Natural selection can only occur if there is variation among members of the same species. ... Variation in a population results from mutation and the recombination of alleles during meiosis and fertilization.

What happens to natural selection if there is no variation?

Without genetic variation, a population cannot evolve in response to changing environmental variables and, as a result, may face an increased risk of extinction. For example, if a population is exposed to a new disease, selection will act on genes for resistance to the disease if they exist in the population.

Is variation necessary for natural selection?

Natural selection requires variation in a population of organisms. For the process to work, at least some of that variation must be heritable and passed on to organisms' descendants in some way.