Which component is necessary for natural selection to occur?

Genetic variation within a population is essential for natural selection to occur because it provides the raw material for evolution. This variation arises from mutations, genetic recombination during reproduction, and other processes, creating differences among individuals in traits such as size, color, and resistance to disease.

For natural selection to act, these variations must affect the organisms' ability to survive and reproduce in their environment. If all individuals were genetically identical, they would respond similarly to environmental pressures, and there would be no differences for selection to favor one trait over another. Thus, genetic variation ensures that some individuals may be better suited to their environment, leading to differential survival and reproduction, which is the essence of natural selection.

Stability in environmental conditions is not a requirement for natural selection; in fact, changing conditions often drive the process. Uniform reproduction rates can inhibit diversity necessary for evolution, and limitless resources are seldom found in nature, further demonstrating that genetic variation is crucial for survival and evolution.