Which best illustrates the relationship between variations within a population and natural selec- tion? a natural selection acts upon a population since all members of the population are identical. b organisms are able to change their genetic makeup to best adapt to a changing external environment. c giraffes have long necks and legs from stretching to reach food in trees. this trait was then passed to their offspring. antelopes with muscular legs are able to outrun their predators better than antelopes with poor muscle tone. thus they lived to reproduce