He coined the term ecology. He coined the term phylogeny. He coined the term ontogeny and propounded what he called the biogenetic law, asserting that the embryological development of an individual retraces the course of its evolutionary descent. A human embryo, by this argument, passes through stages at which it looks like the embryo of a fish, then of a salamander, then of a rabbit. Put in three words, as it would later be famously known: ontogeny recapitulates phylogeny.
