Answer: Dr. Kettlewell concluded that the observed shift in moth coloration was the result of natural selection, with the darker moths being better adapted to survive in heavily polluted environments.
Explanation: Dr. Kettlewell's experiments on bird predation of the moths were conducted in the 1950s and 1960s and focused on the peppered moth, a species that occurs in both light and dark forms. The study found that birds were more likely to prey on the lighter, more visible moths when they rested on trees covered in soot and industrial pollution, while the darker moths were better able to camouflage and avoid predation. Dr. Kettlewell concluded that the observed shift in moth coloration was the result of natural selection, with the darker moths being better adapted to survive in heavily polluted environments.