phylum nematoda (chapter 27.2)
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Phylum Nematoda (Chapter 27.2). Please set up your notebook for Cornell Notes. Nematodes Characteristics Slender, unsegmented w/ tapered ends Range from microscopic to 1 meter long Most are free-living, some are parasitic Develop from three germ layers - PowerPoint PPT PresentationTRANSCRIPT
Phylum Nematoda (Chapter 27.2)Please set up your notebook for Cornell Notes
NematodesCharacteristics
Slender, unsegmented w/ tapered endsRange from microscopic to 1 meter longMost are free-living, some are parasiticDevelop from three germ layers
Have a body cavity b/w endoderm and mesoderm
PseudocoelomateHave a digestive tract with two openings
Form and functionFeeding
Free living worms are predators with grasping mouth partsSoil dwelling and aquatic forms eat algae, fungi or decaying organic matter
Respiration, Circulation and ExcretionThese processes take place by diffusion
ResponseSimple nervous system with several gangliaNumerous sense organs
MovementNematodes have muscles that extend the length of the bodyUse the pseudocoelom and a hydrostatic skeleton
ReproductionSeparate male and female organismsReproduce sexually using internal fertilizationParasitic roundworms have life cycles that involve two or three host or multiple organs in one host
Roundworms and Human DiseaseTrichinosis caused by Trichinella
Mate in intestines of host, larva are released into the blood stream to take up residence in various organs, become inactive cysts in muscles cellsExtremely painfulCommon hosts are pigs and rats
Human contract by eating undercooked, infected pork
Filarial worms threadlike worms that live in blood and lymph vessels of birds and mammals
Transmitted by biting insectsCause elephantitis extreme swelling due to buildup of fluid
Ascarid wormsAscaris lumbricoides
Mature in intestine and release eggs in fecesFeces can contaminate food or water continuing cycleCauses malnutrition
Hookworms soil dwellingLay eggs in soilPierce feet to burrow into skin and enter blood streamConsume blood causing weakness and poor growth
Pinworms most common parasitic infection in US
Adults live in large intestineMigrate to anal region to lay eggsResults in intense itching that spreads eggs to clothes and bedding