The Volcano Is Currently Dormant, but in a Hypothetical Future

Multiple Choice

The volcano is currently dormant, but in a hypothetical future scenario, satellite cones at the base of Mt. Kilimanjaro spew sulfurous gases and lava, destroying all life located between the base and 6,000 feet above sea level. As a result of this catastrophe, how should the frequency of the sickle-cell allele change in the remnant human population that survives above 6,000 feet, and which phenomenon accounts for this change in allele frequency?

A) decreases; disruptive selection
B) increases; genetic drift
C) decreases; gene flow
D) increases; nonrandom mating
E) decreases; bottleneck effect