Genetic diversity accounts for the difference in genes among individuals and species. Genetic diversity, or genetic variation, gives living organisms unique traits that distinguish them from even their closest relatives. Genetic variation explains differences in human facial features, breeds of dogs and cats, height and size of plants and many more alterations.
Over time, populations of species retain some common features while losing others. This phenomenon, called natural selection, promotes survival of the strongest genes. These genes give organisms better chances of surviving in specific habitats, reproducing and enjoying longer lives. This type of genetic variation produces differences in genes over an extended period of time, although genetic diversity occurs in the short-term too, altering the traits and characteristics between parents and offspring. Genetic variation occurs naturally, but humans create differences in genes too. This controlled selection takes place in several ways. Humans perform artificial selection, which isolates and promotes growth of ideal traits, in commercial areas such as aquaculture and commercial farming. People also eliminate problematic species and breeds from the plant and animal kingdoms, in turn promoting survival of the best genes. Humans sometimes cross-breed wild and domestic species of plants and animals, in turn varying genes. Artificial and natural genetic variation ultimately helps species survive by reducing risk of birth defects, disease and unfavorable genes.