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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 – – – – 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
