24. Evolution and Phylogenies Nov 23

Dorsal stalk attachment nodding heads bob at end of

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Unformatted text preview: era (?dorsal) Stalk - attachment “nodding heads” bob at end of stalk May be related to Cycliophora? historically confused with bryozoans - some suggest related 2 Tentacles - solid in cross section Ciliated on inner surface U-shaped gut - both mouth and anus within tentacle crown Cuticle - chitin Longitudinal muscle fibers Body compact - acoelomate? small spaces - pseudocoel, hemocoel, remnants of of blastocoel Rudimentary Nervous System Flame Cells (Protonephridia) – 1pr Dioecious or Hermaphroditic Internal fertilization Embryos brooded or Swimming Evolutionary relationships among metazoan phyla How do we determine phylogenetic relationships? How do we determine patterns of evolution? How do we resolve conflict when different information provides different answers? 3 "Big" questions of interest: Metazoa = multicellular animal life Are the metazoa monophyletic? Is the evolution of the coelom monophyletic? How do we define phyla? Shared body plans Enigmatic relationships to other groups What are the evolutionary origins of the protostomes and deuterostomes? Where do the lophophorate phyla fit? Are the arthropods monophyletic? Where did molluscs come from? Determine phylogenetic relationships? Similarities Shared derived characters - Synapomorphies Homologies Grades of Construction of Animals Unicellular Unicellular Protozoa - Lab this week Protozoa Cellular Grade - Specialization of cell types Determine homologies? Anatomy / Morphology Embryology Paleontology (e.g., Porifera) Tissue Grade - Cells organized into tissues (e.g., Cnidaria) Organ Grade - Tissues organized into organs (most phyla) Number of Tissue Layers Body Cavities: Diploblastic - 2 layers Ectoderm (outside) Endoderm (inside) Acoelomate - no body cavity Pseudocoelomate - cavity, but not completely lined with mesoderm Triploblastic - 3 layers Ectoderm (outside) Mesoderm (middle) Endoderm (inside) Coelomate - true coelom = completely lined by mesoderm = Peritoneum Coelom can form by Coelom Schizocoely - a splitting of the mesoderm Schizocoely Enterocoel...
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This note was uploaded on 01/27/2010 for the course BIO 37282 taught by Professor Padilla during the Fall '10 term at SUNY Stony Brook.

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