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Segmented Worms Annelids Tube shaped worms with rings New Words • Setae- bristle-like structures • Crop- a sac used for food storage • Gizzard- a muscle that grinds up bits of soil and organic matter • Anterior- front end of an organism • Posterior –back end of an organism • Hermaphrodites- organisms that produce sperm & eggs in the same body Segmented Worms • • • • • Use setae to hold onto soil and move Have bilateral symmetry Body cavity that holds organs Two body openings (mouth & anus) Annelids are found in freshwater, saltwater & moist soil Earthworm Body Systems • Have a definite anterior- front end • Have a definite posterior- back end • Each body segment (except the first and last) have a pair of setae & 2 sets of muscles Earthworms burrow through soil • They take soil into their mouth They get energy from soil & other organic matter found in the soil • The soil moves to the crop and into the gizzard to be ground, broken down, and the nutrients absorbed my the blood Waste leave the worm through the anus Clitellum A thick ring structure used in reproduction When earthworms take in soil, they provide spaces for air and water to flow through it and mix the soil Their wastes pile up a the openings to their burrows • We call these wastes “castings” • The castings help fertilize the soil Vermicompost We call these casting VERMICOMPOST • They are used as an organic fertilizer in gardens Earthworms have a closed circulatory system Two blood vessels run from the top to the bottom of their bodies • They have a heartlike structure called “aortic arches” which pump blood to the body Oxygen and carbon dioxide are exchanged through their skin • They DO NOT have gills or lungs! • You can suffocate an earthworm by touching it with dry hands or by wiping off their mucous layer • However – they cannot survive submerged in puddles of water either • It is a delicate balance Earthworms have a small brain in their front segment of their body • Nerves in each segment form a main nerve cord that connects to the brain Earthworms respond • To light • Temperature • moisture Earthworms are Hermaphrodites • They have body male and female reproductive structures in one body • One individual CANNOT fertilize its own eggs • It must receive sperm from another earthworm in order to reproduce Earthworms mating Why would earthworms be healthy to have in a garden or compost pile? Are you ready to dissect?
