CHP.-1.REPRODUCION IN ORGANISMS

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CHP.-1.REPRODUCION IN ORGANISMS

• CLASS- XII

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• Life span The period from birth to natural
  death of an organism.
• Reproduction a biological process in which an
  organism gives rise to young ones similar to
  itself.
• Types of reproduction
• Asexual reproduction offspring is produced by a
  single parent with or without formation of
  gametes.
• Sexual reproduction When two parents
  participate in reproductive process also
  involve fusion of male female gametes.

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Asexual reproduction

• Budding in Yeast

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Binary fission - Amoeba
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Zoospores of Chlamydomonas
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Conidia of Penicillium
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Buds in Hydra
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Gemmules in sponge
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Vegetative propagation in plants (Eyes of potato)
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Rhizome of ginger
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Bulbil of Agave
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Leaf buds of Bryophyllum
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Offset of Water hyacinth
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Sexual reproduction

• Events in sexual reproduction
  1.Pre-fertilisation events
• (i) Gametogenesis
• (ii) Gamete transfer
• 2. Fertilisation
• 3.Post-fertilisation events
• (i) Zygote (ii) Embryogenesis

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Pre-fertilisation events

• 1.Gametogenesis
• It is the process of formation of male female
  gametes.
• Homogametes morphologically similar.
• Heterogametes morphologically different.

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• Bisexual male female reproductive structures
  in the same plant.(Homothallic Monoecious ).
• Unisexual male female reproductive structures
  on different plants. (Heterothllic Dioecious).
• Gametes are haploid.
• In diploid organisms specialised cells called
  meiocytes ( gamete mother cell ) undergo meiosis.

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• 2.Gamete transfer
• In most of the organisms male gamete is motile
  the female gamete is stationary.
• In aquatic plants gamete transfer takes place
  through Water.
• Male gametes are produced in very large number
  because a large number of male gametes are lost
  during transport.

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• 3. Fertilisation
• Fusion of gametes is known as syngamy which
  results in the formation of Zygote.
• External fertilisation syngamy occurs outside
  the body of the organism. Eg. Algae, Fishes,
  Amphibians.
• Internal fertilisation syngamy occurs inside
  the body of organism. Eg. Reptiles, Birds,
  Mammals, most of the plants.

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Post-fertilisation events

• 1. The Zygote
• 2. Embryogenesis
• It is the process of development of embryo from
  the Zygote.
• Zygote undergo cell division
• (Mitosis) cell differentiation.
• Oviparous animals lay eggs Eg. Reptiles,
  birds.
• Viviparous animals- zygote develop into a young
  one inside the body of female organism.