How do protozoa differ from coelenterates?

The sub-kingdom of the simplest includes the smallest creatures, which have only one cell in the structure of the body. Each of these cells is an independent organism with its characteristic functions, namely: reproduction, movement, metabolism and irritability. But coelenterates are multicellular invertebrates that have organ systems. They do not have specialized respiratory and excretory organs, in the digestive system there is a mouth with an intestinal cavity. Representatives of the class of coelenterates are characterized by a special nervous system, which is based on the nerve plexus. However, planktonic forms are characterized by a fairly diverse sense organs around which nerve cells accumulate.