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.

The process is called ultrafiltration. The filtration pressure allows fluid to be pushed out of the connecting capillaries (the major portion of the glomerulus) and into the Bowman's capsule leading to the rest of the kidney nephron.