How are finches in the Galapagos is lands a good example of adaptation?

Answer 1

These birds, although nearly identical in all other ways to mainland finches, had different beaks. Their beaks had adapted to the type of food they ate in order to fill different niches on the Galapagos Islands. Their isolation on the islands over long periods of time made them undergo speciation (form new species).
Darwin wrote about his travels in the book The Voyage of the Beagle and fully explored the information he gained from the Galapagos Finches in his most famous book On the Origin of Species.
It was in that publication that he first discussed how species changed over time.