Consists of echinoderms that are a phylum of marine animals. Many of these well known animals are sea stars, sea urchins, and sand dollars. They can be found at any ocean depth and consist of about 70,000 species. It is the largest phylum with no freshwater or terrestrial representatives. They have a simple digestive system including a mouth, stomach, intestines, and an anus.
Star Fish
Their mouth is located on the underside of its body. They contain two stomachs, a cardiac and a pyloric one. Secrete enzymes and absorb nutrients from the food. Many star fish simply swallow their prey whole and begin to digest it without passing through the second stomach. In other species, the cardiac stomach everts out of the body and engulfs an organism and begins to digest it. The third way is to partially digest through the first stomach and then pass it on to the pyloric to finish the digestion.
Sea Urchin
The mouth is made up of five calcium carbonate teeth with a tongue-like structure inside the mouth. This chewing organ was named a lantern by Aristotle. The lantern surrounds both the mouth and the pharynx. There is an esophagus, small and large intestine, and a caecum. Digestion will occur in the intestine where the caecum produces digestive enzymes.
Brittle Star
The mouth contains five jaws and can serve as an anus as well. There is a short esophagus and a large stomach cavity. Digestion will occur within the ten pouches or infolds of the stomach. Usually eat small suspended organisms and in crowded, large areas brittle stars eat suspended matter from seafloor currents.