Biology 3.5

Biology 3.5

1. Natural Selection

   • Selection
     • Disruptive
     • Stabilising
     • Directional
   • Fossils = evidence
   • Structures
     • Homologous
       • Same origin, different fuction
       • Forelimb bones
     • Analogous
       • Different origin, similar function
         • Wings

2. Speciation

   • Steps
     • 1. Geographic barrier
     • 2. Selection pressures
       • Diverging
     • 3. Mutations and isolating mechanisms
   • Allopatric
     • Different origins
     • Different areas
       • Prevents gene flow
   • Sympatric
     • Same origin
     • Different behaviours
       • Not common in animals
   • Instantaneous
     • Polyploidy
       • Uncommon in animals
         • Common in plants
       • Extreme climates
       • 3n, 4n etc.
       • Auto
       • Allo

3. Groups

   • Cline
     • Gradual Change
   • Ring
     • "Loop" over geographic area
       • Interbreeding
         • Except for two ends
       • Deme

4. Patterns of Evolution

   • Convergent
     • Different ancestors
     • Similar selection pressures
   • Divergent
     • Common ancestor
       • Splits due to niches
     • Isolated from main gene pool
   • Adaptive radiation
     • Ancestral species
       • Evolves into diverse species
       • Climate change
   • Parallel
     • Similar features
     • Common ancestor
   • Co-evolution
     • Close ecological relationship

5. Evolutionary Change

   • Gradualism
     • Slowly
     • Continuously
   • Punctuated Equilibrium
     • Long periods of no change
       • Stasis
     • Rapid speciation
       • Sudden changes in environment
   • Founder Effect
     • Colonisising
       • Limits gene pool
   • Bottleneck
     • Reduction in population
       • Limits gene pool

6. Reproductive Isolating Mechanisms

   • Pre-zygotic
     • Geography
     • Temporal
     • Ecological
     • Structural
     • Ethological
   • Post-zygotic
     • Sterility
     • Breakdown
     • Inviability