Scientists study the possible effects of human activity on the genetic variations within members of two populations of sparrows, A and B, that live within similar ecosystems. Population A lives in a recreational campsite while population B lives in a nature preserve. Both populations exhibit similar genetic variation between the parent population and second generation. However, a tornado touches down in the habitat of population A during the lifespan of the second generation.

Which statement best describes the predicted difference between the third generation of the two populations?

A) Population B underwent a speciation that will lead to an increase in the genetic variation of the third generation compared to population A due to natural selection.
B) Population A underwent a speciation that will lead to an increase in the genetic variation of the third generation compared to population B due to natural selection.
C) Population B underwent a bottleneck effect that will lead to a decrease in the genetic variation of the third generation compared to population A due to genetic drift.
D) Population A underwent a bottleneck effect that will lead to a decrease in the genetic variation of the third generation compared to population B due to genetic drift.