Reproduction in Organisms

Sexual Reproduction- pre-fertilisation, fertilisation, post fertilisation

Sexual reproduction :

  • It is  also referred as Amphimixis, Syngenesis (or) Amphigony
  • Characteristics
    → Biparental
    → No rapid multiplication
    → Mitosis/ Meiosis
    → Daughter organisms graphically differ from parents
  • On the basis of fusing gametes source syngamy is of 2 types (i) Endogamy (self Fertilization) Eg. Taenia and (ii) exogamy (cross fertilization)
  • On the basis of structure of fusing gametes syngamy is of 4 types
  • There events in sexual reproduction is pre fertilization, fertilization and post fertilization.
  • Gametogenesis and Gameti transfer are the two steps in pre-fertilization
  • Types of meiosis
    ⇒ Zygotic meiosis Eg. Chlamydomonas
    ⇒ Sporic meiosis Eg- Plants
    ⇒ Gametic meiosis Eg. Animals
  • Two types of Fertilization are (i) External (Eg. Bony fishes /Amphibians) most algae - (ii) Internal fertilization - Reptile, Birds, mammals
  • Post fertilization involves Zygote development and Embryogenesis.
  • Parthenogenesis
  • Development of an egg into a complete individual without fertilization.
  • Advantage
    ⇒ Rapid mode of division
    ⇒ Simple and easier means of reproduction
    ⇒ Sex determination in honey bees
  • No role in Evolution as is provides no variation.
  • Egg has all the factors, essential for development, but only it needs stimulus for the development

Part-1: Watch this video for the topic from 36:49 to 51:16

Part-2: Watch this video for the topic from 0:40 to 51:50

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