Final answer:
The large ground finch's short, strong beak is an adaptation resulting from natural selection and adaptive radiation, allowing it to crack hard seeds effectively.
Step-by-step explanation:
The short, strong beak of the large ground finch Geospiza magnirostris is an example of adaptive radiation and natural selection. Through processes described by Charles Darwin, finches on the Galápagos Islands have adapted their beaks over generations to exploit different food sources effectively. For the large ground finch, its beak has evolved to crack open hard seeds, making it thicker and stronger compared to finches that eat other types of food, like insects or nectar.
Observations by researchers such as Peter and Rosemary Grant provide evidence for this evolutionary change. They reported that during a drought, finches with larger beaks could eat more types of seeds, and hence were more likely to survive. Their offspring also tended to have larger beaks, showing evolution by natural selection.