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Download Unsegmented Worms - Biology Junction
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Unsegmented Worms Flatworms Flatworms • Belong to the phylum platyhelminthes. (Plat = flat) • There are three classes: – Turbellaria – Trematoda – Cestoda Characteristics of Flatworms • They are acoelomates (they don’t have body cavities) • They have bilateral symmetry • Show cephalization • Respiration through skin • Single opening to digestive tract (pharynx) Class Turbellaria • • • • Spade-shaped head and two eyespots Eat protozoans for scavenge Flame cells remove waste Are hermaphrodites (have male and female reproductive parts) • Can reproduce by regeneration • Are free-living Class Trematoda • Are parasitic flukes • Have suckers on both ends of the body • Can live inside or outside of host Class Trematoda • Nervous and excretory systems like turbellarians • Hermaphrodites • Have complex life cycles Fluke Life-Cycles The long and complex life-cycle of the fluke can be made easier to understand through the use of a nonsense mnemonic : Every - Egg Mirror - Miracidium (free-living in water) Spotted - Sporocyst (in snail) Red - Redia (in snail) Certainly - Cercaria (free-living in water/snail) Met - Metacercaria (in 2nd intermediate host) Approval - Adult Class Cestoda • Parasitic • Tapeworms • Long, ribbon-like bodies • Absorbs nutrients from host • Hermaphrodites Tapeworm Anatomy Roundworms Roundworms Roundworms • • • • • Belong to phylum Nematoda Pseudocoelomates (fluid filled body cavity) Slender bodies that taper on both ends Have mouth and anus Can be free-living or parasitic Pinworms live in human intestines Trichinosisa disease from eating infected pork Cysts in Contaminated Pork Rotifers • Known as rotifers or wheel animals • Transparent, free-swimming microscopic animal • Freshwater & marine • Have a ring of cilia around mouth that rotates like a wheel to bring in food • Feed on unicellular algae, bacteria, & protozoa Rotifers • Have a muscular organ called the mastax behind the pharynx to chop food • Nervous system composed of anterior ganglia & 2 long nerve cords • Show cephalization (head end) • Have 2 anterior, lightsensitive eyespots Rotifer Anatomy
