Q. Why is variation beneficial to the species but not necessarily for the individual?
A variation may be beneficial to the species but not necessarily for the individual. This can be understood with the following hypothetical example. Let us recall how giraffe may have evolved from their ancestors who had shorter necks. A giraffe had had to crane its neck longer to reach the uppermost branches. For most of the individual giraffe, it must have been a painful experience. But in the long run, those who could succeed in reaching the uppermost branches survived and others perished. So, developing a longer neck had no foreseeable short term gains but it was beneficial for the species.