EXAM 4 - E XAM 4 The Lophotrochozoans Bilaterally...

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EXAM 4 The Lophotrochozoans Bilaterally symmetrical, triploblastic, invertebrate animals Fig. 32.11 Lophotrochozoan phyla that we’re considering: Platyhelminthes Rotifer Ectoprocta Mollusca Annelia Diverse group there are 18 phyla Phylum platyhelminthes About 20,000 Live in marine, freshwater, and damp terrestrial habitats Many parasitic species Range in size from microscopic to over 20 meters long They are acoelomate animals( no fluid filled cavity between digestive cavity ) They either have incomplete digestive systems (gastrovascular cavities), or they lack digestive systems entirely In those with gastrovascular cavities, digestion is a combination of extracellular and intracellular Four classes: o Class turbellaria (planarians) o Class trematoda (flukes) o Class cestoda (tapeworms) o Class monogenia Class burbellaria Free-living flatworms, many are marine (fig. 33.9) Dugesia- a freshwater planarian-carnivores, scavengers/ cephalized-have a distinct head, move using cilia on ventral side, have eye spots, have a nerve system o Planarians are hermaphrodites o Copulation is mutual-ie each partner inseminates the other o Can also reproduce asexually-fragments can regenerate Class trematoday-flukes Parasites that attach to hosts using suckers Have gastrovascular cavities Many species have complez life cycles involving an intermediate host, in which larvae live, and final host in which the adult lives Sichistosomiasis o A human disease caused by infection with blood flukes
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o 200 million people infected worldwide, common in Egypt o Debilitating diseas (anemia, dysenteriy) o Like many parasites, they produce large numbers of offspring o Schistosoma blood flukes, in contrast to most flatworms, have separate male and femal individuals o Adults live together in a constant state of copulation (sperm is always being transferred to female) o Infects by digging through the skin Class cestoda- tapeworms Parasitic flatworms found mostly in the intestines of vertebrates- including humans Lack a digestive system- absorb materials pre-digested by the host Can be over 20 meters in length (table 33.2) Phylum rotifera About 1,800 species Mostly freshwater Smaller than many single-celled protists, but are rather complez multicellular animals Are pseudocoelomates(have a body cavity-not lined with muscle tissue) Have a complete digestive system Reproduction o Some species of rotifers consist entirely of females o New individuals are produced ffrom unfertilized (but 2N) egg’s that were produced by mitosis o Called parthenogenesis-(only female diploid eggs) Phylum ectoprocta Bryozoans or moss animals Freshwater and marine Characteristics o 4,500 species, mostly marine o Are coelomate animals o Are deuterostomes (one of the inconsistencies between the morphological and molecular phylogenies) o Have complete u-shaped digestive systems-mouth and anus on same side of the
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EXAM 4 - E XAM 4 The Lophotrochozoans Bilaterally...

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