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Phylum Annelida (Chapter 27.3)

Phylum Annelida (Chapter 27.3). Please set up your notebook for Cornell Notes. Annelids Characteristics Body divided into segments separated by walls called septa Have a coelom  coelomates Some worms have bristles called setae attached to each segment

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Phylum Annelida (Chapter 27.3)

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  1. Phylum Annelida (Chapter 27.3) Please set up your notebook for Cornell Notes

  2. Annelids • Characteristics • Body divided into segments separated by walls called septa • Have a coelom  coelomates • Some worms have bristles called setae attached to each segment • Have mouth and anus, digestive tract • Triploblastic  three germ layers

  3. Form and Function • Feeding and digestion • Filter feeders, predators, decomposers • Have a pharynx • Pharynx has jaws in carnivores • Pharynx covered in sticky mucus in decomposers • Pharynx pumps food and soil into esophagus • Crop – stores food • Gizzard – grinds food into smaller pieces • Food absorbed in intestines

  4. Circulation • Annelids have a closed circulatory systems • Two major blood vessels • No heart – dorsal blood vessel contract and circulates blood • Respiration • Aquatic annelids breathe using gills feathery structures used to exchange gases underwater • Land dwelling annelids diffuse gases through moist skin

  5. Excretion • Digestive waste passes out of the anus • Nitrogenous waste is excreted through the nephridia organs that filter fluid in coelom • Response • Most annelids have a brain and several nerve cords • Marine annelids have many sensory adaptations • Sensory tentacles, chemical receptors, statocysts, eyes

  6. Movement • Two major groups of muscles • Longitudinal  contract to make the worm shorter and fatter • Circular  contract to make worm longer and thinner • Marine annelids have paddle-like appendages called parapodia on each segment used for swimming and crawling

  7. Reproduction • Most annelids reproduce sexually • Some have separate sexes, and external fertilization • Others are hermaphroditic but do not fertilize their own eggs • Two worms attach to each other, exchange sperm and store for later • When eggs are ready, the clitellum secretes a thick mucus ring where eggs and sperm are deposited • Ring slips off and provides a cocoon for developing larva • Some annelids reproduce asexually through budding

  8. Classes of annelids • Class Oligochaeta • Stream-lined bodies with very few setae • Mostly live in soil and fresh water • Earthworms and tubifex worms

  9. Class Hirudinea • External parasites that suck blood and body fluids • Leeches • Live in moist habitats in tropical countries • Have powerful suckers at both ends • Posterior  attachment • Anterior  Eating

  10. Class Polychaeta • Marine annelids w/ paired, paddle-like appendages that have setae on the tip • Sandworms, blood worms • Live in cracks in coral reefs, in sand and mud and open water

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