Bio 201 F08 True lect 15v4r

Bio 201 F08 True lect 15v4r - Review from last time Sea...

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Unformatted text preview: Review from last time Sea cucumbers have evolved a form of bilateral symmetry in their adult form Elongation of oral-aboral axis Typically position themselves on sea bottom, with a dorsal side (up) and ventral side (down) Ventral side has tube feet http://www.coral-reefs.org/assets/images/seacucumber(1).jpg LIFE 8e Fig. 33.1 Deuterostomes Echinoderms Urochordates called tunicates or sea squirts Cephalochordates (lancelets) Vertebrates notochord 1. Cranium (skull) 2. Brain elaboration 3. Paired sense organs on head 4. Neural crest cells Hemichordates acorn worms Formally NOT chordates Hemichordates Acorn worms Marine, worm-like deuterostomes a Phylum of Deuterostomes (only brieFy mentioned textbook) Have some similarities to both echinoderms and chordates Tornaria larvae very similar to sea star larvae Have gill slits and dorsal nerve cord similar to chordates Do not have a notochord echinoderms hemichordates chordates Phylum Hemichordata Acorn worms and Pterobranchs 3 Body regions Each with Coelomic space Proboscis Collar Trunk Enteropneusts = Acorn Worms free living Hemichordates ~75 known species Up to 2m in length Class Enteropneusta Pharynx Gill Slits - may be homologous to chordate gill slits U-Shaped Collect Food - primary function Also function in respiration http://gecko.gc.maricopa.edu/~lsola/bio18 2/labreview/embryo/bipinn.jpg Similarity of hemichordate Tornaria larva to sea star Bipinnaria larva http://scaa.usask.ca/gallery/lacalli/images/tornaria3.jpg Pterobranchs Sedentary tube- dwellers-secrete rigid tubes-colonial-most species: no dorsal nerve cord and only one gill slit Class Pterobranchia ~20 known species All very small (<12mm) Collar tentacles capture small prey and perform gas exchange Some species are colonial Invertebrate chordates Echinoderms Urochordates called tunicates or sea squirts...
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This note was uploaded on 04/14/2009 for the course BIO 201 taught by Professor True during the Fall '08 term at SUNY Stony Brook.

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Bio 201 F08 True lect 15v4r - Review from last time Sea...

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