Most are aquatic, found in both fresh water and in the oceans. Includes crayfish, lobsters, barnacles, crabs, shrimp. Uniramia Get their name from their unbranched appendages . Body segments grouped into head , thorax , and abdomen . Gas exchange through a tracheal system.
Nitrogenous waste is uric acid thus conserving water.
Dominate all habitats except for the oceans. The features of these animals are listed above . The group comprises the echinoderms and the chordates . Seawater is taken into a system of canals and is used to extend the many tube feet . These have suckers on their tips and aid the animal in attaching itself to solid surfaces.