Final answer:
Darwin's finches demonstrate adaptation through variations in beak shape, suited to different food sources on the Galápagos Islands, exemplifying the principle of adaptive radiation.
Step-by-step explanation:
Darwin's finches exhibit a classic example of adaptation in response to different environmental pressures on the Galápagos Islands. The variation in beak shape among finch species illustrates adaptive radiation, a process by which organisms diversify rapidly into many new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches. For instance, some finches have evolved large, robust beaks suitable for cracking open hard seeds, whereas others have developed long, slender beaks, perfect for extracting nectar from flowers or small insects from tight spaces. These adaptations are supported by decades of research, notably by Peter and Rosemary Grant, who provided empirical evidence that even within a few generations, natural selection can lead to changes in beak sizes as the birds adapt to the available food sources, as seen in the medium ground finch.
For example, after a period of heavy rain due to an El Niño event, where there was an abundance of small, soft seeds and a dearth of large, hard seeds, the finches with smaller beaks had better survival and reproductive success. Over time, this resulted in a decrease in average beak size within the population. Therefore, demonstrating that beak shape is an inherited trait that evolved over time, allowing finches to exploit different types of food resources on the islands.