INVERTEBRATE CHORDATES (NO BACKBONES) VERTEBRATE CHORDATES (HAVE BACKBONES) PHYLUM CHORDATA

ALL CHORDATES HAVE THE FOLLOWING: Notochord: Flexible dorsal supporting rod Usually replaced by a backbone as embryo develops Hollow dorsal nerve cord As opposed to the ventral nerve in other animals Pharyngeal (throat) slits In aquatic chordates, these gills are slits In terrestrial chordates, these slits disappear early in embryonic development

INVERTEBRATE CHORDATES Tunicates and lancelets Not many of these but they are of great evolutionary interest Possible link between vertebrates and all other animals

VERTEBRATE CHORDATES Fish (3 classes) Amphibians Reptiles Birds Mammals

VERTEBRATES (SUBPHYLUM VERTEBRATA) Characteristics: Endoskeleton Vertebral column (“backbone”) Closed circulatory system Ventral heart Usually four appendages

TEMPERATURE CONTROL All vertebrates must keep their body temperatures within a certain range. There are 2 ways of doing this Ectotherms: change behavior in response to temperature fluctuations Lack effective insulation, have low metabolic rates, are fish, amphibians, reptiles Endotherms: rely on heat generated by their bodies (and some behavioral strategies) They have insulation, high metabolic rates, birds, mammals and possible dinosaurs

FISH Aquatic vertebrates with scales, fins and pharyngeal gills Classes: Agnatha : primitive jawless fish that are parasitic or scavegers, includes lampreys and hagfish Chondricthyes : ancient group of mostly predatory cartilaginous fish (skeleton entirely cartilage), includes sharks, skates and rays Osteichthyes: “regular” fish with a bony skeleton. 97% of all fish are in this class