Class 10 Ch 7 How do Organisms Reproduce?

• Reproduction is NOT essential for individual survival but is VITAL for species continuity.
• DNA Copying: Chromosomes in the nucleus contain DNA (Information source).
• No biochemical process is 100% accurate $\to$ Variations (विभिन्नता) are created.
• Why Variation? It allows species to survive environmental changes (e.g., heat-resistant bacteria).

Single parent produces offspring. No gametes involved.

• Fission (खंडन): Unicellular organisms divide.
  – Binary: Amoeba (any plane), Leishmania (fixed plane).
  – Multiple: Plasmodium (Malarial parasite).
• Fragmentation: Spirogyra breaks into smaller pieces.
• Regeneration (पुनरुद्भवन): If cut, pieces grow into new individuals (Ex: Planaria, Hydra).

• A small bud develops as an outgrowth due to repeated cell division.
• Ex: Hydra, Yeast.

New plants produced from root, stem, or leaves.

• Natural:
  – Root: Sweet potato.
  – Stem: Potato, Ginger.
  – Leaf: Bryophyllum (buds produced in leaf notches).
• Artificial: Layering (Jasmine), Grafting (Rose/Mango).
• Advantage: Plants like Banana, Orange, Jasmine that have lost the capacity to produce seeds can be grown. Genetic similarity is maintained.
• Tissue Culture: Growing plants from cells in an artificial medium. Sterile & Disease-free.

• Bread mould (Rhizopus) has thread-like hyphae with blobs called Sporangia.
• Spores are thick-walled for protection against harsh environments.

• Involves two parents. DNA recombination leads to variations.
• Gametes (Germ cells) carry half the number of chromosomes.

पुष्प के भाग: बाह्यदल, पंखुड़ी, पुंकेसर एवं स्त्रीकेसर।

• Stamen (Male): Anther (pollen) + Filament.
• Carpel/Pistil (Female): Stigma (top), Style (tube), Ovary (bottom).
• Pollination: Transfer of pollen from anther to stigma. (Self vs Cross).
• Fertilization: Pollen tube grows through style to reach ovary. Zygote forms $\to$ Embryo $\to$ Seed.

• Humans use Internal Fertilization.
• Puberty (यौवनारंभ): Period when reproductive tissues begin to mature.
• Common Changes: Hair growth (armpits/pubic area), oily skin/pimples.
• Girls: Breast size increases, start of Menstruation.
• Boys: Thick facial hair, voice cracks.

• Testes: Produce sperms & Testosterone. Located in Scrotum (outside body) for lower temperature required for sperm production.
• Vas Deferens: Tube carrying sperms.
• Prostate & Seminal Vesicles: Add fluids to make transport easy and provide nutrition.

• Ovaries: Produce eggs (ova) & Estrogen/Progesterone.
• Oviduct (Fallopian Tube): Site of Fertilization.
• Uterus (Garbhashaya): Where embryo develops.
• Placenta: Special tissue for nutrition & waste exchange between mother and foetus.

• Uterus lining thickens every month to receive zygote.
• If fertilization doesn’t occur, the lining breaks and comes out through the vagina as blood and mucus.
• This is Menstruation (lasts 2-8 days).

Important to avoid STDs and unwanted pregnancies.

• STDs (Sexually Transmitted Diseases):
  – Bacterial: Gonorrhoea, Syphilis.
  – Viral: Warts, HIV-AIDS.