Heritable variation is variation caused by genetic material that can be passed on to the next generation. There are two main categories of variation, heritable variation and non-heritable variation. Heritable variation is variation caused by changes in the genetic material, while non-heritable variation is caused by the environment, with no change in the genetic material. There are three main sources of heritable variation, including genetic recombination, genetic mutation and chromosomal variation, all of which are theoretically heritable because they change the genetic material. Heredity and variation are two concepts. Heredity and variation are a pair of contradictions in life activities, both opposing and unifying; heredity is relative and conservative, while variation is absolute and developmental. Without heredity, it is impossible to maintain the relative stability of species. Without variation, it would be impossible for new species to be formed and for a colorful and diverse biological world to exist today.