Exposure to a selection pressure, such as an herbicide or antibiotic, is what causes a new trait to appear in a population.

a. True

b. False

A. True

Explanation:

We continuously use drugs and antibiotics against the micro organisms. In the course of time, some microbes may develop resistance against these antibiotics by bringing changes or modifications in their structures. Those which become resistant, survive the selective pressure and hence selected by the nature. Hence developing drug resistance by microbes is also an example of natural selection.

Similarly herbicides and pesticides resistance developed in weeds and pests respectively after prolonged use of herbicide and pesticide is also an example of natural selection which supports the process of evolution.