13. Mollusca II Oct 14

13. Mollusca II Oct 14 - Phylum Mollusca snails clams...

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1 Phylum Mollusca Phylum Mollusca 2nd largest phylum > 150,000 extant species > 50,000 fossil species 7 Extant Classes Aplacophora Aplacophora - worm-like, predators Monoplacophora Monoplacophora - resemble general moll. Polyplacophora - chitons Gastropoda Gastropoda - snails, slugs Bivalvia Bivalvia - clams, oysters, scallops Cephalopoda - squid, octopus Scaphopoda Scaphopoda - tusk shells No consensus on No consensus on phylogenetic phylogenetic relationships among relationships among molluscs molluscs . THINK about what information you would weigh in assessing weigh in assessing phylogenetic phylogenetic relationships. relationships. Wal er 1998 Phylogenetic tree depicting the relationships of Monoplacophora to other molluscs based on the combined analysis of all molecular loci Giribet G. et.al. PNAS 2006;103:7723-7728 BIG diffs between this and other trees We will come back to this when we talk about trees. Bivalvia Bivalvia clams, oysters, scallops All marine and freshwater Shell - 2 valves Live in a variety of habitats: on or in soft sediment in cobble, on rocks attached to rocks excavate into rocks excavate calcium carbonate excavate wood (“ship worms”)
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2 Body Orientation Dorsal - along hinge Ventral - towards gape Anterior - towards umbo Posterior – siphons (water flow in and out of mantle cavity) Left and Right valves Anterior Posterior Dorsal Ventral Hinge with teeth where valves meet
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13. Mollusca II Oct 14 - Phylum Mollusca snails clams...

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