A scientist is studying the genetics of a population of plants that she suspects is undergoing natural selection. After examining samples of the population’s DNA over several years, she finds the following data:
|Year||Allele A Frequency||Allele B Frequency|
Does this provide evidence of natural selection in this population? Why or why not?
- No, because the genotype frequencies, not allele frequencies, have to change for evolution to occur.
- No, because the allele frequencies are changing randomly, suggesting that genetic drift is occurring, not natural selection.
- Yes, because it shows that the previously favorable or neutral allele A is now being selected against in favor of allele B.
- Yes, because it is showing that the frequency of both alleles are changing over time.
A land manager mows a section of annual grass. Over the years, he recorded the date of flowering from the mown field as well as a similar grass field that was not mown. What is the most likely explanation for this trend?
|Year||Mowed field flowering date||Unmowed field flowering date|
- The grass population is adapting to the mowing, so it can flower for longer before being mowed.
- Mowing stabilizes the flowering time, which follows a steady trend in the mowed field but not in the unmowed field.
- The mowing is preventing the grass from reproducing, causing the mowed field to adapt by flowering earlier.
- The grass typically flowers earlier and earlier every year as it becomes older with each passing year.
A scientist observed two populations of insects for 10 years. They took data on the length, in mm, of the insect’s
mouthparts. Their data is shown in the graphs below. How is this population evolving and what agent of evolution is most
likely at work?
- inbreeding, because the gene distributions are becoming less similar among the population
- genetic drift, as the distribution of traits has become more random
- gene flow, as the population has likely gained new mouthpart traits through immigration
- natural selection, as insects that have mid-sized mouthparts are being favored
Researchers believe that in a fish species, individuals with the recessive genotype aa are predisposed to disease. Homozygous dominant (AA) individuals and heterozygous (Aa) individuals are not believed to be susceptible to this disease. A pond was stocked with 100 fish of the AA genotype and 100 fish of the aa phenotype, and the fish were allowed to breed. In the next generation, 35 percent of the fish had the dominant (AA) phenotype. What does this result indicate?
- The homozygous dominant phenotype is higher than expected, indicating that evolution has occurred.
- The homozygous dominant phenotype is lower than expected, indicating that evolution has occurred.
- The homozygous dominant phenotype is higher than expected, indicating that evolution has not occurred.
- The homozygous dominant phenotype is lower than expected, indicating that evolution has not occurred.
The graph below shows the change in gene frequency of the two alleles of a gene: A and a. The population being
studies has no emigration or immigration. Which type of evolution is likely occurring here and is the allele selected for,
neutral, or selected against by natural selection?
- non-random mating; both alleles are favored
- gene flow; allele A is favored
- genetic drift; both alleles are neutral
- natural selection; allele a is not favored
The graph below shows the change in gene frequency of the two alleles: A and B. These alleles are located on separate genes that do not influence each other in any way. The population being studied has no emigration or immigration. Which type of evolution is likely occurring here, if at all? Explain how you know.
- no multiple choice available
- no multiple choice available
The diagram below shows the frequency of alleles on two species of wind-pollinated plants, as well as the prevailing
wind direction. These frequencies have been fairly stable for around 10 years. However, climate change has created a new
prevailing wind direction, as shown in the diagram. How will the two populations likely evolve in the future?
- natural selection will cause the frequency of B to increase in population 1
- gene flow will cause the frequencies of A and B to drop in population 3
- genetic drift will cause the frequencies of A and C to increase in population 1 and 2
- inbreeding will reduce the frequency of allele B in population 2 and 3