BIO SCI 94 Lecture Notes - Lecture 16: Inside Out Music, Motility, Chordate
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BIO SCI 94 Full Course Notes
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Five major lineages of echinoderms are living today: crinoidea feather stars and sea lilies, asteroidea sea stars, ophiuroidea brittle stars and basket stars, echinoidea sea urchins and sand dollars, holothuroidea sea cucumbers. Echinoderms (cid:894)(cid:862)spi(cid:374)y-ski(cid:374)s(cid:863)(cid:895) are are (cid:373)ari(cid:374)e a(cid:374)i(cid:373)als (cid:374)a(cid:373)ed for the spi(cid:374)es or spikes observed i(cid:374) many species. Three main synapomorphies (and dna) identify the echinoderms as a monophyletic group: radial symmetry in adults. Larvae are bilaterally symmetric, as are all deuterostomes. However, adults have pentaradial symmetry (five-sided radial symmetry: endoskeleton of calcium carbonate, water vascular system. ~the water vascular system is a series of branching, fluid-filled tubes and chambers that functions as a hydrostatic skeleton. ~the endoskeleton looks like it is on the outside of the animal (and if it were, it would be an exoskeleton) but it is not - there is a tough skin on top of it.