Which of the following is a requirement for natural selection to operate?

Natural selection relies on the presence of variation in traits among individuals within a population. This variation is crucial because it allows some individuals to possess advantageous traits that enhance their chances of survival and reproduction in a given environment. When individuals with these favorable traits reproduce, they pass those traits on to the next generation, gradually leading to evolution within the population.

If all individuals had the same reproductive success, there would be no differential survival or reproduction based on traits, which is essential for natural selection to occur. Additionally, while the inheritance of traits is important for evolution, not all traits must necessarily be inherited for natural selection to operate. Environmental changes can also influence natural selection; in fact, changing environments can drive the need for certain traits to provide a survival advantage. Thus, variation among individuals is the fundamental requirement for natural selection to take place.