Question

4.c - unit b: natural selection assessment
spraying insects with a pesticide such as ddt causes some pesticide resistance in insect populations. the changes that occur in the insect population are related to a pattern of genetic inheritance. repeated spraying kills many insects; however, more frequent spraying and higher concentrations fail to kill all the insects. in this environment, the spraying of the insecticide appears to act as
○ a growth inhibitor
○ a biological barrier
○ an agent of selective pressure
○ an agent to eliminate old and weak insects

Explanation:

When a pesticide like DDT is sprayed, insects without resistance die, while those with resistance survive and reproduce. This is natural selection, where the pesticide acts as a selective pressure (factor that affects survival/reproduction) favoring resistant insects. A growth inhibitor stops growth, a biological barrier is for isolation, and eliminating old/weak isn't the main role here—selective pressure drives genetic change via survival of resistant traits.

Answer:

an agent of selective pressure