Ward_Lect27A_Cnidaria_ppt

Ward_Lect27A_Cnidaria_ppt - BIS2C Winter 2010 (Ward)...

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Unformatted text preview: BIS2C Winter 2010 (Ward) Lecture 27. Cnidaria Todays 1st lecture (26 February) Eumetazoa Cnidaria characteristic features biology within-group diversity Second lecture introduction to Bilateria Eumetazoa Major lineages of metazoans Given that the clade Eumetazoa comprises all animals except sponges, which of the following traits are apparent synapomorphies of Eumetazoa? 1. Gastrulation 2. Formation of blastula 3. Diploblastic construction 4. Diplontic life cycle 5. 1 and 3 6. 1 and 4 Major lineages of metazoans Eumetazoa gastrula diploblasty Synapomorphies of Eumetazoa gastrulation: formation of gut for extracellular digestion diploblasty (later modified to triploblasty) radial symmetry (later modified to bilateral symmetry) nervous system musculature Recent molecular studies and the fossil record suggest that Eumetazoa arose ~650 mya. Ref.: Peterson et al. (2008) Phil. Trans. R. Soc. B 363:14351443. What changes in animal feeding habits were likely brought about by the origin of the Eumetazoa (~650 mya)? 1. Increased consumption of aquatic embryophytes 2. Increase in size of food items consumed 3. Decreased consumption of marine eukaryotes 4. Increased levels of filter-feeding Eumetazoa Consequence of acquisition of gut and nervous system: macrophagy (i.e., consumption of larger food particles than possible with filter feeding). Recent molecular studies and the fossil record suggest that Eumetazoa arose ~650 mya. Consistent with observation in the fossil record of an increase in diversity and turnover of assemblages of eukaryotes at this time (Ediacaran transition). First a few words about Ctenophores First a few words about Ctenophores ? First a few words about Ctenophores ? Philippe et al. (2009. Current Biology 19 : 706- 712) study supports monophyly of Cnidaria + Ctenophores Ctenophores (comb jellies) enigmatic group of uncertain position Ctenophores (comb jellies) enigmatic group of uncertain position radial symmetry diploblastic development complete gut Major lineages of metazoans Cnidaria (sea anemones, corals, sea jellies, cube jellies, hydrozoans) radial symmetry , around a longitudinal axis with oral (open) and aboral ends Cnidaria (sea anemones, corals, sea jellies, cube jellies, hydrozoans) radial symmetry, around a longitudinal axis with oral (open) and aboral ends often with tentacles around the oral end Cnidaria (sea anemones, corals, sea jellies, cube jellies, hydrozoans) radial symmetry, around a longitudinal axis often with tentacles around the oral end incomplete gut: single opening (serving as mouth and anus) leads to gastrovascular cavity Cnidaria (sea anemones, corals, sea jellies, cube jellies,...
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Ward_Lect27A_Cnidaria_ppt - BIS2C Winter 2010 (Ward)...

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