Final answer:
Darwin's finches in the Galapagos underwent adaptive radiation, where a single ancestor diversified into multiple species with unique beak shapes designed for specific diets, exemplifying allopatric speciation and the process of natural selection.
Step-by-step explanation:
The finches that Charles Darwin observed in the Galapagos are a classic example of adaptive radiation, which is an evolutionary process where organisms diversify rapidly from an ancestral species into a multitude of new forms. The different beak shapes of Darwin's finches are among the most vivid examples of this process. These beaks evolved to best adapt to the finches' varying diets, which includes seeds, insects, and nectar. The original finch species likely dispersed from the mainland and adapted rapidly to the novel ecological niches available on the islands through genetic mutations, giving rise to different species.
Coming from a likely common ancestor, these finches settled on islands where their particular traits—such as beak size and shape—were most advantageous, leading to reproductive isolation and subsequent speciation. The divergent beak morphologies enabled each finch species to exploit different food resources and reduce competition amongst them. As a result, a single species gave rise to many, with each new species adapted to a specific way of life.
This also illustrates an example of allopatric speciation, where different populations evolve independently due to physical separation, forming distinct species with unique traits that fit their habitat's demands.