Different animals undergo unique life cycles, some experiencing metamorphosis—a series of developmental changes. Complete metamorphosis (holometabolous) includes egg, larva, pupa, and adult stages (e.g., houseflies, butterflies), while incomplete metamorphosis (hemimetabolous) involves egg, nymph, and adult stages (e.g., cockroaches, grasshoppers). Amphibians like frogs experience both aquatic and terrestrial phases, while mammals have direct development from embryo to adult.