The process by which organisms that are better suited to their environmentthan others produce more offspring. As a result of natural selection, theproportion of organisms in a species with characteristics that are adaptiveto a given environment increases with each generation. Therefore, natural selection modifies the originally random variation of genetic traits in aspecies so that alleles that are beneficial for survival predominate, whilealleles that are not beneficial decrease. Originally proposed by Charles Darwin, natural selection forms the basis of the process of evolution.

Examples-

• In a habitat there are red bugs and green bugs. The birds prefer the taste of the red bugs, so soon there are many green bugs and few red bugs. The green bugs reproduce and make more green bugs and eventually there are no more red bugs.
• In an ecosystem, some giraffes have long necks and others have short ones. If something caused low-lying shrubs to die out, the giraffes with short necks would not get enough food. After a few generations, all the giraffes would have long necks.
• A species of rats live in a certain type of tree with the branches evenly spaced. Smaller rats could not reach from branch to branch and larger rats would break the branches and fall. Soon, all rats were just the right size for the tree branches.
• Deer mice that migrated to the sand hills of Nebraska changed from dark brown to light brown to better hide from predators in the sand.