BIO 121 Lecture Notes - Lecture 18: Water Vascular System, Dorsal Nerve Cord, Symmetry In Biology
10 Dec 2020
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Tube feet: on oral side, hollow, muscular tubes, many end in suckers, used for locomotion, part of water0vascular system. Special compartment of coelom, contain sea water. Hydraulic of water vascular system controls tube foot movement. Water intake into system is controlled by a sieve-like structure called madreporite. Cardiac stomach: connected to mouth; is a sack that can be everted outside body to initially digest food. Food is then transferred inside the body to the pyloric stomach which continues and completes digestion. Considered internal; just under the outer surface of animal. Some ossicles are spines, which project out aboral (top_ side of animal. In sea urchins and sand dollars this is called a test. Special case of symmetry evolution: sea cucumbers. Lay on sea floor on their sides. This is essentially a form of bilateral symmetry (secondary bilateral symmetry) Have some similarities to both echinoderms and chordates. Tornaria larvae very similar to sea star larvae.
