Natural selection is a process where organisms with traits better suited to their environment tend to survive and reproduce, leading to changes in a population over generations.

A classic example is the peppered moth  in England. Before the Industrial Revolution, most peppered moths had light-colored wings, camouflaging them against lichen-covered trees. As pollution darkened the trees with soot, darker moths became better camouflaged and less likely to be eaten by birds. Over time, the population shifted to mostly dark-colored moths in polluted areas, illustrating natural selection in response to environmental changes.

Another example is antibiotic resistance in bacteria. When exposed to antibiotics, most bacteria die, but a few with resistance mutations survive. These resistant bacteria reproduce, and over generations, the population becomes predominantly resistant. This shows how natural selection favors traits that enhance survival under new conditions, whether it's pollution for moths or antibiotics for bacteria.

Both cases highlight how natural selection drives adaptation, allowing species to evolve traits that improve their chances of survival in changing environments.