simultaneously (e.g., Plasmodium)
    • Fragmentation
      • Breaking into pieces, each growing into a new organism (e.g., Spirogyra)
    • Regeneration
      • Regrowing lost/cut body parts (e.g., Planaria, Hydra)
    • Budding
      • Outgrowth detachment forming a new organism (e.g., Hydra, Yeast)
    • Vegetative Propagation
      • New plants from roots, stems, or leaves (e.g., Bryophyllum, potato tubers, layering, grafting)
    • Spore Formation
      • Formation of reproductive spores inside sporangia (e.g., Rhizopus / bread mould)

• Sexual Reproduction

  • Involvement of two parents (Male and Female)
  • Fusion of gametes (Fertilization)
  • Introduces genetic variation (crucial for evolution)
  • Sexual Reproduction in Flowering Plants
    • Parts of a Flower
      • Sepals: Protection in bud stage
      • Petals: Attract pollinators
      • Stamen (Male Reproductive Organ): Anther (produces pollen) and Filament
      • Carpel / Pistil (Female Reproductive Organ): Stigma, Style, and Ovary (contains ovules)
    • Pollination
      • Transfer of pollen grains from anther to stigma
      • Self-Pollination: Same flower or plant
      • Cross-Pollination: Between different plants (via wind, water, insects)
    • Fertilization & Post-Fertilization
      • Pollen tube growth -> Male germ cell fuses with female egg cell
      • Zygote formation -> Embryo
      • Ovary develops into Fruit
      • Ovules develop into Seeds

• Human Reproductive System

  • Male Reproductive System
    • Testes: Produce sperm and hormone testosterone (located in scrotum)
    • Vas Deferens: Transports sperms
    • Urethra: Common passage for urine and sperm
    • Accessory Glands: Seminal vesicles and Prostate gland (provide fluid and nutrition)
  • Female Reproductive System
    • Ovaries: Produce eggs (ova) and hormones (estrogen, progesterone)
    • Fallopian Tubes (Oviduct): Site of fertilization
    • Uterus: Implantation and development of the fetus
    • Vagina: Entry point for sperms and birth canal
  • The Menstrual Cycle
    • Monthly preparation of uterus for pregnancy
    • Breakdown and shedding of uterine lining if fertilization does not occur (Menstruation)

• Reproductive Health

  • STD (Sexually Transmitted Diseases)
    • Bacterial: Gonorrhoea, Syphilis
    • Viral: Warts, HIV-AIDS
  • Contraception Methods (Preventing Pregnancy)
    • Barrier Methods: Condoms, diaphragms (block sperm entry)
    • Chemical Methods: Oral pills (change hormonal balance), spermicides
    • IUDs (Intrauterine Devices): Copper-T, loop (prevent implantation)
    • Surgical Methods: Vasectomy (in males), Tubectomy (in females) - block gamete transport
  • Population Control
    • Managing family size for national health and economic growth
    • Female foeticide/infanticide impacts the sex ratio (need for social awareness)