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
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• 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.
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• 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