Coelenterates are also called cnidarians. Coelenterates include corals, hydra, jellyfish, Portuguese man-of-war, and sea anemone. There are alot of species (more than 9,000, probably estimated by maybe 9,000+ or more). They usually live in oceans but some live in freshwater habitats.
Coelenterates have a circular or radial symmetry. Their structure is such that even they are small, they can still be divided into 4 parts or 6 vertically similar parts or segments. Their tissue structure may be thin or firm, gelatinious which can contain the nerve, the muscle, and their skeletal structure of the species found in all oceans.
Coelenterates are animals with hollow and soft bodies. Some use tentacles, specifically squids and octopus.
Worms can be classified as roundworms, segmented worms, or flatworms.
Roundworms have tubelike, slender bodies. They have an opening at each end --- the mouth and anus.
Segmented worms have bodies that are divided into sections. The earthworm is a good and a common example for this.
As the name suggests, these worms are flat. They have soft- structured bodies with only one opening.
Echinoderms are spiny skinned animals that usually have a five part radial symmetry.v Examples are starfish, sea cucumbers, and sea urchins.
Mollusks are soft bodied animals. Some have enclosed in shells for protection.
The snail has a shell that is secreted by a sheet called the mantle. The mantle forms the spiral like part of the shell.
Clams, oysters, scallops, and mussels are bivalve mollusks. Their shells are hinged together. They have long siphons that are used for getting water to sustain moisture in their bodies to survive.
Arachnids are invertebrates with eight legs and two main body regions, the cephalothorax and the abdomen.