Final answer:
Darwin's finches on the Galapagos Islands intrigued Darwin due to their adaptation through modified beaks for survival in diverse environments.
Explanation:
Darwin's finches, as observed by Charles Darwin on the Galapagos Islands, were particularly interesting to him because the birds were related but had been modified to survive under different conditions. He noted a graded series of beak sizes and shapes among the finches, indicating they descended from one original mainland species and adapted to various habitats by developing different beak types for specific food sources.
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