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The Origin of Species

The Origin of Species. 24.2. Speciation can take place with or without geographic separation. 24.2. Recall: Speciation. The formation of a new species Reproductive isolation is key. 2 Modes of Speciation. (a) Allopatric (b) Sympatric. Allopatric Speciation. “Other country”

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The Origin of Species

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  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

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