Obligate parthenogenesis is the process in which organisms exclusively reproduce through asexual means. Many protists and fungi alternate between sexual and asexual reproduction. Amoeba have generally been regarded as asexual protists. A form of asexual reproduction related to parthenogenesis is gynogenesis. Organisms that reproduce through asexual reproduction tend to grow in number exponentially. It has been speculated that Sheldon may be asexual or aromantic. They reproduce by forming asexual and sexual spores. Reptiles generally reproduce sexually, though some are capable of asexual reproduction. Both vegetative (asexual) and seed reproduction occur. Plants have a number of mechanisms for asexual or vegetative reproduction. Sclerotia germinate to produce additional hyphae and asexual spores call conidia. Many algae similarly switch between sexual and asexual reproduction. Some organisms can also reproduce by themselves in a process known as asexual reproduction. Fungi commonly produce spores, as a result of sexual, or asexual, reproduction. Both sexual and asexual reproduction can occur.