American bison were hunted almost to extinction in the late 1800s. The rapid decrease in (species / population / group) size of the bison has reduced the

genetic (equilibrium / evolution / diversity) of the animals. This kind of

(genetic drift / polygenetic shift / environmental effect) likely occurred

because only a few individuals survived from the original larger population. A

change in (habitat conditions / allele frequencies / genetic equilibrium)

following a large reduction in population size is called a(n) (bottleneck effect /

polygenetic effect / environmental effect).

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