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11 Cards in this Set
- Front
- Back
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Main evolutionary milestones
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-complete digestive tract (mouth-anus) allows for specialization of digestive organs
-separate mouth + anus - separate sexes -pseudocoelomate (body cavity) |
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Body plan
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-unsegemented
-usually cylindrical, round, smooth, tube like w/ pointed ends -two body openings -most free-living, some parasitic -cephalization |
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Similarities to platyhelminthesis
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-bilateral sym
-3 tissue layers -tegument + cuticle (protection) |
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Differences to platyhelminthesis
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- complete digestive tract
-pseudocoelom (false cavity) filled w/ fluid b/w mesoderm + gut -separate` sexes |
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Reproduction
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-separate sexes in most
-Female: long pair of thin, coiled ovaries: produce 1000s of eggs each day - Male: has one testicle that produces sperm -internal fertilization -shell glands secrete 'shells' around fertilized eggs |
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Locomotion
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-longitudinal muscles contract pulling head/tail close together like a whip
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Digestive system
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complete with seperate mouth + anus, so food only moves in 1 direction
-food digested, nutrients absorbed, + undigested remains move through tract to be eliminated out of anus |
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Circulation + Respiration
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-no organ systems
-breathe + excrete through moist skin -fluid in pseudocoelom transfers digested foods + dissolved oxygen |
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Evolutionary advances over Platyhelminthesis
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-complete gut: more efficient digestion
-dioecious (seperate sexes): ONLY sexual reprod = greater genetic diversity as they have to find more different mates -Pseudocoelom: Area contains internal organs + helps distribute materials, also forms hydarulic skeleton to push muscles against, gives round shape |
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Complete gut
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two openings (mouth/anus)
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Ecological roles
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-Free living: decomposers in soil, digest dead matter + return useful material to soil, 3 billion in acre of topsoil
-Parasitic: harmful + harmless. Harmful: can cause millions $ crop loss every year, hookworm + trichnia worm (trichnosis) |
