PNB 2250 Lecture Notes - Lecture 2: Agnatha, Symmetry In Biology, Placodermi
31 Aug 2016
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Two layers of cells surrounding the jelly-like interior. Unique type of neuron not seen in other animals. Fossils for ctenophores are 515 million years old. Chordates: notochord, pharyngeal slits, doral neural tube, endo style, bilateral symmetry and tail, vertebrates (mammals, fish, reptiles, amphibians, birds, tunicate (sea squirts, lancelets) Hagfish: agnatha- very old jawless fish, fresh and marine, 4-500 million years old. Jawed vertebrates: 60,000 species, 99% of all living vertebrates, teeth, jaws, chondrichythes- cartilaginous fish, placodermi- extinct armored fish, teleostemi- bony fish. Chondrichthyes: sharks, rays, skates, cartilaginous skeleton. Reptiles: turtles, crocodiles, snakes, lizards, 312 million years old, oviparous and viviparous (lay eggs and give live birth, reptile eggs surrounded by membranes for protection and transport. Birds: feathers, beak, no teeth, hard-shelled eggs, high metabolic rate, four-chambered heart, lightweight by strong skeleton, 2-9 feet in size, birds are surviving dinosaurs, pterosaurs are largest animal to ever fly.
