Examine the data (from 1959) displaying the percentage of DDT resistance in insect populations. What statement best explains the trend seen in the data in terms of evolution?

A) The presence of DDT induced mutations in the insect populations. Mosquitoes that needed mutations survived and reproduced with greater success.
B) DDT resistant mosquitoes existed in the population. The presence of DDT selected for mosquitoes that survived the application. Those resistant mosquitoes reproduced with more success.
C) DDT caused phenotypic changes to occur in populations of mosquitoes as the chemical alters the diet of the insects. Mosquitoes with altered diets were able to survive with greater success than non-resistant mosquitoes.
D) DDT resistant mosquitoes were present in the population. Those mosquitoes were able to be tracked with more success than DDT susceptible mosquitoes, which were better camouflaged in the environment and more difficult to collect data on.

B) DDT resistant mosquitoes existed in the population. The presence of DDT selected for mosquitoes that survived the application. Those resistant mosquitoes reproduced with more success.

Explanation:

Natural selection favors the beneficial variations present in the population resulting in evolution of better adapted population /trait. Here, DDT resistance genes was present in the population. Mosquitoes with DDT resistance were able to survive and reproduce in presence of DDT. These mosquitoes were favored by natural selection. They transmitted the DDT resistance to their progeny leading to increase in their number in successive generations.