BIO 2135 Chapter Notes - Chapter DigiDiv: Annelid, Hydrostatic Skeleton, Cephalopod
24 Feb 2017
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Adaptive radiation: ancestor evolution of a variety of different species from a single common. Molluscs share a distinct set of characteristics that have been modified in a number of ways. Shell (3 layers: outer periostracum, middle prismatic, inner nacreous layer) Ancient molluscs have only the mantle and spicules. Cephalopods have a reduced or lost shell, predatory and more agile. 2 body parts = visceral mass houses internal organs, muscular foot holds visceral mass. Ctenidia: has cilia on its surface, pumps water through the mantle cavity. Ciliary sorting fields in the stomach send food particles to digestive gland for scrapes organic matter from the substrate. Scrapings are trapped in mucus and pass through the mouth, to stomach final intracellular digestion winds the mucus string into the stomach. Pair of metanephridia, have nephrostomes that open into the pericardial cavity they filter metabolic waste. Don"t have shells; they are protected by spicules that are embedded in the mantle.
