The following questions refer to Figure 27.1.
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.

Figure 27.1
-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) sexual selection
E) stabilizing selection

Question

The following questions refer to Figure 27.1.
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.
  
Figure 27.1
-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) sexual selection 
E) stabilizing selection

Quizplus · Accepted Answer

The experiment shows microevolution, as the populations of E. coli evolved over 20,000 generations in response to low-glucose conditions. However, there is no evidence in the experiment that speciation, adaptive radiation, sexual selection, or stabilizing selection occurred.

The Following Questions Refer to Figure 27.1