BIO 200 Lecture Notes - Lecture 20: Notochord, Sea Urchin, Symmetry In Biology
12 Nov 2017
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Document Summary
Echinoderms & hemichordates: the deuterostome tree (development of mouth) reverse of protostomes. Ancestral deuterostomes have traits we see in modern echinoderms and chordates: Internal skeletons thin covering of skin -> neurosensory cells. Have a water vasculature system and tube feet. Madreporite water flows in ring canal and radiates into feet -> feet used for food + suction and standing on ground. Can regenerate lost limb limb may attach to another organism -> break in half and regenerate. 3 extant: crinoids (sea lilies, feather stars) Differ in ability to move -> sea lilies are anchored -> feather stars are mobile: echinozoans (sea cucumber, sea urchin, sand dollars) Sea cucumbers look bilateral by they are just elongated: asterozoans (brittle stars) Brittle stars are nocturnal grows arms in pairs: hermichordates: Sandy/muddy: chordates vertebrates, some non-vertebrates. 4 traits: hollow nerve cord, notochord, pharyngeal (swallowing) slits/pouches, post-natal tail. Two main groups of non-vertebrae chordates: tunicate and lancelet.
