All of the animals in the Phylum are aquatic. Most are marine, but a few, like Hydra live in freshwater. However, unlike the sponges in which the cells are independent of one another, the cells of animals in the Cnidaria are organized into tissues.
Tissues are groups of closely associated similar cells that carry out carry out a specific function.
Examples of tissues are muscle tissue or nerve tissue. The animals in the Phylum Cnidaria have radial symmetry. This means that, while the animal has a digestive cavity that allows it to ingest relatively large prey, there is only one opening to the gvc. The food eaten by Hydra and other animals in the Phylum Cnidaria is other animals. Animals that eat other animals are called carnivores.