Natural Selection and Evolution

In 1835 Charles Darwin traveled to the Galapagos Islands and was intrigued by the various species he observed.

Darwin observed differences in the beaks among the species of finches on the islands. Each beak was an adaptation suited for the type of food each species of finch ate.

An adaptation is a trait that helps an animal survive in its environment.

A variation is any difference between individuals of the same species. Species Variation A variation is any difference between individuals of the same species.

Variations can help some members of a species survive while others die.

More members of a species are born than can survive More members of a species are born than can survive. Some variations make certain individuals better adapted to their environment; those individuals are more likely to survive and reproduce.

Because of competition, some of these animals might not find enough to eat, some might not be able to escape from predators, some may lose in fights with other animals.

Natural selection is the process by which individuals that are better suited to their environment are more likely to survive and reproduce than other members of the same species…

…over a long period of time, natural selection can lead to evolution.

More and more members of a species will have a helpful trait (the environment has “selected” organisms with helpful traits to be the parents of the next generation). Helpful variations gradually accumulate in a species while unfavorable ones disappear.

Extinction occurs when the environment changes and the adaptive characteristics of a species are insufficient to allow its survival.