Phylum Chordata

Characteristics of all chordates Dorsal, hollow nerve cord Post-anal tail Gill pouches at some time in the live Notochord The most complex of the animals Most, but not all, have backbones

Characteristics  Notochord Longitudinal flexible rod of cartilage located between gut and dorsal nerve cord Persists into adulthood in some chordates In many it is replaced by vertebral column Spongy material between vertebral bones is remnant of notochord

Characteristics  Dorsal Hollow Nerve Cord In embryo, formed from a plate of dorsal ectoderm that rolls up into a tube Located dorsal to notochord Unique due to its hollow structure Develops into chordate’s central nervous system

Characteristics  Pharyngeal Gill Slits Openings of the upper digestive tube in chordates Pharynx is area just behind mouth During embryonic stage of chordates these slits connect the outside to the pharynx Early chordates used them as devices for filter feeding Evolved and became modified to function in gas exchange

Characteristics  Post Anal Tail Most chordates have tail extending beyond the anus Many aquatic species have tail equipped with skeletal and muscular tissue for movement.

Taxonomy of Chordates Taxonomy- the study of classification

Phylum Chordata Subphylum Urochordata Subphylum Cephalochordata Subphylum Vertebrata Superclass Fishes Class Agnatha Class Chondrichthyes Class Osteichthyes Class Amphibia Class Reptilia Class Aves Class Mammalia

Subphylum Urochordata  Tunicate-sea squirt are most popular example for study  Larva has all four chordate characteristics  Retain only gill slits in adult Most are marine No backbone

Subphylum Cephalochordata  Small marine animals just a few cm. long  Lancelets-blade shape  All four chordate characteristics persist in adult  No backbone

Subphylum Vertebrata  Additionally, they demonstrate Cephalization Vertebral column (backbone) as part of endoskeleton Closed circulatory System Show all four chordate characteristics at some time in their life.

Superclass Fish  Characteristics- Primitive No jaws Cartilaginous skeleton Scaleless skin Oral sucker in place of jaws Predators and filter feeders Anticoagulating saliva Fresh and salt water  Examples Lamprey hagfish Class Agnatha

Class Chondrichthyes  Cartilaginous skeleton  Skin covered with denticles, not scales  Five to seven gill slits per side  No swim bladder  Internal fertilization  Spiral valve intestines  Five to seven gill arches Examples: sharks rays

Class Osteichthyes Bony Fish  Largest group of vertebrates  Calcified skeleton  Great maneuverability  Swim bladder for control of buoyancy