The following question refers to the figure.
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.

Which term best describes what has occurred among the experimental populations of cells over this eight-year period?
A) microevolution
B) speciation
C) adaptive radiation
D) stabilizing selection

Question

The following question refers to the figure.
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.

Which term best describes what has occurred among the experimental populations of cells over this eight-year period?
A) microevolution 
B) speciation 
C) adaptive radiation 
D) stabilizing selection

Quizplus · Accepted Answer

The experiment involved 12 populations of E. coli that were grown in low-glucose conditions for 20,000 generations. This prolonged exposure to a particular environmental condition led to microevolutionary changes, as evidenced by the differences in fitness levels between the ancestral and experimental populations. Additionally, the fact that the populations did not diverge enough to form new species or experience adaptive radiation suggests that the changes were relatively small-scale and occurred within the same lineage or species.

The Following Question Refers to the Figure