27_Ward_Cnidaria_Outline

27_Ward_Cnidaria_Outline - BIS2C W2011 Eumetazoa and...

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BIS2C W2011 Lecture 27 (23 February 2011) 1 Eumetazoa and Cnidaria Eumetazoa Eumetazoa: all animals except sponges. Characterized by: gastrulation extracellular digestion in a gut 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. Significance of first macrophagous metazoans. Ctenophores (comb jellies) Enigmatic animals of uncertain phylogenetic position – most likely sister group of Cnidaria. Feature include: radial symmetry diploblasty complete gut (in contrast to Cnidaria) Cnidaria (hydroids, sea jellies, cube jellies, sea anemones, corals) Characteristics radial symmetry , around a longitudinal axis often with tentacles around the oral end incomplete gut: gastrovascular cavity diploblastic : two cell layers separated by gel-like mesoglea two body forms: polyp (usually sessile) and
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27_Ward_Cnidaria_Outline - BIS2C W2011 Eumetazoa and...

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