3454lablecture9 - Elaborate filter feeding mechanism...

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LECTURE 9 PHYLUM HEMICHORDATA Acorn worms – marine animals with chordate-like characteristics Differences – no postanal tail, no true notochord Similarities – Pharyngeal gill slits, dorsal and ventral hollow nerve cord Share characteristics Echinodermata in larval stages, Dipleura larval stage is very similar to Tornaria in Hemichordates Deuterostomes with enterocoely Filter feed with pharyngeal gill slits PHYLUM CHORDATA Four main characteristics: 1. postanal tail 2. pharyngeal gill slits 3. notochord 4. dorsal hollow nerve cord SUBPHYLUM UROCHORDATA Tunicates and Sea Squirts Larval stage is very similar to a tadpole with all 4 characteristics but sessile adult forms only have pharyngeal gill slits retained
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Unformatted text preview: Elaborate filter feeding mechanism detailed in lab manual Adult retains separate anus and mouth opening, hermaphroditic with external fertilization SUBPHYLUM CEPHALOCHORDATA Amphioxus, Lancelets Notochord extends into head cavity Retain all 4 characteristics as adults Filter feeders, live in bottom substrate Gonochoristic with external fertilization, no larval stage SUBPHYLUM VERTEBRATA Thought to have evolved from Cephalochordates due to major similarities with Lamprey larvae and Cephalochordates TAXONOMY CHANGES CLASS AGNATHA IS NOW KNOWN AS SUPERCLASS AGNATHA CLASS MYXINI – HAGFISH CLASS PETROMYZONTES - LAMPREY...
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This note was uploaded on 11/29/2009 for the course BIOLOGY 3454 taught by Professor Nelson during the Spring '09 term at UT Arlington.

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3454lablecture9 - Elaborate filter feeding mechanism...

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