Biology 3229F/G Lecture Notes - Lecture 9: Recapitulation Theory, Water Vascular System, Crinoid
10 Dec 2016
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Echinos = spiny derma = skin because they have calcified skeleton similar to sea water: mutable connective tissue. Asteroidea (sea stars), echinoidea (sea urchins), crinoidea (sea lilies), ophiuroidea (brittle stars), holothuroidea (sea cucumbers) Echinoderms on far right of the tree a very derived group. Closely related to chordates echinoderms aren"t chordates. All marine/brackish water no freshwater echinoderms, all salt water. Type of skeleton make for a good fossil species; come up readily in fossil record. Adult: pentaradial 5 axes of symmetry *few exceptions. In the larval stage, the larvae are bilaterally symmetric distinct mouth and anus. Ontogeny recapitulates phylogeny development of an organism (ontogeny) Water-vascular system series of connected tubes it uses to move or feed. Locomotion using wvs using innervation (motor neurons), ampullar muscles pumped back into ampulla) manipulate the pressure within the system allowing it but they do only have bilateral symmetry.
