BIS2C_Lect27_Ward_Cnidaria_ppt

BIS2C_Lect27_Ward_Cnidaria_ppt - BIS2C Winter 2012 (Ward)...

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1 BIS2C Winter 2012 (Ward) Lecture 27. Cnidaria Today’s lecture (2 March) Eumetazoa Cnidaria characteristic features biology within-group diversity Monday’s lecture (5 March) introduction to Bilateria blastula ? diploblasty gastrula triploblasty Clicker Question 1. Given that the clade Eumetazoa comprises all animals except sponges and placozoans, which of the following traits are not ancestral conditions of Eumetazoa? a. Gastrulation b. Formation of blastula c. Diploblastic construction d. Triploblastic construction e. a and d blastula ? diploblasty gastrula triploblasty Synapomorphies of Eumetazoa (or Eumetazoa + Placozoa) gastrulation: formation of gut for extracellular digestion diploblasty (later modified to triploblasty) 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 : 1435–1443. Clicker Question 2. What changes in animal feeding habits were likely brought What changes in animal feeding habits were likely brought about by the origin of the Eumetazoa (~650 mya)? a. Increased consumption of aquatic embryophytes b. Increase in size of food items consumed c. Decreased consumption of marine eukaryotes d. Increased levels of filter-feeding
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2 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… Recent genomic studies (e.g., Philippe et al., 2009, Current Biology 19 : 706- 712) support 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
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3 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
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BIS2C_Lect27_Ward_Cnidaria_ppt - BIS2C Winter 2012 (Ward)...

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