Speciation

Speciation

1. May Occur:

   • GRADUALLY by the slow accumulation of small changes
   • INSTANTLY by changes in chromosome number through polyploidy
     • POLYPLOIDY

2. Species:

   • ALLOPATRIC
     • (closely) related species that live in DIFFERENT geographic locations
   • SYMPATRIC
     • (closely) related species that live in the SAME geographic location

3. formation of a new species, resulting from population becoming reproductively isolated - gene flow no longer occurs

4. Reproductive Isolating Mechanism

   • factor that stops members of the population of the same species or members of different species from breeding together; acting as a barrier to gene flow
     • Reproductive isolation may result from one or a combination of prezygotic and/or postzygotic isolating mechanisms
   • Postzygotic
     • Hybrid
     • Hybrid Inviability
     • Hybrid sterility
     • Hybrid breakdown
   • Prezygotic
     • Geographical Isolation
       • E.g.
       • Results from physical barriers separating populations
     • Structural (morphological) Isolation
     • Ecological Isolation
     • Temporal Isolation
     • Behavioural Isolation
     • Gametic Isolation

5. Allopatric Speciation

6. Sympatric Speciation