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Annelida- the segmented worms
3 4 Phylum Annelida: “ringed worms”
5 Class Oligochaeta: earthworms
• Little cephalization • Closed Circ. System • Paired nephridia w/ circulatory association • Hermaphroditic: clitellum • Specialized digestive tract • Cutaneous respiration • No free-swimming larval stage
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Peristaltic movement
• Contracted longitudinal muscle
• Contracted circular muscle
Creepy Crawly
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External Morphology
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Internal Morphology
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Cross-Section
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Nephridia
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Class Hirudinea: leeches • Mainly freshwater, flattened segmented worms • Parasitic, scavengers, predatory • Lack coelomic compartments • Reproduction is similar to earthworms • Secrete anesthetic and anticoagulant • Medically significant
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Medical Leeches
• 1500s B.C.!
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The trochophore larva!
2nd larval stage-Veliger larva of snail
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Annelid development
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Requirements for Animal Life • The demands of 3 unique environments
– Marine, freshwater, terrestrial • Gas exchange • Nutrition • Distribution and transport • Disposal of cellular wastes • Internal water and salt balance • Reproduction and development • Support and movement
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