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March 05, 2013 Mollusks Objectives What are the main characteristics of mollusks? How does a shell help mollusks survive? What are the three major groups of mollusks? How do mollusks obtain food and oxygen ? March 05, 2013 What are Mollusks? "soft" ◉ invertebrates ◉ soft unsegmented bodies ◉ most have a hard outer shell & 2nd largest phylum of animals ◉ thin layer of tissue called a mantle ◉ organ called a foot ◉ first animals to develop gills ◉ bilateral symmetry March 05, 2013 Examples of Mollusks Clams Snails Mussels Limpets Slugs Octopi Cuttlefish March 05, 2013 Body Structure Muscular Foot Gills found between the mantle and body used for gas exchange and capturing food takes on different forms in different animals used for movement or grasping Mantle covers the body /internal organs secretes the hard outer shell March 05, 2013 Classification of Mollusks Classified by their foot, shell and nervous system 3 major classes of mollusks gastropods bivalves cephalopods March 05, 2013 Gastropods Largest group of mollusks Live in water or on land Can have a shell or no shell ex. snails and slugs Obtaining Food use radula, a tongue like organ with teeth, to get food Move with a broad muscular foot "foot under stomach" Tentacles on head March 05, 2013 Bivalves Mollusks with two shells held together by hinges and strong muscles oysters, mussles and clams Filter Feeders use gills to strain organisms from water mucus on gills catches food cilia sweeps it into their mouths omnivores Slow Movers larvae swim or float adults usually stay in one place (oysters and mussles) others like clams do move they use their foot to dig March 05, 2013 link- Cephalopods Ocean dwelling mollusk whose foot is adapted to form tentacles around its mouth octopus, squid, cuttlefish, nautilus External, internal or no shell at all nautiluses have an external shell squids and cuttlefish have a small internal shell octopuses have no shells Obtaining Food muscular tentacles to capture prey beak crushes prey radula cuts and scrapes away the flesh Nervous System most complex nervous system of any invertebrate large brains and considered intelligent can learn and remember/ great escape artists well developed eyes for hunting Movement jet propulsion squeeze water out of mantle through tube March 05, 2013 March 05, 2013
