Draw a graph of relative fitness and number of mutations of an evolving strain versus the ancestral strain over 20,000 generations under the same growth conditions
Explain the change in fitness and mutations over time using evolutionary concepts and terms.
What will be an ideal response?
Answer: The graph should show an initial rapid increase in fitness during the first few 1,000 generations followed by a slower increase in fitness thereafter. Mutations should increase at a steady rate over the entire 20,000 generations (as shown in Figure 12.22). Fitness increases rapidly at first because random mutations lead to fitness increases early on when the strain is introduced into a new environment/growth condition. However after the first few random beneficial changes, increases in fitness are slower and more incremental. The mutation rate over the entire 20,000 generations is constant. The initial increase in fitness is not because of an increased mutation rate.
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