BIO 200 Lecture Notes - Lecture 20: Water Vascular System, Hemichordate, Echinoderm
7 Nov 2016
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Document Summary
All have internal skelatons, common ancestor was a deuterostome. Ancestral deuterostomes have traits we see in modern echinoderms and chordates. Are radially symmetric as adults, have 5 axes(pentaradial symmetry:symmetry in 5s or multiple of 5s) Have a water vasculature system and tube feet(used for attachment)(used for feeding, gas exchange and locomotion) There are 20 extinct classes of echinoderms, but only 3 extant groups: crinoids(sea lilies feather stars, Covered w/ spines anchored to the underlying skelaton (ball and socket joints) Sea cucumbers were added due to very tight genetic similarity. Are predatory and live in a range of marine habitats. Brittle stars have much thinner arms w/ no suckers(not used for attachment, only used for feeding) They are nocturnal & they can freely swim. What makes a chordate: hollo(cid:449) (cid:374)er(cid:448)e (cid:272)ord(cid:894)ru(cid:374)s (cid:271)e(cid:374)eath dorsal surfa(cid:272)e(cid:895, noto(cid:272)hord, phary(cid:374)geal slits/pou(cid:272)hes (cid:894)links mouth to esophagus, connects pharynx to external env, posta(cid:374)al tail.
