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.

Compare the bacteria in the figure above in generation 1 and generation 20,000. The bacteria in generation 1 have a greater ________.
A) efficiency at exporting glucose from the cell to the environment
B) ability to survive on simple sugars, other than glucose
C) ability to synthesize glucose from amino acid precursors
D) reliance on glycolytic enzymes

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.

Compare the bacteria in the figure above in generation 1 and generation 20,000. The bacteria in generation 1 have a greater ________.
A) efficiency at exporting glucose from the cell to the environment 
B) ability to survive on simple sugars, other than glucose 
C) ability to synthesize glucose from amino acid precursors 
D) reliance on glycolytic enzymes

Quizplus · Accepted Answer

The bacteria in generation 1 have a greater reliance on glycolytic enzymes because they are adapted to high-glucose conditions. Over the course of the experiment, the populations evolved to have a reduced reliance on glycolytic enzymes since they were grown in low-glucose conditions. This adaptation can be seen in the figure where the fitness of the evolved populations (red lines) is significantly higher than that of the ancestral population (blue line) at low-glucose concentrations.

The Following Question Refers to the Figure