The Chordates………
• Invertebrate chordates
– Tunicates and lancelets
• Vertebrate chordates
– Fishes
– Amphibians
– Reptiles
– Birds
– Mammals
Nonvertebrate Chordates
• Tunicates (sea squirts)
– Squirt water when their siphons
are disturbed
• Live in ocean and are filter-feeders
• Larva is bilaterally symmetrical and
has four chordate characteristics
• Adults are sessile, thick-walled, saclike organisms
– The only chordate
characteristics in the adults are
pharynx and gill slits
Vertebrates
• Characteristics
– Have four chordate
characteristics at some point in
life
– Distinguishing features
• Strong, jointed endoskeleton
• Vertebral column composed of
vertebrae
• Closed circulatory system
• Efficient respiration and excretion
• High degree of cephalization
Milestones….
• Vertebrate chordates
– Fishes, amphibians, reptiles, birds,
mammals
• Cartilaginous fish
– First to develop jaws
– Some early bony fish had lungs
• Amphibians
– First to have jointed appendages and
invade land
• Reptiles, birds, mammals
– Terrestrial adaptations for reproduction
• Fishes: First Jaws, Then Lungs
• Adapted to life in water
Fishes
– Sperm and eggs released into water
– Fertilization external
– Zygote develops into swimming larval
form
•
•
•
•
•
Fish vs Fishes???
Lateral line system
Body streamlined for life in water
Vary buoyancy
VERY efficient at extracting
oxygen from water
Fishes
• 2 chambered heart
• Ectothermic
• What are fish?
– Jellyfish?
– Starfish?
– Crayfish?
– Shellfish?
• Three main groups/classes of fishes
– Jawless fishes
– Cartilaginous fishes
– Bony fishes
Fish
Fishes
• Jawless Fishes
– Cylindrical body shape with smooth, scaleless skin
– No jaws, no paired fins
– Hagfish are scavengers
– Lampreys are parasitic
• Mouth modified to form a sucker
• Attach to other fish
• Water moves in and out of gills directly and not through mouth as
in other fish
• Cartilaginous fishes
Fishes
– Sharks, skates, rays
– Skeleton comprised of
cartilage
– Ability to sense electric
currents in the water
– Keen sense of smell
– Sharks lack a swim bladder
• Oily liver is ¼ body size!
• 4 ton shark = 1 ton liver
• Also serves as fat reserves since
no blubber
http://www.youtube.com/watch?v=O2FInaOCqoo
Fishes
• Bony fishes
– Cod, trout, salmon
– Ossified internal
skeleton
– Some have lung-like
anatomy
– Some give birth to live
young
• Jointed appendages
Amphibians
• Class Amphibia
–
–
–
–
–
–
–
“two lives”
Tetrapods
Eyelids keep eyes moist
Have ears
Larynx for vocalization
Larger brain than in fish
Small lungs present in adults
• Gas exchange also occurs
across moist skin
– Three-chambered heart• Two atria and a ventricle
Amphibians
• Moist skin
• Poison and mucous
glands
• Ectothermic
• Large mouths and
consume prey whole
Amphibians
• Have either internal or external fertilization
• Metamorphic life cycle
– Aquatic larva (gills) - water
– Terrestrial adult (lungs) - land
Class Amphibia – 3 Orders
• Order: Gymnophiona
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–
–
–
Caecilians
Lack limbs
Ossified heads
Burrowing
Class Amphibia – 3 Orders
• Order: Caudata
–
–
–
–
Salamanders and Newts
Long tails
Limbs**
Diversified habitats
Class Amphibia – 3 Orders
• Order: Anura
– Frogs and toads
– Tailless
– Continuous head and
body
– Well developed limbs
– Saltatory locomotion
http://www.youtube.com/watch?v=wXqK5QulbJ8
• Amniotic egg
Reptiles
• Class Reptilia
– Turtles, tortoises, snakes,
lizards, crocodilians
– Body is covered with scales to
protect against desiccation
and also against predators
– Ectothermic
• Use 90% less calories!
– Eyelids
• Well-developed sense
Reptile
organs
– Snakes have tongue
modified as sense organ
– Crocodilians have ISO
– Tuataras have third eye!!!!
• Well developed lungs
protected by a rib cage
• Three-chambered heart
(division between
ventricles is usually
incomplete)
– Always?!?!
Reptiles
• Amniotes
–
–
–
–
Tetrapods that have a terrestrially adapted egg
Amniotic egg usually buried in substrate
Contains membranes that protect the embryo
In reptiles, internal fertilization
Reptile
• Temperature-dependant sex
determination
• Cloacal opening (vent)
• Full-body ecdysis
• Some have limb reduction
common
– Caudal autotomy
Class Reptilia – 4 Orders
• Order: Testudines
– Turtles and tortoises
– Carapace and plastron
Class Reptilia – 4 Orders
• Order: Crocodilia
–
–
–
–
Crocodilians
Semi-aquatic
Bony armor
Great parental care of
eggs
http://dsc.discovery.com/videos/crocodile-feeding-frenzy-alligator-egg-hunt.html
http://www.metacafe.com/watch/198880/weird_nature/
Class Reptilia – 4 Orders
• Order:
Rhynchocephalia
– Tuataras
• 2 species!!
• New Zealand
Class Reptilia – 4 Orders
• Order: Squamata
– SO: Lacertilia
• Lizards
• 4 limbs and tail
– SO: Serpentes
• Snakes
• Limbless
– SO: Amphisbaenia
• Amphisbaenians
• Short tails
• Scales in rings
• Limbless
• Subterranean
http://www.youtube.com/watch?v=Unzg7C1KJo0
http://www.youtube.com/watch?v=rwRdqkEcmbs