Question

One of the problems associated with pesticide use is the development of resistance. The first year that a farmer uses a pesticide on their crops, they see a great result: the insects are killed, and crop yield is increased. However, as the same pesticide is used year after year, it seems to have less and less effect on the population. Why does this happen?

Below are three possible explanations: post in your answer which one you think is correct. (It’s totally ok to have the same answer as other group members. Be sure to check back after the deadline to see if your answer was correct!

1. When humans use pesticides, it causes mutations in the genes of the insects that allow them to survive the pesticide. If we use the pesticide a lot, pretty soon all of the insects will develop that mutation.

2. A very small number of insects in a population have a mutation that makes them less susceptible to the pesticide. When we use the pesticide a lot, we kill off the majority of insects that don’t have the mutation, and the only insects that survive and breed are those with the mutation that makes them resistant.

3. Insects exposed to a pesticide would, over time, build resistance to the pesticide. If two of these insects mate together, their offspring would be even more resistant to the pesticide.

Answer 1

Answer: Option 2

A very small number of insects in a population have a mutation that makes them less susceptible to the pesticide. When we use the pesticide a lot, we kill off the majority of insects that don’t have the mutation, and the only insects that survive and breed are those with the mutation that makes them resistant.

Explanation:

As the pesticide kills most of the insects the first time, the only small number of insects which survive will reproduce. And these are resistant to the pesticide, hence as the same pesticide is used year after year, it seems to have less and less effect on the population.