Mollusca

General Characteristics Coelomates Protostomes Body cavity called coelom is completely enclosed within the mesoderm Specialized organs Ex. Stomach Soft bodies Toothed tongue called radula composed of chitin Three distinct body zones Head-foot Visceral mass Mantle

Classes Within Mollusca Bivalvia Monoplacophora Ex. Clam Ex. Neopilina http://www.manandmollusc.net/Shell_photos/monoplacophora.gif http://cas.bellarmine.edu/tietjen/AnimalDiversity/bivalvia01.gif

Gastropoda Cephalopoda Ex. Octopus Ex. Snail http://en.academic.ru/pictures/enwiki/83/Snail-WA_edit02.jpg http://chemistry.csudh.edu/faculty/jim/cozaugo4-600/octopus.jpg

Scaphopoda Polyplacophora Ex. Chiton Ex. Tusk Shell http://www.rakbankerd.com/kaset/Animal/632_1.jpg http://pt-lobos.com/images/lined_chiton_2c.jpg

Aplacophora Ex. Epimenia australis http://www.whoi.edu/science/B/aplacophora/epimenia.jpg

Body Plan Visceral mass contains digestive, excretory, and reproductive organs Locomotion primarily done with muscular foot Some have a differentiated head The mantle is comprised of folds that arise from the dorsal body wall that enclose the cavity between the folds themselves and the visceral mass Bivalve mollusks have two shells

Feeding Radula used for feeding consists of thousands of microscopic chitinous teeth Gastropods(Snails/relatives) use the radula to scrape food and then convey the food to the digestive tract. Other gastropods use a modified radula as a drill to drill through shells of oysters and other creatures. Has a closed digestive tract that goes from the mouth to the stomach to the intestine to the anus

Respiration The mantle is a heavy fold of tissue wrapped around the body of the mollusk the space between the mantle and the actual body is called the mantle cavity This cavity in some mollusks acts as a lung In other mollusks, it contains gills that capture the oxygen from the water when the water passes through the cavity

Circulation All mollusks except cephalopods have an open circulatory system which blood flows freely throughout the body The mollusk heart has there chambers: Two atria and one ventricle Cephalopods have a closed circulatory system with blood vessels that carry the blood to all parts of the body and then diffuse it

Excretion Nitrogenous wastes expelled by two tubular structures called nephridia Each has an open funnel, nephrostome, lined with cilia Coiled tubule runs from nephrostome to bladder, which connects to excretory pore Wastes are gathered by nephridia from coelom and discharged into mantle cavity Then are expelled by cavity by continuous gill pumping

Response If carnivore, it can used chemosensory structures to locate prey. Gastropods have tentacles with eyes on the end. Cephalopods have highly developed nervous systems. Brains unique among mollusks Many exhibit complex patters of behavior/high level of intelligence Very elaborate eyes, similar to vertebrate eyes

Movement Their foot is their primary mechanism of locomotion Some mollusks secrete mucus, forming a path that they glide along on their foot Cephalopods have foot which is divided into arms, also called tentacles. In some pelagic forms, mollusks that are perpetually free swimming, the foot is modified into wing-like projections or thin fins

Reproduction Has distinct male/female individuals Few bivalves/many gastropods are hermaphroditic Cross fertilization is most common Most aquatic mollusks engage in external fertilization Gastropods often have internal fertilization

Works Cited Bunje, Paul . "The Mollusca." University of California Museum of Paleontology. UCMP, 2003. Web. 19 Apr 2010. <http://www.ucmp. berkeley.edu/taxa/inverts/mollusca/mollusca. php>. "Gravysnail." Youtube. Web. 19 Apr 2010. Raven, Peter and George Johnson. Biology. 6th ed. NY: McGraw-Hill, 2002. 900-905. Print. "Phylum Mollusca: Mollusks ." The Diversity of Life. N.p., n.d. Web. 19 Apr 2010. <http:// infusion.allconet.org/webquest/PhylumMollus ca. html>.

The moment you’ve all been waiting for… THE VIDEO