What is required for natural selection to occur?

Natural selection requires genetic variation within a population because this diversity provides the raw material for evolution. In a population where individuals exhibit varied traits, some traits may confer advantages that improve survival and reproduction under specific environmental conditions. For example, if a particular trait helps individuals better access food or evade predators, those individuals are more likely to survive and reproduce, passing that advantageous trait to the next generation. This process gradually shifts the population toward more favorable traits, illustrating how evolution occurs through natural selection.

In contrast, homogeneous populations lack genetic variation, meaning all individuals are genetically similar and face the same survival challenges. Without variation, there are no different traits for selection to act upon. High levels of inbreeding further reduce genetic diversity and can lead to increased vulnerability to diseases or environmental changes, while static environmental conditions do not create the pressures necessary for different traits to be favored or selected against, stifling the process of natural selection.