What characteristics did cnidarians add and what do these additions allow cnidarians to do?

Cnidarians, such as jellyfish, corals, and sea anemones, developed specialized cells called cnidocytes, which contain stinging organelles (nematocysts) that allow them to capture prey and defend against predators. They also possess a simple body plan with radial symmetry and a gastrovascular cavity for digestion. These characteristics enable cnidarians to efficiently interact with their environment, providing them with enhanced predatory capabilities and a means of protection, which contributes to their success as aquatic organisms.