Question

In the case of directional selection, if the advantageous allele (b) is recessive and a less advantageous allele (B) is dominant:

A. b will be lost in the population because the dominant allele will increase in frequency by natural selection

B. b will increase in frequency at the same speed as if it was a dominant advantageous allele, because what matters is the coefficient of selection and not if the allele is dominant or recessive

C. b will increase in frequency but if it has a low initial frequency it will take a longer time than if it were a dominant allele

D. natural selection will make b dominant E. both alleles will be maintained indefinitely in the population

E. both alleles will be maintained indefinitely in the population

Michael Wade set up an experiment in which he propagated Tribolium castaneum beetles under three different treatments. In the control treatment (C), he propagated all populations into each subsequent generation. In treatment B, he propagated only groups with the smallest population sizes. In a third treatment (A), he propagated only groups with the largest population size . After 9 generations, all three evolved populations became more likely to cannibalize pupae, and females laid fewer eggs than the ancestral population. What conclusions did Dr. Wade reach about natural selection, and why?

A.     He said he had demonstrated that selection might operate on the level of phenotypes without genetic variation (also called epigenetic selection). Treatment B was a form of group selection that reinforced this epigenetic selection. Treatment A was a form of group selection that opposed the consequences of epigenetic selection.

B.     He said he had demonstrated that selection might operate at two levels: among individuals and among genes. Treatment B was a form of gene selection that reinforced the individual level selection. Treatment A was a form of gene selection that opposed consequences of individual selection.

C.      He said he had demonstrated that selection might operate at two levels: among individuals and among populations. Treatment B was a form of group selection that reinforced the individual level selection. Treatment A was a form of group selection that opposed consequences of individual selection.

D.     He said he had demonstrated that selection only operates at the individual level. Although in treatment B he selected the smallest groups, the results were the same as the individual selection treatment. Further, although in treatment A he selected the largest groups, the results were also the same as the individual selection treatment.

E.      He said that he had proved that Darwin’s theory of natural selection was false, and that species must therefore have originated by intelligent design.

When the poison warfarin was used to control rats in Wales, the frequency of resistant rats increased rapidly; it then declined rapidly when the poisoning program was ended. What is the most likely explanation of the decline in resistance?

A. a decrease in the rate at which mutations for resistance arise.

B.   genetic drift of the susceptible genotype.

C.   a fitness cost of the resistance adaptation.

D.   coalescence to a susceptibility gene, due to stochastic loss of gene lineages.

E.   due to lack of exposure to warfarin, individuals did not develop resistance    antibodies.

What is the main difference between natural selection and genetic drift?

A. only natural selection changes allele frequency

B. within a specific environment, changes due to selection are consistent and predictable, while changes due to drift are not

C. only genetic drift maintains variation within populations

D. only drift affects the history of descent of gene copies

E. unlike drift, selection is important only in small population

Answer 1

1. C. b will increase in frequency but if it has a low initial frequency it will take a longer time than if it were a dominant allele

because in directional selection the adventageous alleles will increase in population irrespective of dominant or recessive

2.C.      He said he had demonstrated that selection might operate at two levels: among individuals and among populations. Treatment B was a form of group selection that reinforced the individual level selection. Treatment A was a form of group selection that opposed consequences of individual selection.

3. D.   coalescence to a susceptibility gene, due to stochastic loss of gene lineages.

4. B. within a specific environment, changes due to selection are consistent and predictable, while changes due to drift are not