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. It encompasses all the changes that occur in an organism's structure and function over time. The study of ontogeny is important in fields like biology and developmental psychology, as it helps scientists understand how organisms grow and adapt. By examining ontogeny, researchers can gain insights into evolutionary processes and the relationships between different species, including how traits are inherited and expressed throughout an organism's life.