Alternation of Generations
Alternation of Generations, occurrence of two or more alternating forms in the life cycle of plants, algae, and among a small number of invertebrate animals. All plants take two generations to complete one life cycle. Among some algae, the two generations are similar in structure and appearance. In other plants, the two generations are fundamentally different. ... All plants undergo a life cycle that takes them through both haploid and diploid generations. ... The fluctuation between these diploid and haploid stages that occurs in plants is called the alternation of generations. The way in which the alternation of generations occurs in plants depends on the type of plant. ... Animals do not undergo alternation of generations that differ in chromosome number. The hydrozoa and other coelenterates undergo an alternation of generations between a colonial polyp form and a free-swimming medusa or other jellyfish form.