A scientist studying a large population of a particular species of bird concludes that monarch butterflies are toxic to that bird species.
However, upon studying a second, smaller population of the same bird
species, he discovers that the second population is able to eat monarchs
without becoming sick. How could the scientist best explain his findings?
A. The larger bird population has a small gene pool.
B. Monarchs are only toxic if eaten in large quantities.
C. Genetic drift has occurred in the smaller population.
D. Natural selection has increased populations of non-toxic butterflies.