 However, adopting only an interbreeding approach to species has its costs: it would exclude all asexual organisms from forming species. Interbreeding requires the genetic contributions of two sexual organisms. Asexual organisms reproduce by themselves, either through cloning, vegetative means, or self fertilization. Some reptiles and amphibians reproduce asexually. Many insects reproduce asexually. And asexuality is rampant in plants, fungi and bacteria. In fact, asexual reproduction is the prominent form of reproduction on Earth (Hull 1988, Templeton 1989). If one adopts an interbreeding approach to species, then most organisms do not form species. This seems a high price to pay for species monism.