What trait variation did Charles observe after studying the Galapagos finches?

He noticed that each finch had a different type of beak in order to obtain whatever food it ate.

Explanation:

a physical change is being made.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.