invertebrates 3 nematoda and annelida. phylum nematoda: the roundworms
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Invertebrates 3Invertebrates 3
Nematoda and AnnelidaNematoda and Annelida
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Phylum Nematoda:Phylum Nematoda:The roundwormsThe roundworms
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Evolutionary relationshipsEvolutionary relationships
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Nematode body cavity: Nematode body cavity: pseudocoelompseudocoelom
Mesoderm on inside of body wall, but not Mesoderm on inside of body wall, but not surrounding gutsurrounding gut
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Body planBody plan Feeding/digestive systemFeeding/digestive system
Nematodes suck!Nematodes suck! Complete digestive systemComplete digestive system
Gas exchangeGas exchange Body surfaceBody surface Intestinal surface (minimal)Intestinal surface (minimal) Body cavity (pseudocoelom)Body cavity (pseudocoelom) No circulatory systemNo circulatory system
Excretory system/osmotic regulationExcretory system/osmotic regulation Exists, not well-understood Exists, not well-understood
Locomotion:Locomotion: Have only longitudinal muscles Have only longitudinal muscles
Demo: The nematode swim!Demo: The nematode swim!
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Body plan (cont.)Body plan (cont.)
Nervous systemNervous system ““Brain”: nerve ring Brain”: nerve ring Four nerve cords (where?)Four nerve cords (where?) Ganglia along ventral cordGanglia along ventral cord Unique connection of muscles and nervesUnique connection of muscles and nerves Sensory structuresSensory structures
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Reproduction, etc…Reproduction, etc…
ReproductionReproduction Sexes usually separate, but some hermaphroditesSexes usually separate, but some hermaphrodites Internal fertilizationInternal fertilization
Many parasitic formsMany parasitic forms Trichina wormsTrichina worms HeartwormsHeartworms River blindnessRiver blindness ElephantiasisElephantiasis Also parasitic in plantsAlso parasitic in plants
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Phylum Annelida:Phylum Annelida:The segmented wormsThe segmented worms
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Evolutionary relationshipsEvolutionary relationships
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Aceolomates, Pseudocoelomates Aceolomates, Pseudocoelomates and Coelomatesand Coelomates
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PseudocoelomPseudocoelom CoelomCoelom
Surface area for Surface area for nutrient absorption nutrient absorption and gas exchange and gas exchange
++ ++
Larger organsLarger organs ++ ++
Fluid cushions/ Fluid cushions/ protects organsprotects organs
++ ++
Hydrostatic skeleton Hydrostatic skeleton is possibleis possible
++ ++
Completely lined by Completely lined by mesoderm mesoderm
-- ++
Mesenteries suspend Mesenteries suspend internal organsinternal organs
-- ++
Independent Independent movement of gutmovement of gut
-- ++
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Basic Annelida featuresBasic Annelida features
Have all features of protostomes Have all features of protostomes (know!)(know!)
Have body segmentation (new feature)Have body segmentation (new feature) Repetition of body partsRepetition of body parts Similar structures found in each regionSimilar structures found in each region Some specialization of regionsSome specialization of regions Some continuous parts (digestive system)Some continuous parts (digestive system)
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Annelid diversityAnnelid diversity
Class Polychaeta
Class Oligochaeta
Class Hirudinea
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Body Plan (earthworm)Body Plan (earthworm) Digestive systemDigestive system
CompleteComplete Specialized regionsSpecialized regions
CirculationCirculation Closed systemClosed system Multiple heartsMultiple hearts
Gas exchangeGas exchange Body surfaceBody surface CoelomCoelom Parapodia Parapodia
(Polychaetes)(Polychaetes) ExcretoryExcretory
MetanephridiaMetanephridia
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Body Plan (cont.)Body Plan (cont.) Nervous systemNervous system
Brain (=cerebral Brain (=cerebral ganglia)ganglia)
Ventral nerve cord Ventral nerve cord (fused pair of cords)(fused pair of cords)
One ganglion per One ganglion per segmentsegment
MovementMovement PeristalsisPeristalsis SetaeSetae
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Feeding in different classesFeeding in different classes Class Oligochaeta: EarthwormsClass Oligochaeta: Earthworms
Earth suckers (create vacuum by expanding muscular pharnyx)
Why important in ecosystem? Class Polychaeta: Marine segmented wormsClass Polychaeta: Marine segmented worms
Many are tentacle feeders Many other feeding modes
Class Hirudinea: LeechesClass Hirudinea: Leeches Food suckers (create vacuum by expanding pharynx,
digestive tract) How do blood sucking leeches feed?. What three substances do blood sucking leeches
secrete to aid in the process? NOTE: Not all leeches are blood suckers!