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PHYLUM PLATYHELMINTHES
FLATWORMS KINDGOM ANIMALIA PHYLUM PLATYHELMINTHES
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Characteristics Three germ layers (endoderm, ectoderm, mesoderm)
Bilateral symmetry Cephalization (has a head) COELOM = fluid filled body cavity Acoelomates = without coelom
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FORM AND FUNCTION Free-living - carnivores or scavengers; they have a digestive cavity, mouth and pharynx Parasites – feed on blood, tissues or pieces of cells from within a HOST Most do not have a complete digestive system because they absorb material directly from host
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Respiration, Circulation, and Excretion
Thin bodies allow for materials to diffuse (respiration, excretion, etc) Flame Cell – specialized cells that remove excess water
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Response Ganglia – group of nerve cells that control the body (like a brain) Eyespot – group of cells that can detect light (like an eye)
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Movement Flatworms move in 2 ways
Cilia helps them glide through the water Muscle cells help them twist and turn
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Reproduction Sexual Reproduction – most flatworms are hermaphrodites (have both male and female sex organs) Asexual Reproduction– flatworms can split in two and regenerate
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Groups of Flatworms CLASS TURBELLARIA - free living flatworms
- live in fresh or marine water - ex. Planarian
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Dugesia lives in freshwater, mostly a scavenger but can also feed on protists
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Class Trematoda = parasitic flatworms (a. k
Class Trematoda = parasitic flatworms (a.k.a “flukes” live in mouth, skin, or gills of host) Primary host = the host in which a parasite reproduces sexually Intermediate host = the host in which asexual reproduction occurs
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Schistosoma mansoni - multiple host:
Primary host = human Intermediate host = snail Causes Schistosomiasis -in humans; decays lungs liver, spleen, or intestines, occurs in tropical areas with poor sanitation/sewage.
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Class Cestoda = tapeworms
Long, flat, parasitic Live in intestines
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Scolex = a structure that contains suckers and/or hooks
Proglottids = body segments of the tapeworm
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Sometimes, a dormant, protective cyst is formed in the intermediate host muscles
****This is why you should never eat incompletely cooked meat.
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