<P> In biology, a biological life cycle (or just life cycle when the biological context is clear) is a series of changes in form that an organism undergoes, returning to the starting state . "The concept is closely related to those of the life history, development and ontogeny, but differs from them in stressing renewal ." Transitions of form may involve growth, asexual reproduction, or sexual reproduction . </P> <P> In some organisms, different "generations" of the species succeed each other during the life cycle . For plants and many algae, there are two multicellular stages, and the life cycle is referred to as alternation of generations . The term life history is often used, particularly for organisms such as the red algae which have three multicellular stages (or more), rather than two . </P>

Phases of life cycle in plants which alternate with each other