heterogony

Heterogony (from Greek heteros “different” and gony “generation”) is a biological term describing life cycles that include two or more successive generations that differ in form, and often in ploidy or reproductive mode. The generations alternate; one may be haploid and produce gametes, while the other is diploid and produces spores, or they may occupy different habitats or hosts. The concept is used across botany, mycology, protozoology, and parasitology.

In plants and algae, heterogony often refers to heteromorphic alternation of generations, where sporophyte and gametophyte are morphologically distinct. Many brown algae and several bryophytes and pteridophytes show such differences, with a clearly different morphology in the sporophyte versus the gametophyte. In flowering plants, the two generations may differ markedly, for instance, the dominant sporophyte in angiosperms and the microscopic, dependent gametophytes.

In parasitology, heterogony can describe life cycles that alternate between sexual and asexual generations or between different hosts or environments; an example is the malaria parasite Plasmodium, which undergoes sexual development in a mosquito vector and asexual replication in a vertebrate host. The term is related to, though distinct from, broader concepts such as alternation of generations and metagenesis.