The answer is alternation of generation. It occurs in those plants and algae in the Archaeplastida and the Heterokontophyta that have distinct sexual haploid and asexual diploid stages. The relationship between the sporophyte and gametophyte varies among different groups of plants. In those algae which have alternation of generations, the sporophyte and gametophyte are separate independent organisms, which may or may not have a similar appearance. In liverworts, mosses, and hornworts, the sporophyte is less well developed than the gametophyte and is largely dependent on it. In all modern vascular plants the gametophyte is less well developed than the sporophyte.