Ontogeny refers to the development of an individual organism from the earliest stages of life to maturity. This process includes various stages such as fertilization, embryonic development, and growth, ultimately leading to the adult form. Understanding ontogeny helps scientists study how organisms change and adapt over time. The concept of ontogeny is often contrasted with phylogeny, which is the evolutionary history of a species. While ontogeny focuses on individual development, phylogeny examines how species evolve and relate to one another. Both concepts are essential in the fields of biology and evolutionary science.