Darwin’s Finches An example of Adaptive Radiation

The Galapagos Islands

Finch Types: Using Darwin’s Theory, explain how all of these different species evolved.

“Seeing this gradation & diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.” Darwin…one smart guy…

Phylogenetic Trees Show evolutionary “relatedness” Based on fossil record, dna evidence, structural similarity, etc

What common ancestor do all of These organisms share?

Darwin’s Finches…again… What common ancestor do the seed eating and cactus eating finches share ? What do each of the finch pictures on here represent? Which 2 species are more closely related: a.Mangrove Finch and Woodpecker finch b.Small ground finch and Bud-eating finch

Good Questions with Good Answers. How can new species be formed and the old one not go extinct? Wasn’t the whole reason a new species formed was that it had a survival advantage?

Speciation does NOT necessarily cause EXTINCTION! A NEW SPECIES’ existence just means… That POPULATION’S GENE POOL has been altered so much that there are new genes in EVERY MEMBER’S GENOTYPE And THESE NEW GENES make it impossible for them to mate with members of the other population NOW there are TWO SPECIES Eventually…one may go extinct, but NOT NECESSARY!!!

Geographic Isolation… Sometimes populations are spit In two due to a geographic barrier. This can lead to reproductive isolation. How could this lead to speciation?

Reduction of Gene Flow… If members of a species live far away from each other, they will have a decreased chance of mating. This would create reduced gene flow, but not total isolation. Speciation would probably also require different selective pressures at the two ends. Eventually, this could alter gene frequencies in groups at different ends of the range so much that they would not be able to mate if they were reunited…that’s speciation!