Reproductive Isolating Mechanisms

• Reproductive isolating mechanism

  Any factor that prevents two organisms from different species from mating and producing fertile offspring.
• How does reproductive isolation occur

  Populations are isolated so gene flow is restricted, leading to speciation (formation of a new species)
• Type of RIM: Geographical Isolation


  When physical barriers like mountains, rivers, or distances prevent species from meeting and mating. This is Allopatric speciation.
• Type of RIM: Temporal Isolation


  When species breed at different times of the day, season, or year. This is Sympatric speciation
• Type of RIM: Ecological isolation


  When species occupy different habitats within the same area, causing them to rarely encounter each other. This is Sympatric speciation.
• Type of RIM: Behavioural isolation


  Happens from differences in mating behaviours or rituals that prevent species from recognising each other as potential mates. This is Sympatric speciation.
• Type of RIM: Mechanical Isolation

  when differences in genital structures or incompatible reproductive organs prevents successful mating between species. This is Sympatric speciation.
• Pre-zygotic isolating mechanisms

  Occur before fertilisation and prevent the formation of a zygote.
• Types of Pre-zygotic isolating mechanisms

  • Temporal isolation
  • Ecological isolation
  • Mechanical Isolation
  • Behavioural isolation
  • Gametic Isolation (incompatible gametes)
• Post-zygotic isolating mechanisms

  Occur after fertilisation and affect the viability or fertility of the hybrid offspring.
• Types of Post-zygotic isolating mechanisms

  • Hybrid inviability ( hybrid offspring don't develop properly)
  • Hybrid Sterility (hybrid offspring are sterile)
  • Hybrid break down( hybrid offspring are fertile but their descendants are sterile)
• Pre Zygotic and Post Zygotic Isolating Mechanisms

  Both maintain species boundaries and prevent gene flow between distinct species.