BSC 116 Lecture Notes - Lecture 12: Tetrapod, Placodermi, Chondrichthyes
24 Feb 2017
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Vertebrates and certain invertebrates are united in the deuterostomia: traditionaly, deuterostomia included all the taxa with deuterostome development. Echinoderms, chordates, lophophorates: modern deuterostomia has two phyla: Vertebrates (fish, frogs, chickens, apes) and related invertebrates. penta-radial symmetry: biradial larvae: unique water vascular system with tube feet, no organs for water balance: exclusively marine, asexual (regeneration) and sexual (broadcast spawning) reproduction, six classes: Class echinoidea: sea urchins and sand dollare. Class crinoidea: sea lillies and feather stars. All chordates share four unique traits (at least at some point: notochord- long, flexible rod of cells. My be replaced by other skeletal elements. Something for muscles to pull against for swimming: hollow, dorsal nerve cord. Otherwise, usually solid and ventral: pharyngeal slits. Water enters mouth passes through slits: suspension feeding. In more derived chordates, modified into gills, jaws, etc: post-anal tail. There are 3 chordate clades that lack vertebrae: lancets (cephalochordata)
