November 8-ch24 - November 8, 2007 Chapter 24 The Phylum...

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November 8, 2007 Chapter 24 The Phylum Cordata 4 important features o Notochord o Dorsal, hollow nerve cord o Pharyngeal gill slits o Post-anal tail Notochord o Stiff but flexible rod extending the length of the body o Between digestive tract and nerve cord o Support o Muscle attachment o In many chordates present only during early stages of development Disappears as skeleton develops o Dorsal nerve cord Runs above digestive tract, lengthwise along dorsal portion of body During development, thickens and expands anteriorly to form brain o Pharyngeal gill slits Located in pharynx Many develop into functional openings Gills o Post anal tail Notochord and nerve chord extend past the anus What makes humans cordates? Only one characteristics is the nerve chord Embryos exhibits all four Ontogeny reflects phylogeny Invertebrate chordates Lack a backbone Exclusively aquatic Tunicates (sea squirts) o Marine o Larvae are motile o Adults are sessile
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November 8-ch24 - November 8, 2007 Chapter 24 The Phylum...

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