In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
-
The cells in the 12 cell lines grown in low-glucose conditions showed the effects of which of the following processes?
A) gene flow and genetic drift
B) natural selection and mutation
C) natural selection and gene flow
D) conjugation and transformation

Question

In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population. 
-
The cells in the 12 cell lines grown in low-glucose conditions showed the effects of which of the following processes?
A) gene flow and genetic drift 
B) natural selection and mutation 
C) natural selection and gene flow 
D) conjugation and transformation

Quizplus · Accepted Answer

The experiment involves selecting for E. coli cells that are able to survive and reproduce in low-glucose conditions. This selection pressure leads to the evolution of adaptations, which are the result of mutations that confer higher fitness in the new environment. Therefore, the cells in the 12 cell lines grown in low-glucose conditions show the effect of both natural selection and mutation. There is no evidence of gene flow, genetic drift, conjugation, or transformation in this experiment.

In This Eight-Year Experiment, 12 Populations of E