Final answer:
The diversification of species from a common ancestor through adaptation to different ecological niches on the Galapagos Islands is known as adaptive radiation. The Galapagos finches are a classic example, where different beak shapes evolved to exploit different food resources, resulting in multiple new species originating from a single ancestral species.
Step-by-step explanation:
Darwin hypothesized that the different species of finches he observed on the Galapagos Islands had all descended from a single ancestor species of finch on the mainland. This diversification into many species all adapted to different ecological niches is known as adaptive radiation. Adaptive radiation is the process by which a single species evolves into many new species to fill available niches in the environment.
In the case of Galapagos finches, this phenomenon is particularly striking because the finches display a variety of beak shapes and sizes each specialized for different types of food sources. This indicates that after the finches settled on the islands from the mainland, they adapted to the new ecologies of the individual islands. Natural selection favored those beak shapes that were most efficient at utilizing the food resources available, resulting in the proliferation of new finch species from one common ancestor.