Genetic diversity is a level of biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary. Research has found that genetic diversity and biodiversity are dependent upon each other, that diversity within a species is necessary to maintain diversity among species, and vice versa. If any one type is removed from the system, the cycle can break down, and the community may become dominated by a single species. Thus, genetic diversity plays a huge role in survival and adaptability of a species. This book provides research on genetic diversity in plant, animal and human species. Relationships to environment changes and global warming are also studied.