The figure below depicts the relationship between fitness and phenotype (“charac
ID: 211938 • Letter: T
Question
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)? Explain your response.
(a)Time 1 b) Time 2 () Time 3 Global optimum Character Character CharacterExplanation / Answer
a) In case of Time 1, the low value of character has greater fitness than the high value. The most probable cause of this kind of feature might be the environmental factors which have corresponding influence on the phenotype of the individual. Sometimes environmental factors like color of the surrounding habitat favors a particular phenotype more than other variances of the phenotypes. This correspondence of a particular phenotype to the surrounding environment leads to natural selection of a particular phenotype of a species.
b) Other forces that can act on this population are like genetic drift due to factors like geographic isolation. These natural forces lead to some drastic mutations. Among them, one or two of the mutations give rise to such phenotypic characters which are highly favored by natural selection and give rise to global optimum.
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