Ontogeny (also ontogenesis or morphogenesis) is the origination and development of an organism, usually from the time of fertilization of the egg to the organism's mature form—although the term can be used to refer to the study of the entirety of an organism's lifespan.
Ontogeny is the developmental history of an organism within its own lifetime, as distinct from phylogeny, which refers to the evolutionary history of a species. In practice, writers on evolution often speak of species as "developing" traits or characteristics. This can be misleading. While developmental (i.e., ontogenetic) processes can influence subsequent evolutionary (e.g., phylogenetic) processes (see evolutionary developmental biology), individual organisms develop (ontogeny), while species evolve (phylogeny).
Ontogeny, embryology and developmental biology are closely related studies and the terms are sometimes used interchangeably. Recently (2003), the term ontogeny has been used in cell biology to describe the development of various cell types within an organism.
Ontogeny is a useful field of study in many disciplines, including developmental biology, developmental psychology, developmental cognitive neuroscience, and developmental psychobiology.
Ontogeny is also a concept used in anthropology as "the process through which each of us embodies the history of our own making".
The word ontogeny comes from the Greek , on (gen. ὄντος, ontos), i.e. "being; that which is", which is the present participle of the verb , eimi, i.e. "to be, I am", and from the suffix -geny from the Greek -γένεια -geneia, which expresses the concept of "mode of production".