Changes
Common external factors include [[ultraviolet]] radiation, chemical [[mutagen]]s, or parasitic organisms (such as [[viruses]] or [[bacteria]]). Most internal causes of mutations stem from errors in reproduction of genetic material.
Some organisms will respond to harsh environments by increasing the rate of mutations. This is known as [[hypermutation]] and is hypothesized to aid organisms by creating wider variation in the [[gene pool]] of the population, increasing the chances that at least some descendents might survive under harsh conditions. Hypermutation also occurs in the human [[immune system]], so that our antibodies have more variation and can respond to a greater variety of invaders.
==Classes of mutations==
