How does pesticide resistance arise in a pest population?

• A. Random mutations only
• B. Hybridization with crops
• C. Natural selection
• D. Pesticides always kill all

Answer: (C)

Natural selection is the process behind pesticide resistance. In any pest population there is genetic variation, including traits that can help some individuals tolerate a pesticide. When the pesticide is applied, susceptible pests die while those with resistance survive and reproduce. Their offspring inherit the resistant traits, so the proportion of resistant individuals grows in the population over generations. Over time, the population becomes less affected by the same pesticide. Random mutations provide the variation that selection acts on, but it's the differential survival and reproduction under pesticide pressure that drives the increase in resistance. Hybridization with crops isn’t how resistance to chemicals arises, and pesticides don’t always kill every pest, so survivors can and do shape the population’s response.