Some genes or allelles become more common over time because of beneficial effects that they have on survival and reproduction. A species' particular habitat, the ecological opportunities they exploit. Includes diet, where they live, when they are active. Two species are not expected to share the same exact niche for long. Active during the night.
Insectivores usually hunt insects at night facilitated by big eyes.
The product of the interaction between genotype and the environment. E.g., your body. Almost all primate societies are female philopatric. Females stay with their natal group, males migrate. Species arranged on a family tree.