What conclusion(s) can be made if one knows that allele frequencies stay the same from one generation to the next?

Question

A. Evolution has occurred.

B. Natural selection has occurred.

C. The modern synthesis has occurred.

D. All of the above.

E. None of the above.

Answer 1

The question assumes Hardy-Weinberg equilibrium. There are some strict rules that we need to follow when we are in Hardy-Weinberg equilibrium; that is,mutations are not present, there is random mating, gene flow is absent, infinite population, and no natural selection. Evolution does not occur. Evolution is the change in allele frequency over time. Now, we can exclude A,B,and D! C is tricky, because this is a Darwin/Mendelian concept that factors in evolution. Given that evolution is no longer occurring, we can exclude that from our answer choices. Answer choice E appears to be the correct answer!

Answer 2

A. In terms of alleles, evolution can be thought of as the change in allele frequencies in a given population over time. If the frequencies have not changed, then evolution has not occurred

B. This answer could be true if there is selection for heterogeneous alleles. For example, if you have a population with 50/50 white and red eyes, and the next generation also has 50/50 white and red eyes, natural selection may favor offspring who have both alleles, (and conversely, having homogeneous alleles AA or aa, has a lower fitness than Aa) which drives it towards that 50/50 split. This is the basis for Hardy-Weinberg equilibrium. However, if allele frequencies don't change, that can also be a sign of no natural selection happening, since natural selection can also drive allele frequencies towards fixation, so I'm hesitant to say this is the correct answer, even though it may be technically true.

C. Modern synthesis is the fusion of Mendelian genetics with Darwinian evolution, and it basically describes what I said in part A, that evolution can be thought of as the change in allele frequencies.

I would put E on an exam but I would argue that B is the correct answer. Sorry if it sounds confusing, let me know if you need any help.

Best of luck.