Polymorphism is a characteristic of members of phylum:

Explanation

Polymorphism is a characteristic found in members of the phylum Cnidaria. Cnidaria is a diverse group of aquatic invertebrates that includes jellyfish, corals, sea anemones, and hydroids. One of the defining features of cnidarians is their possession of specialized stinging cells called cnidocytes, which contain nematocysts used for capturing prey and defense. Polymorphism in cnidarians refers to the existence of different body forms within a single species. Many cnidarians exhibit two or more distinct morphological forms, each specialized for different functions or stages of their life cycle.