Question

Why was the reduction of the bison population to under 1,000 individuals a bottleneck event for the species?
a.
It drastically reduced the gene pool of the species.
b.
It reduced the territorial range available to the species.
c.
Foreign genes were introduced by crossbreeding with cattle.
d.
It reduced the prevalence of recessive traits.

Answer 1

a. It drastically reduced the gene pool of the species.

Explanation: A population bottleneck sharply reduces population size and thus genetic diversity (the gene pool). That loss of alleles increases inbreeding and can magnify harmful recessive traits; the other options are not the primary definition of a genetic bottleneck.