The Chordate Animals

Neotony Evolutionary process in which adolescent characteristics are selected for (adults against) such that species become young looking while maintaining the adult ability to reproduce

Chordate Characteristics Notocord Dorsal Nerve Cord Pharyngeal Slits Postanal Tail

Notocord Rodlike semi-rigid body of cells enclosed by a fibrous sheath and filled with fluid Functions to support and stiffen the body for movement

Dorsal Nerve Cord Dorsal to the Notocord this structure may develop an anterior brain Functions to integrate sensory stimuli and to control muscular response

Pharyngeal Slits Filter feeding anatomy in ancestral chordates that becomes associated with gills in later aquatic forms.

Other Chordate Characteristics Mainly Bilateral and Cephalized Deuterostome Coelomate Segmented Endoskeleton

Chordate Classification Subphylum Urochordata (Tunicates) Subphylum Cephalochordata (Lancelets) Subphylum Vertebrata (Vertebrates)

Urochordates (Tunicates) Marine and mainly non-mobile filter feeding organisms (sponge-like) Contains chordate characteristics during the larval stage of its life cycle

Cephalochordates (Lancelets) Marine mobile filter feeding organism (fish-like) Contains chordate characteristics during its adult stage

Vertebrates Common Chordate Animals Backbone replaces Notocord Pharyngeal Bones evolve into Jaws Lungs and Four Appendages (Tetrapods) Evolve

Diverse Fishes 1) Jawless Fish (Class Agnatha) 2) Cartilaginous Fish (Chondrichthyes) 3) Bony Fish (Osteichthyes) Characterized by scales, predatory lifestyle, and a swimbladder

Amphibians (Class Amphibia) Vertebrates characterized by smooth moist skin, an amphibious lifestyle and metamorphosis Gilled larvae that are highly aquatic Adults having lungs that are more terrestrial Salamanders, Frogs, and Toads

Reptiles (Class Reptilia) Vertebrates characterized by scales, internal fertilization, and an amniotic egg Turtles, Crocodiles, Snakes, and Lizards

Birds (Class Aves) Vertebrates characterized by feathers, flight, warm-bloodedness, and parental care

Mammals (Class Mammalia) Vertebrates characterized by hair, various skin glands including the mammary gland, internal placental development, and heterodont teeth