Evolution

Variation

Organisms can vary in size, coloration, ability to fight off diseases, and countless other traits

Such variation is often the result of random mutations, or "copying errors," that arise when cells divide as new organisms develop

Since many traits are encoded in DNA, offspring often inherit the variations of their parents

Selection

Environments cannot support unlimited populations

Resources are limited, more organisms are born than can survive: some individuals will be more successful at finding food, mating or avoiding predators and will have a better chance to thrive, reproduce, and pass on, their DNA

Differences in color, for instance, aid some individuals in camouflaging themselves from predators. Sharper eyes and claws help an eagle catch its dinner. And brighter coloration improves a male peacock's chances of attracting a mate.

Time

In generation after generation, advantageous traits help some individuals survive and reproduce.

After just a few generations or after thousands, depending on the circumstances, such traits become common in the population

The result is a population that is better suited--better adapted--to some aspect of the environment than it was before.