You begin an experiment with two populations of E. coli that are each composed of 100 cells. The cells are all genetically identical (i. e., they are clones). You grow these populations in flasks on a lab bench under identical conditions with sufficient resources for the survival of all individuals. What process will introduce genetic variation into these populations?

Mutation.

Explanation:

Mutation may be defined as the sudden, heritable change in the individual that might affect the genotype and phenotype of the organisms. The mutation can be somatic mutation or germ line mutation.

The two population of bacteria are same but after sometime the mutation might occur in the bacteria that makes their genetic material different. These mutations can make the bacteria strain resistant against the particular chemical and increase their chance of survival in the harsh environment.

Thus, the correct answer is mutation.