can anyone answer a darwin question??

[dessy2591]

why did darwin believe that the finches he obsereved and collected in the Galapagos Islands shared a common ancestor??

[sachin]

He thought that,

Finches of Galapagos might have got isolated geographically from there ancestors, due to geographical barrier Sea...

[Dustfinger]

Yes, and they had similar looks but different beaks.

[Darby]

First, they were all finches.

Second, the "base" finch, the Galapagos ones still living like the South American mainland finches, were assumed to be remnants of the original founding group, with the others adapted starting from that basic finch ancestor. That's how Darwin was formulating his theories. Finch species differed from the "base" with traits that made sense if splinter groups had adapted to niches that were available on the Galapagos (but would have been occupied on the mainland).

Third, the Galapagos are 1000 kilometers from the source of their original founding (terrestrial) species in Ecuador, so it was easy to believe that founding populations are each only gotten there once. That might not have been right, but it made sense.

Fourth, it was a great example supporting the theories Darwin eventually presented to the world, so he was inclined to see them that way.

[satrohraj]

He collected 20 different species of Finches which differ mainly in Shape, Size of the beak and color of the plumage (Feathers) from the species he collected from South America.

He explained it in this way;

South American Finches (ancestors of finches in Galapagos Island) migrated to different islands in Galapagos, and adapted themselves to respective environments and different food habits like cactus feeding, warbler-like, woodpecker-like, etc. And they evolved into different species

He called this adaptation to different habitats and new ways of life as "adaptive radiation".

[satrohraj]

Actually he collected the observed the finches in South Equador (S.America)
He collected and observed the species from Galapagos island which is 970 miles from coast of South Equador