Final Exam

specialized epidermis found in platyhelminthes specifically neodermata

muscles, circulatory system, other process

-blastocoel fills with cells -three germ layers

concentrating sense organs in the head region

layer that is in contact with the outside environment

layer that processes food

-made of contractile cells -develops from mesoderm -muscles in cnidaria have a separate evolutionary origin

-active, directed movement most efficient with an elongated body form with anterior, posterior, dorsal, and ventral sides

-very small -small chamber around the heart

-folds of tissue covering the viscera and mantle cavity -produces the shell in some molluscs -houses gills or lungs (gas exchange)

-some have a well developed head -radula (a ribbon like organ) -foot is used for movement (adhesion, extend hydraulically, burrow into mud/sand, fin-like for swimming)

-ribbon like organ -found in all molluscs except bivalves -muscles move the radula -used for scraping, piercing, tearing, cutting, and boring -acts as a conveyor belt to move food towards the stomach

-open circulatory system -includes heart and some blood vessels -vessels open to blood sinuses (larger open cavities) -respiration involves a gill-like organ

-open circulatory system -includes heart and some blood vessels -vessels open to blood sinuses (larger open cavities) -respiration involves a gill-like organ

-found in most bivalves and some gastropods -found in mantle cavity -ctenidia (primitive gill) -secondary gill or lungs in some gastropods

-most are marine, some freshwater and some brackish water -sedentary filter feeders -create water currents with cilia -no defined head -no radula -very little cephalization

-2 shells held together by hinge ligament -valves drawn together by adductor muscles (resting state is open shell -umbo is the oldest part of the shell -pearls are produced when an irritant enters between the shell and mantle (layers of nacre secreted around the foreign material)

-foot is in the midline -modified ctenida on either side of the foot -siphons are extensions of the mantle (incurrent and excurrent) -siphons can be used to obtain food and O2 and are an adaptation of burrowing marine bivalves

-not very mobile -larvae are mobile -scallops swim to escape from predators by creating a jet propulsion by clapping valves together

-some have modified gills to also collect food particles from water -derived from primative ctenidia (lengthened filaments) -filaments form plate like lamellae

-connected to respiration -filter feeding -particles enters the incurrent siphon -gland cells on gills release mucus to capture particles -cilia and palps direct the mucus and food to the mouth

-blood passes through nephridial tubules (kidneys) to remove waste

-controlled by three pairs of ganglia with connected nerve cords -simpler than annelids or arthropods -sense organs are reduced and poorly developed

-only sexual -fertilization is external (gametes released through excurrent siphon) -indirect development -produce free swimming trochophore larva -next is veliger stage -then spat stage -then adult