Phylum chordata

I NVERT EBRATE CH ORDAT ES ( NO BACK BONES) VERTEBRATE C H ORDAT ES

(H AVE BACK BONES )

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