<em>Compounds like the pesticide DDT may bring about the evolution of new strains of organisms by </em><em><u>acting as a natural selecting agent.</u></em>
Evolution is generally defined as a gradual change to the characteristics of organisms over a period of time.
<u>When DDT is used on a particular population of pest, those that are weak within the population die off, leaving only those that are strong within the population to survive and multiply. The DDT acts a selecting agent for the survival gene in the pest and the survived gene eventually evolve into a new, DDT-resistant strain pest in no time.</u>
