BIOL 211 Lecture Notes - Lecture 7: Cephalization, Chondrichthyes, Platypus
Document Summary
Second opening in the gastrula becomes the mouth. This developmental similarity between echinoderms and chordates is supported by dna sequence data. Phylum echinodermata (gk: echin = spiny; derma = skin) 5 classes: sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers. A thin skin covers an endoskeleton of hard calcareous plates. Echinoderms considered to be bilaterally symmetrical because their larvae are bilateral. Some species are commercially harvested for human food. Moves its tube feet by its water vascular system. Muscle and nervous tissue, but no cephalization in adults. Everts stomach into the bivalve to digest it inside its own shell. Keystone species plays a unique role in the way ecosystems function greater than what their biomass would suggest. Sea stars eat shell fish (urchins, mussels, etc) that most others do not eat. If sea urchins and/or mussels (herbivores) take over, there wouldn"t be kelp/things they eat. Feed on the living cnidarians that produce coral reefs.
