Answer to Question #74789 in Evolution for Alexandra David
The figure below depicts the relationship between fitness and phenotype (“character”), and how this relationship changes from Time 1 to Time 3 as the environment changes. “X” represents that average value of the character in a population. Selection is acting on this population in Time 1, moving the value of X towards maximum fitness. a) assuming at this point that selection is the only force acting on the population, explain why X gets “stuck” towards the left of the graph (a low value of the character) even as, by Time 3, a high value for the character confers the highest fitness . b) if other forces could act on this population, which one(s) could drive the population mean for the character to the right (to the global optimum)?