alternation of generations

The occurrence of two or more reproductive forms during the life cycle of an organism. In plants it usually includes an asexual and a sexual phase resulting in alternating diploid and haploid individuals in the life cycle. In bryophytes the dominant generation is the *gametophyte, whereas in the pteridophytes and seed plants it is the *sporophyte. If the two generations are markedly different the life cycle is termed *heteromorphic whereas if they are similar it is termed *isomorphic . See also haplontic , diplontic , haplobiontic , diplobiontic.