The beaks of finches found on various Galápagos Islands differed based on?

the food that they ate

Explanation:

The beaks of finches found on various Galápagos Islands differed based on the food that they ate. The finches that survived on eating different larger nuts had strong beaks for breaking the nuts open. While the Finches that ate smaller type nuts and seeds had beaks for cracking nuts and seeds. This also applied to other types of animals as well, each adapting to its own necessities.