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Phylum Annelida { Segmented Worms { What are the two other phyla of worms that we just learned, one was on your test? Unit 7 Worms 3 Slide Recap! { Platyhelminthes Recap! Flat worms (12,000 species) Things you should know: o What kind of symmetry? o What was the term for having a defined head? o How many layers of tissues, and what are they? Things you might know: o They are typically flattened dorso-ventrally (thin from front to back). o They sometimes contain a gut o They are acoelomate (no body cavity). o They have distinct organs and organ systems (e.g., digestive, nervous, reproductive, etc. o They DO NOT have a circulatory system! o It has the following classes: cestoda (tape worms), trematoda (flukes), monogea (flukes), turbellaria (planarians) { Nematoda Recap! Round worms (90,000 described species, though probably many more exist) Things you should/might know: o What would the cross section of this worm look like? o They differ from Flatworms in regards to body cavity how? o They do not have cilia, but have a thick cuticle. Together with pseudocoelom (which o provides a hydrostatic skeleton) provides a skeleton for the worm. o They have a complete digestive tract. (mouth -> anus) o They only have longitudinal muscles. Therefore move by “thrashing” or “whipping” around o Still they DO NOT have a circulatory system { o o o There are about 12,000 species an old theory says they gave rise to the arthropods. More recent information seems to contradict this, though. earthworms and leeches probably best known examples. Segmented WormsPhylum Annelida Major Characteristics! o o { o o o o o o They have a true coelom, though partitioned by septa (septa are incomplete in polychaetes). They have a digestive tract, blood vessels, nerve cords run the length of the animal They have “heart” (actually pumping blood vessels) and blood vessels present (earthworms respire through skin-closed system), SO THEY DO HAVE A CIRCULATORY SYSTEM They have metanephridia (a primitive kidney) They also brain-like ganglia (biological tissue) They are hermaphroditic, but cross fertilize (clitellum is reproductive organ). They have a variety of muscles circular, longitudinal, others. They have a hydrostatic skeleton (coelom+muscles) Phylum Annelida has 3 classes: o { o o Polychaetes Oligochaeta Hirudinea o { o o o o They contain parapodia - “pair” of lobes (paddles) with setae (stiff hair like projections used for traction) that help worm move. These parapodia are also vascularized (i.e., supplied with lots of blood vessels) for respiration. Contain no permanent gonads. They feed in many different ways Mostly marine. Polychaetes Earthworms: { Oligochaeta o They live in soil and fresh water. o They only have a few setae per segment, and no parapodia (un-jointed lateral outgrowths that bear the chaetae) o The clitellum (glandular, nonsegmented section near the head) is used for mating (line up and transfer sperm across clitellum). o They feed on soil nutrients and decaying vegetation. Important in keeping soil aerated. Leeches: o { o o o o o Hirudinea They have no setae They still have a clitellum They have suckers front and back (for locomotion) They have raptorial or parasitic (have anticoagulant in saliva) They are not very segmented internally - lots of connective tissues instead. some are again being used in medicine to help alleviate tissue swelling (anti-coagulants). Now for a quick activity… Please make it so that your table has exactly 3 people { { You will be given three worm cookies in cups, when I say go you are to place the worm cookies in their correct phyla. The cookies should be ordered from left to right in the following order: Platyhelminthes/Nematoda/Annelida The winning group will get a Free HW pass (Which cannot be used on any part of the Research Project) Now since we are worm experts…