 Includes all vertebrates and two groups of invertebrates  Have four characteristics during some stage of their life;  Notochord  Dorsal nerve chord  Pharyngeal pouches/gill slits  Postanal tail

 Is a stiff flexible rod of cells that runs dorsally the length of the body  provides a strong surface for muscles to attach  usually present in the embryo of vertebrates but becomes reduced when the backbone develops

 is a hollow tube where the anterior end enlarges to form the brain and the posterior end forms the spinal cord

 out pockets in the pharynx develping into gills for aquatic organisms and jaws, inner ear, tonsils for terrestrial organisms

 Aquatic chordates possess this characteristic as an adult  acts as a form of propulsion in the water

 Deuterostomes  Coelomates  Divided into three subphyla:  Vertebrata (95% of all chordate species)  Cephalochordata  Urochordata

 Includes lancelets  Keep notochord, dorsal nerve chord, pharyngeal pouches, and postanal tail  They live in warm, shallow waters where they wiggle backwards into the sand.  Cilia pull water into their pharynx where food is trapped in the slits entering the intestines to be digested.

 Includes sea squirts (tunicates)  Bodies are covered with a thick tough covering called tunic.  Sessile barrel-shaped animals that live on the bottom of the sea.  Larval forms possess all four chordate characteristics but loose them during metamorphosis.  As adults they have a pouch-like pharynx with slits, are filter-feeders and hermaphrodites.

 at some stage they have a notochord, dorsal nerve chord, pharyngeal pouches, and a postanal tail  distinguished from other subphyla by three characterisitics;  Vertebrae  Cranium  endoskeleton of bone or cartilage

 Class Agnatha (lampreys and hagfish),  elongated eel-like bodies, lack jaws, paired fins, and bone  Class Chondricthyes (sharks, rays, and skates)  predatory fish have jaws and paired fins, their skeleton is made of cartilage, skin is covered in a unique scale  Class Osteichthyes (bony fish)  they have jaws, boney skeleton  Class Amphibia (Amphibians)  skin is thin, lay eggs in water and have an aquatic larval stage

 Class Reptilia (Reptiles)  skin is dry and scaly, eggs are laid on land and protect the embryo from drying out  Class Aves (Birds)  they have adapted for flight through wings, hollow bones, unique respiratory system  Class Mammalia (Mammals),  they grow hair and nurse their young