lecture_11_17_1_Bilaterians

lecture_11_17_1_Bilaterians - Triploblastic condition...

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Bilaterian metazoans - Features - Two major clades
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Features that tend to evolve with bilateral symmetry: -Cephalization -Triploblasty -Increased sensory ability -Increased locomotor ability -Organ systems, increased body complexity
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Evolution of bilateral symmetry-- Advantages?
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Hox genes? No symmetry, 1 cell layer Motile Multicellular Heterotroph
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Two fundamental clades: Protostomes = “mouth first” Deuterostomes = “mouth second” Protostomes: most diverse Deuterostomes: less diverse
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Totals: Sponges: ~8000 species Diploblasts: ~11,000 Bilaterians Protostomes: ~1,325,000 Deuterostomes: ~60,000 Bilaterian total: ~1,400,000
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Unformatted text preview: Triploblastic condition, including a generalized coelom Becomes mouth Becomes anus Becomes mouth A real embryo Protostomes Becomes anus Becomes mouth Becomes anus A real embryo Deuterostomes Cleavage patterns Protostomes: spiral cleavage Deuterostomes: radial cleavage Note: no ideas on why one may be superior to the other What do you think is the most meaningful measure of evolutionary success? A) The number of living species in a lineage (insects) B) The evolutionary longevity of a lineage (bacteria, cnidarians) C) The ecological dominance of a lineage (vertebrates)...
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This document was uploaded on 03/07/2010.

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lecture_11_17_1_Bilaterians - Triploblastic condition...

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