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24 Cards in this Set

  • Front
  • Back
cnidaria is named after...
cnidocytes, that have the stinging organelles nematocysts ONLY in this phyla
special about cnidarians as metazoans
longest fossil history
shallow marine, some freshwater. warm temperatures, tropical regions, never terrestrial
examples of the phyla
hyroids, sea anemones, jellyfishes, corals
their movement
sessile, slow, but prey upon swifter animals
in what depth of water must algae reside?
shallow, the algae are photosynthetic
dimorphism and polymorphism
two types
all members of a group specialized for a function
-jellyfish form adapted for a floating, free swimming existence
-tetramerous symmetry
-mouth on concave side
-large mesoglea
hydroid forms adapted to sedentary or sessile lifestyle
may live singly or in colonies
examples of polyps
sea anemones and corals (not dimorphic)
benefit of dimorphism
feeding and distribution possibilities of both pelagic (open water) and benthic environments
-stinging organelles, 20 types
-tiny capsules composed of chitinous-like w coiled thread
the lid of the nematocysts
development of nematocysts
-produced by cnidocyte, the cell that encloses it
-the triggerlike cnidocil is a modified cilium
cnidaria compared to sponges in terms of complexity
more highly organized, but still simple
what causes nematocyst discharge
-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
nerve net
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
how is nerve net an evolution landmark
its still in the human digestive system doing peristalsis
radial, approach environment from all sides. body parts as arranged concentrically
level of organization
tissue...some organs
germ layers
mmesoglea-sometimes mesoderm
internal body cavity
gastrovascular cavity, lined w gastrodermis (mouth and anus in one)
extracell digestion in g cav, intra in gastrodermis
aid in food capture
sense organs
radiates as simplest possessors