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24 Cards in this Set
- Front
- Back
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cnidaria is named after...
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cnidocytes, that have the stinging organelles nematocysts ONLY in this phyla
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special about cnidarians as metazoans
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longest fossil history
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habitat
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shallow marine, some freshwater. warm temperatures, tropical regions, never terrestrial
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examples of the phyla
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hyroids, sea anemones, jellyfishes, corals
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their movement
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sessile, slow, but prey upon swifter animals
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in what depth of water must algae reside?
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shallow, the algae are photosynthetic
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dimorphism and polymorphism
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two types
all members of a group specialized for a function |
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medusa
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-jellyfish form adapted for a floating, free swimming existence
-tetramerous symmetry -mouth on concave side -large mesoglea |
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polyps-
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hydroid forms adapted to sedentary or sessile lifestyle
may live singly or in colonies |
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examples of polyps
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sea anemones and corals (not dimorphic)
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benefit of dimorphism
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feeding and distribution possibilities of both pelagic (open water) and benthic environments
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nematocysts
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-stinging organelles, 20 types
-tiny capsules composed of chitinous-like w coiled thread |
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operculum
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the lid of the nematocysts
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development of nematocysts
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-produced by cnidocyte, the cell that encloses it
-the triggerlike cnidocil is a modified cilium |
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cnidaria compared to sponges in terms of complexity
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more highly organized, but still simple
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what causes nematocyst discharge
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-due to tensional forces generated during nematocyst formation and high osmotic pressure in nematocyst
-high internal pressure makes water go in capsule...operculum opens and pressure forces thread out |
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nerve net
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diffuse nervous system
nerve cells at base of epidermis and base of gastrodermis no myelin two way NT transmission no CNS, info from various directions |
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how is nerve net an evolution landmark
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its still in the human digestive system doing peristalsis
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symmetry
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radial, approach environment from all sides. body parts as arranged concentrically
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level of organization
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tissue...some organs
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germ layers
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ectoderm-epidermis
mmesoglea-sometimes mesoderm endoderm-gastrodermis |
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internal body cavity
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gastrovascular cavity, lined w gastrodermis (mouth and anus in one)
extracell digestion in g cav, intra in gastrodermis |
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tentacles
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aid in food capture
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sense organs
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radiates as simplest possessors
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