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. About 6,000 species - all of them marine. At its anterior end, it becomes enlarged to form the brain . In vertebrate chordates, it is replaced by a vertebral column or backbone long before maturity. These lateral outpocketings of the pharynx are matched on the exterior by paired grooves.