During a trip to the Galapagos Islands, which observation led Charles Darwin to suspect that organisms change over time? Island finches were able to breed with mainland species. Island finches resembled mainland finches, but were not the same species. Island finches resembled extinct species from other islands around the world. Island finches did not have beaks of the same size and shape.

Island finches did not have beaks of the same size and shape

Explanation:

This is the evidence of variation, and therefore proof that the finches were able to survive the selective pressure by adapting their beaks to different feeds. Therefore finches that were able to adapt adjusted their beak shapes to the selecting pressure 'feeds' in the environment, and are naturally selected, and therefore adapted and evolved with time. While those without the surviving beaks lost out.

Thus changes in selection pressure, necessitated corresponding change in the beaks shape for adaption to survive (due to variation,) and therefore natural selection for evolution