Phylum Chordata
 
Chordate Characteristics:
 
  • Notochord. All chordate embryos have a notochord, which is a longitudinal, flexible rod of cartilage located between the gut and the dorsal nerve cord. The notochord may persist into adulthood in some chordates, but in many it is replaced by the vertebral column. The spongy material in between the vertebral bones is all that is left of the notochord.
  • Dorsal Hollow Nerve Cord. The nerve cord of a chordate embryo is formed from a plate of dorsal ectoderm that rolls up into a tube. It is located dorsal to the notochord. This nerve cord is unique due to its hollow structure. It will develop into the chordate's central nervous system .
  • Pharyngeal Gill slits. These structures are openings of the upper digestive tube in chordates. The pharynx is the area just behind the mouth. During the embryonic stage of the chordates these slits connect the outside to the pharynx. Early chordates used them as devices for filter feeding. As time progressed the slits became modified to function in gas exchange.
  • Post anal Tail. Most chordates have a tail extending beyond the anus. In many aquatic species the tail is equipped with skeletal and muscular tissue for movement.
Subphyla of Chordata:
Subphylum Cephalochordata. These invertebrate chordates contain all 4 phylum characteristics in their adult body. The lancelet Brachiostoma is the characteristic organism of this group. The animal wiggles into the sand , leaving its anterior end exposed. It pulls in water through its mouth and traps the food on the mucus of its pharyngeal gill slits. It has limited movement, using a (~) sinusoidal pattern.
Subphylum Urochordata. The common organisms are called tunicates. Most are sessile marine organisms. The organism has a body plan similar to that of a clam. Water is drawn into the body through an incurrent siphon; food particles are filtered out through the mucus covered gill slits. The food then moves into the intestine and the waste material is then passed out through the excurrent siphon. The adults lose 3 of the chordate characteristics as adults: Notochord, nerve chord , and tail.
 

Subphylum Vertebrata.
Cephalization, development of highly specialized sensory structures and a highly specialized brain.
Vertebral column, The axial skeleton ( skull, ribs, and vertebra ) and the appendicular skeleton ( arms and legs, or wings, or flippers ) is an internal living system.
Closed circulatory system. It is a closed system. The heart is composed of a collecting chamber(s) and a pumping chamber(s). The cells of the body exchange food and gases through tiny blood vessels called capillaries.
The kidney is the main excretory organ.
Sexes are separate. Fertilization may be internal or external depending on the species.
Respiratory organs include the gills, lungs, or highly vascularized skin. Oxygen is carried to all parts of the body in a liquid called blood. Hemoglobin is the main attractant of oxygen and is found in the red blood cells.
 
Class
Main Characteristics
Examples

Agnatha

jawless, cartilage skeleton,gill slits, no swim bladder

Lamprey and Hagfish

Chondrichthyes

Placoid scales, cartilage skeleton internal fertilization, paired fins,

Sharks, Rays, and Skates

Osteichthyes

Bony skeleton, paired fins, operculum, swim bladder

Tuna, Bass, Catfish, Flounder

Amphibia

Smooth skin, no claws, aquatic larvae, breathe through lungs and skin

Frog, Salamander, and Toad

Reptilia

Amniote egg, rough,dry skin, respiration through lungs

Snakes, Lizards, Turtles, and crocodiles

Aves

Feathers, amniote egg, extensive lung system, and wings

Birds

Mammalia

Hair, diaphragm, mammary glands, and bear live offspring.

Marsupials, monotremes, and Placentals