We are given two rules about genetic mutation and natural selection.
(1) If one of the effects of a genetic mutation makes a substantial contribution to the survival of the species, then, and only then, will that mutation be favored in natural selection.
(2) If the traits that were not favored were still carried along by a trait that was favored, then the unfavored trait must not be so negative that it annuls the benefits of having the new, favored trait.
Answer choice (E) states: "A genetic mutation whose effects are all neutral to a species is favored in natural selection."
Well, we know according to rule #1 that a genetic mutation will be favored in natural selection if one of the effects of a genetic mutation makes a substantial contribution to the survival of the species. So, if it does not makes a substantial contribution, then it is not favored in natural selection.
Thus, we cannot have a genetic mutation whose effects are ALL neutral (i.e. none of them makes a substantial contribution to the survival of the species) be favored in natural selection.
So, since this is a "could be true EXCEPT" question, answer choice (E) is our answer.
Hope that was helpful! Please let us know if you have any other questions.
mikeheathMay 12, 2020
Couldn't E be true if it's neutral effects are relative to other genetic mutations whose traits are all negative?
