Peppered moth:
* two varieties of peppered moth existed, a light colored and a dark colored one

-as industrialization and coal burning increased, the environment in England where these moths lived became dirtier.

-the dark colored variety of the moth blended into the trees and increased in numbers, while the light colored moth was less adapted and decreased in numbers Insect resistance to insecticides

* Insecticides kill insects not resistant to the insecticide, while insects resistant to the insecticide live to reproduce. The insecticide acts as a selecting agent.

Bacterial resistance to antibiotics:
* Bacteria not resistant to an antibiotic are killed by it, while resistant bacteria live to reproduce. The antibiotic is a selecting agent for these bacteria.