GenBio2 | Lesson 3

• Every animal species ensures the survival of its lineage
• Reproduction


  The process by which living organisms produce their offspring
• Types of asexual reproduction

  • Fission (binary)
  • Budding
  • Fragmentation
  • Parthenogenesis
• Fission (binary)


  • Occurs in prokaryotic microorganisms and in some invertebrate, multi-celled organisms
  • Example: Algae & Coral polyps
• Budding


  • Results from the outgrowth part of a cell, leading to a separation from the original organisms into two individuals
  • Example: Hydra
• Fragmentation


  • Breaking of a body into two parts with subsequent regeneration
  • Example: Sea stars
• Parthenogenesis


  • An egg develops into a complete individual without being fertilized
• Types of sexual reproduction

  • Hermaphroditism
  • Separate Sexes
• Hermaphroditism


  • Occurs in animals where both have a male and female reproductive parts
  • They may self-fertilize
  • Self-fertilization is common in animals that have limited mobility or are not motile, such as barnacles and clams
  • Example: Sea slugs or Nudibranchs
• Separate Sexes


  • Determined by the presence of a specific set of chromosomes
  • Environmental sex determination
  • Sex reversal
  • Individuals homozygous for X (XX) are female and heterozygous individuals (XY) for male
  • In birds, ZZ is male and ZW is female
  • Avian sex determination is dependent on the presence of Z and W chromosomes
  • Protogyny "first female" and protandy "first male"
• Types of fertilization

  • External fertilization
  • Internal fertilization
• External fertilization


  • Occurs in aquatic environments where both egg and sperm are released into the water
• Internal fertilization


  • Occur most often in land-based animals, although some aquatic animals also used this method
• Types of development

  • Oviparity
  • Ovoviparity
  • Viviparity
• Oviparity


  • Fertilized eggs are laid outside the female's body and develop there
• Ovoviparity


  • Fertilized egg are retained in the female, but the embryo obtain its nourishment from the egg's yolk
• Viviparity


  • The young develop within the female, receiving nourishment from the mother's blood through a placenta