Ontogenie

Ontogenie, or ontogeny in English, is the developmental history of an individual organism from fertilization to maturity, including embryonic development, post-embryonic growth, and aging. The term derives from Greek ontos “being” and genesis “origin.”

Biology uses ontogeny to refer to the processes by which a zygote becomes a fully formed organism. Key stages include embryogenesis, cell division and differentiation, morphogenesis, organogenesis, growth, and senescence. Development is controlled by gene regulatory networks, signaling pathways, and epigenetic modifications, and it is modulated by environmental conditions and mechanical constraints. The timing of developmental events, or heterochrony, can influence form and function and has implications for evolution.

Ontogeny is often contrasted with phylogeny, the evolutionary history of a lineage. The biogenetic law, once claimed that ontogeny recapitulates phylogeny, has been discredited, though ontogenetic stages can reflect evolutionary history and homologous structures.

Across life forms, ontogeny follows characteristic patterns: animals undergo embryogenesis and, in many groups, metamorphosis; plants develop from zygotes into shoots, roots, leaves, and flowers; these processes involve conserved genetic programs but diverge to yield diverse life forms.

Studying ontogeny informs fields from developmental biology and genetics to paleontology and medicine, shedding light on congenital disorders, growth disorders, regenerative biology, and the plasticity of development.