This type of reproduction increases the genetic variability of the species. It is advantageous in environments that are under constant stress. Some lower forms of invertebrates contain both sexes in the same body. This is called hermaphroditism. This allows the organism who has difficulty finding a suitable mate the chance to reproduce.
Many hermaphrodites exchange sperm with a mate increasing the potential of producing offspring.
Another form of sexual reproduction is parthogenesis. Parthogenesis is the development of an egg without fertilization. Adults developed by parthogenesis are haploid. Some social insects develop in this way. Sequential hermaphroditism occurs in some species.