Biology 3229F/G Midterm: Animal-Diversity-Midterm-Review
9 Apr 2016
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Ancestral, not derived, primitive, simplistic in design. No invertebrate or vertebrate (no common ancestor shared: humans have bilateral symmetry. Cambrian explosion is an example of adaptive radiation at the phyla level: don"t know how groups are related after the explosion and length of time. Exam: what is a cnidarian *9 characteristics that define the group: best characteristic is the cnidae complex cell in animal kingdom that harbours a harpoon like structure. Start seeing concentration of ns in active cnidarians: without head, centralized ns, discrete gas exchange, excretory or circulatory structures. Only 2 tissue layers - thin and in proximity to the environment. Allows for their size: epitheliomuscular cells formed from ectoderm and endoderm (adult epidermis and gastrodermis) Muscle tails connected to mesoglea: cnidae stinging/adhesive structures resides in a cell cnidocyte. Tentacles wrap around you and cell fires harpoon and injects neurotoxin into body thousands of injecting harpoons. Cnidocil (stinger) can be stimulated by mechanical frequencies throughout the water.
