Which of the following must exist in a population before natural selection can act upon that population? A) genetic variation among individualsB) variation among individuals caused by environmental factorsC) sexual reproductionD) Three of the responses are correct. E) Two of the responses are correct.

A) genetic variation among individuals

Explanation:

Natural selection is the process of better survival fitness of certain individuals of a population than the other. This is due to the presence of some genetic traits that make these organisms better adapted to the prevailing conditions. These genetic traits are not present in other individuals of the population. Therefore, the presence of genetic variations in the natural populations is required for natural selection to favor the better-adapted individuals.

For example, a bacterial population should have some bacteria with antibiotic resistance genes to allow natural selection to operate on this population.