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Bio Lab Wksht & HW Questions 96

Bio Lab Wksht & HW Questions 96 - adults with body...

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91 Class Echinoidea (sand dollars and heart or biscuit urchins). Armless echinoderms with well developed endoskeletons which may be either (1) globose with enlarged spines [sea urchins], or (2) flattened with numerous short spines [sand dollars], or (3) slightly inflated with numerous short spines [heart or biscuit urchins]. Echinoids are grazers, scraping the substrate with specialized teeth. Class Holothuroidea (sea cucumbers) Worm-like armless echinoderms with vestigial skeletons lacking spines and bodies strongly elongated along the oral-aboral axis. Note the 5 rows of tube feet. Most are suspension feeders. Phylum Chordata: Bilateral deuterostomes having (at some stage in the life cycle) a dorsal hollow nerve cord , a notochord , and paired pharyngeal (gill) slits . Most chordates also have a postanal tail . There are 3 main subphyla. Subphylum Urochordata: (tunicates or sea squirts). These are a diverse group of marine chordates with planktonic tadpole-larvae showing all four phylum characteristics, and highly modified sessile filter feeding
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Unformatted text preview: adults with body walls composed of cellulose-like tunicin, and incurrent and excurrent siphons serving an enlarged filtering pharynx. They may be found living alone or in colonies. What chordate features are shared by the larvae and adults? What function does the pharynx serve? Sketch a larva and an adult in the space below; indicate the chordate characters present on your diagrams. Subphylum Cephalochordata (lancelets) Marine fish-like chordates showing an anterior oral hood overlying oral tentacles or cirri, chevron shaped (V-shaped) myotomes (muscle segments), but lacking any vertebral or cranial skeleton. Amphioxis is an example of a Cephalochordate; it is discussed below. Amphioxis is a primitive chordate that shows the four diagnostic features well, and also shows other structures that appear to be the forerunners of some typical vertebrate structures. Unlike other chordates, the notochord in Cephalochordates extends into the anterior most portion of the animal....
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