• Animals Kingdom (Animalia)

• Cnidarians (Phylum Cnidaria)

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Phylum Cnidaria is a diverse group of mostly aquatic invertebrate animals that includes jellyfish, corals, sea anemones, hydroids, and related organisms. Found primarily in marine environments, with a few freshwater species such as the Hydra, cnidarians are characterized by radial symmetry, a simple body plan with a single opening serving as both mouth and anus, and specialized stinging cells called cnidocytes. These cells contain microscopic structures known as nematocysts that are used for prey capture, defense, and competition. Cnidarians occur in two basic body forms: the sessile polyp, exemplified by sea anemones and corals, and the free-swimming medusa, typified by jellyfish.