Alternation of generation

Alternation of generations is the type of life cycle that occurs in those plants and algae in the Archaeplastida and the Heterokontophyta that have distinct sexual haploid and asexual diploid stages

a pattern of reproduction occurring in the life cycles of many lower plants and some invertebrates, involving a regular alternation between two distinct forms. The generations are alternately sexual and asexual (as in ferns) or dioecious and parthenogenetic (as in some jellyfish).