Question

Your response to the question should be long enough to address the question but limited to no more than two pages. These are essay style questions therefore you should give essay style answers. Do not copy the published work of others. If you cite the work of someone else, please provide the appropriate citation.

Observations that Charles Darwin made during his five year voyage around the world on the H.M.S. Beagle and especially during his visit to the Galápagos Islands provided him with important clues towards developing a theory of evolution. What insights did Darwin obtain from his study of finches on the Galápagos Islands and natural history studies during his travels and why were these important pieces to the puzzle solving the “species problem” and in developing his theory of evolution?

Answer 1

Charles Darwin proposed theory of evolution during his five year voyage around the world on the H.M.S. Beagle and his observations on finches in Galapagos islands provided him with insights in the changes taking place in organisms favored by the selection. His experiences and observations were recorded and proposed the theory of evolution in his book, "The origin of species". Basing on observations on finches in Galapagos Islands, Darwin proposed that the finches with different shapes of beaks have descended from a common ancestor. Peter and Rosemary grant have identified that the Darwin’s hypothesis was based on two testable assumptions.

One is the order for beak size and shape to evolve enough inheritable variation must occur in the traits provides a raw material for natural selection. The other one is differences in beak size and shape produces difference in fitness allowing the natural selection to occur. The grants have tested this hypothesis on medium ground pinch on Daphne Major one the Galapagos Islands.

To prove the natural selection as the mechanism of the evolution proposed by Darwin, Peter and Rosemary grant of Princeton University had studied on the banding and measuring of finches on Galapagos Islands.

Grants first task was the identification and measurement of several individual birds on a single island. They observed and recorded the details of birds living and died and birds succeeded in breeding and which had not. The wing length, leg length, beak length, beak depth, beak color, feather color and total mass of the bird were also recorded. These characters have appeared in bell shaped distributions of polygenic traits. From this data Grants gave a conclusion that great variation of inheritable traits was observed in Galapagos finches.

Grants observed that the individual birds with varying beak sizes have different chances of survival during draught. When the food sources are scarce the birds with the largest beaks were able to survive and the beak size plays an important role in the mating behavior resulting in average beak size in the population. The change in the beak size is based on the directional selection. These observations clearly evident in support of theory of evolution.