PHYLUM CHORDATA
INVERTEBRATE CHORDATES (NO BACKBONES)
VERTEBRATE CHORDATES (HAVE BACKBONES)
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
• Condricthyes: 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
AMPHIBIANS
• Vertebrates that are aquatic as larvae
and terrestrial as adults
• Have moist skin, lack scales and claws,
and adults breath with skin and lungs
• Smallest vertebrate class (4000
species)
• It has three orders:
• Frogs and toads (order ANURA)
• Salamanders and newts (order CAUDATA)
• Legless amphibians (order APODA)
REPTILES
• Vertebrates with adaptations that enable
them to live entirely on land
• Have lungs that are more efficient than
amphibians, scaly skin to prevent drying out,
amniotic egg with shell, yolk and several
protective membranes
• 4 orders
• Snakes and lizards
• Crocodilians
• Turtles, tortoises + terrapins
• Tuataras (last species of an order common in
time of dinosaurs)
BIRDS
• Reptile like vertebrates with the following
modifications:
• Feathers
• Front limbs modified into wings
• Hind limbs for perching/walking
• Birds are as successful as mammals in the
modern world. (live almost in all habitats)
• Many orders: songbirds, waterfowl,
raptors, seabirds, penguins and flightless
birds