ABSTRACT
In animals, as in eukaryotic plants, sexual reproduction prevails, and recombination is associated with meiosis. Asexual reproduction by division, or budding, is common among Protozoa and Coelenterata, where sexual reproduction also takes place. Parthenogenetic reproduction is known from several animal groups. Its general genetic and evolutionary consequences are similar to those of apomixis in plants: it allows for multiplication of fit biotypes, but limits the potential for genetic recombination. Parthenogenesis is a condition derived from sexual reproduction, in which an egg cell develops into a new individual without fertilization. Facultative apomixis is common in plants, where an individual often has the capacity both for apomictic and sexual reproduction. A classic tradition of studies of experimental parthenogenesis exists in insects. Polyploid forms occur especially in animals with apomictic parthenogenesis. Animals with cyclical parthenogenesis have access to the advantages of both sexual and parthenogenetic reproduction. The evolutionary potential of parthenogenetic groups has been considered very restricted, to say the least.
