Noun
1. A period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction (a period from one generation of organisms to the same identical). (wikipedia.org)
2. The course of stages through which an organism passes from fertilized zygote until maturity, reproduction, and death. (wiktionary.org)
3. The whole life history of an organism, usually depicted through a series of developmental stages (e.g. from zygote into a mature form where another zygote can be produced) in which an organism goes through. (biology-online.org)