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Lecture_11_19_Annelida

Lecture_11_19_Annelida - Protostomes II Annelida segmented...

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Protostomes II: Annelida- segmented or bristle worms
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The Lophotrochozoans Trochophore larva
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The trochophore larva uniquely defines the clade that includes molluscs and annelids (the “MA clade”). Given that fact, how can that larva help one determine where the MA clade goes within the protostomes? A) It can’t B) It implies that all other protostomes are a clade united by the lack of a trochophore larva-- thus, it places the MA as sister to other protostomes C) It suggests that the MA clade is a recently derived clade within protostomes, since it must have taken a long time to evolve such a complex larval type
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A generalized annelid (an earthworm) segment septum circular muscle longitudinal muscle Highly metameric: repeated segments bristles
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Seta
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Using circular and longitudinal muscles to burrow Direction of movement
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Annelid diversity Polychaeta = marine worms (10,000 species) Oligochaeta = earthworms (3,000 species) Hirudinea = leeches (500 species) Phylogeny: an interesting mess!
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Parapodia are armed with setae, and are used for locomotion, anchoring, etc.
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