Which of the following must exist in a population before natural selection can act upon that population? A. genetic variation among individuals B. variation among individuals caused by environmental factors C. sexual reproduction (random fertilization) D. A and C only E. A, B and C

Answer is Option "A"

Explanation:

Genetic variation is the variation in alleles and genes, both within and among populations. Think of a population as a family unit. Within your family of closely-related individuals there is genetic variation. Within a neighbourhood, there are many families, and so there is also genetic variation among that larger groupGenetic variation can be identified through either continuous or discrete traits. Continuous traits are traits that vary continuously, such as height and weight. Discrete traits are traits that can only be measured discretely, such as tongue rolling; you either can or can't do thisThere are three sources of genetic variation: mutation, gene flow, and sexual reproduction.A mutation is simply a change in the DNA. Mutations themselves are not very common and are usually harmful to a population.Because of this, mutations are usually selected against through evolutionary processesHence, the right answer is option A "genetic variation among individuals"