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Download The Origin of Species
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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” 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 Sympatric Speciation “Same country” Speciation occurs within populations Some kind of reproductive barrier isolates members of the population Examples: polyploidy, habitat differentiation, sexual selection Polyploidy Extra sets of chromosomes in cells More common in plants 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 Sexual Selection Females select mates based on appearance Example: cichlids
