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FLATWORMS

FLATWORMS. Belong to the KINDGOM ANIMALIA PHYLUM PLATYHELMINTHES. Characteristics. Three germ layers (endoderm, ectoderm, mesoderm) Bilateral symmetry Cephalization (has a head) COELOM = fluid filled body cavity Acoelomates = without coelom. FORM AND FUNCTION. FEEDING

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FLATWORMS

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  1. FLATWORMS Belong to the KINDGOM ANIMALIA PHYLUM PLATYHELMINTHES

  2. Characteristics • Three germ layers (endoderm, ectoderm, mesoderm) • Bilateral symmetry • Cephalization (has a head) COELOM = fluid filled body cavityAcoelomates = without coelom

  3. FORM AND FUNCTION FEEDING 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

  4. Respiration, Circulation, and Excretion • Thin bodies allow for materials to diffuse (respiration, excretion, etc) • Flame Cell – specialized cells that remove excess water

  5. Response Ganglia – group of nerve cells that control the body (like a brain) Eyespot – group of cells that can detect light (like an eye)

  6. Movement Flatworms move in 2 ways • Cilia helps them glide through the water • Muscle cells help them twist and turn

  7. Reproduction Sexual Reproduction – most flatworms are hermaphrodites (have both male and female sex organs) Asexual Reproduction by fission – flatworms can split in two and regenerate

  8. Groups of Flatworms CLASS TURBELLARIA - free living flatworms - live in fresh or marine water - ex. Planarian

  9. Dugesia lives in freshwater, mostly a scavenger but can also feed on protists

  10. Planarians are hermaphrodites They can also regenerate body parts and will sometimes split in half to reproduce (FISSION)

  11. ANATOMY OF A PLANARIAN

  12. Brain (ganglia) - planarian can process information about their environment Pharynx - used for suckling food in (the mouth is at the end of the pharynx) Eyespot - simple eye, can detect light Flame cells - located along the lateral edges, used for excretion Intestine - digestion (does not have an anus)

  13. 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

  14. 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.

  15. Class Cestoda =tapeworms Long, flat, parasitic Live in intestines

  16. Scolex = a structure that contains suckers and/or hooks Proglottids = body segments of the tapeworm

  17. Each mature proglottid is a hermaphrodite Testes produce sperm, fertilize the eggs to produce a zygote Zygotes are passed out through the feces.

  18. Sometimes, a dormant, protective cyst is formed in the intermediate host muscles ****This is why you should never eat incompletely cooked meat.

  19. Adapted from www.thebiologycorner.com

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