Regarding the Drosophila melanogaster experiment from your textbook: Low populat

Question

Regarding the Drosophila melanogaster experiment from your textbook: Low population density 6High population density R1 R2 R3 K1 K2 K3 Drosophila melanogaster lineages Figure 51.13 Evolution of foraging behavior by laboratory populations of Drosophila melanogaster. After 74 generations of living at low population density, D. melanogaster larvae (popula- tions R1-R3) followed foraging paths significantly shorter than those of D. melanogaster larvae that had lived at high density (populations K1-K3) Imagine a hypothetical follow-up experiment in which, after 74 generations, 1/2 the R1-R3 population is put into a small enclosure, giving them a high density environment. In this new high-density R1-R3 population, what would you expect to see with regard to the allele frequencies between the 74th and 75th generations? O Allele frequency would not be affected. Foraging behavior is based on each individual choosing to do whichever behavior is appropriate for their environment. O The larvae would be unfit for their environment and die, so the allele frequency question is not applicable. O The ForS allele would increase in frequency O The ForR allele is fixed, therefore there could be no change. O The ForR allele would increase in frequency O The larvae have no choice in their behavior, so the allele frequencies would stay the same.

Explanation / Answer

The ForR allele would increase in frequency.

As observed in the experiment over many generations, ForR allele frequency increased in larvae living in high population density, and Forse allele frequency increased under low population density. Although it is just one generation (from 74th to 75th), still a small increase in ForR allele is expected because larvae with ForR allele will be able to travel longer distance and hence more suitable for high density population, giving them fitness advantage over larvae with ForS allele.

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