speciation Flashcards
how can one species form in to 2 species?
reproductive isolation. when part of a population stops breeding with another group in the same population…over time 2 populations could form and if they stop interbreeding it could lead to a new species.
what are 3 types of reproductive isolation?
- behavioral isolation, 2. geographic isolation, 3. temporal isolation
behavioral isolation occurs when….?
when 2 groups within a population split up due to different courtship rituals and stop interbreeding. Ex. eastern and western larks.
geographic isolation occurs when….?
2 groups oft he same species are separated by a physical barrier (such as a river or mountain) and stop breeding. Ex. finches of the GALAPAGOS.
temporal isolation occurs when…?
when 2 or more species reproduce at different times. Ex. orchids that bloom and pollinate on different days.
Describe how the finches in the Galapagos evolved by founders effect?
The birds were perhaps brought to the island by a storm and due to isolation the allele frequencies would have differed from their original population making the way for a new species to form.
Describe how the finches evolved by geographic isolation?
When the birds crossed over to even more islands, the gene pools would not be shared by birds on each island (since birds very rarely crossed islands), leading to the potential of another species to form via natural selection.
Describe how the finches evolved from changes in gene pool
directional selection would have favored birds with bigger beaks for bigger seeds on one island and small beaked birds for smaller seeds on another island…Therefore, natural selection would favor specific phenotypes (beak size). Hence, genotype allele frequency for each population of birds on each island would become different.
Describe how the finches evolve via behavioral isolation?
If the finches from one island return back to their original island, they do not breed with the finches there because their mating techniques are different.
