1. The Origin of Species 24.2

2. Speciation can take place with or without geographic separation 24.2

3. Recall: Speciation  The formation of a new species  Reproductive isolation is key

4. 2 Modes of Speciation  (a) Allopatric  (b) Sympatric

5. Allopatric Speciation  “Other country”  Geographically isolated populations  Separated gene pools diverge as mutations, natural selection events occur within each population  Eventual reproductive isolation  Example: fruit flies and food medium

6. Sympatric Speciation  “Same country”  Speciation occurs within populations  Some kind of reproductive barrier isolates members of the population  Examples: polyploidy, habitat differentiation, sexual selection

7. Polyploidy  Extra sets of chromosomes in cells  More common in plants

8. Habitat Differentiation  Genetic factors enable a subpopulation to utilize a habitat/resources the parent species cannot  Example: apple maggot flies  Parent species a pest of hawthorn fruit  Subspecies began laying eggs in apples which mature faster  Temporal isolation developed  Hawthorn flies develop more slowly than apple maggot flies

9. Sexual Selection  Females select mates based on appearance  Example: cichlids