Mollusks Chapter 10 Section 1

Characteristics of Mollusks Clams, oysters, scallops, snails, squids Invertebrates with soft, unsegmented bodies Often protected by hard outer shell (protects soft body) Mantle: thin layer of tissue that covers internal organ, produces the hard shell Foot: adapted for crawling, digging, catching prey Characteristics of Mollusks

Mollusk: Body Structure Bilateral symmetry Digestive system, 2 openings Internal organs located in one area Mollusk: Body Structure

Body Structures

Mollusks: Circulatory System Open circulatory system Blood is not inside blood vessels Blood sloshes over the organs and returns eventually to the heart Mollusks: Circulatory System

Mollusks: Obtaining Oxygen Mollusks that live in water have gills Gills: organs that remove oxygen from the water Cilia: tiny, hairlike structures that move water over the gills Mollusks: Obtaining Oxygen

Three Major Groups of Mollusks GASTROPODS BIVALVES CEPHALOPODS Classified by… presence of shell, type of shell, type of foot, complexity of nervous system Three Major Groups of Mollusks

Snails and slugs Largest group of mollusks Live everywhere on Earth Single external shell or no shell at all GASTROPODS

GASTROPODS: Obtaining Food Herbivores Eat only plants Carnivores Animals that eat only other animals Scavengers Radula: a flexible ribbon of tiny teeth that scrapes food from a surface GASTROPODS: Obtaining Food

BIVALVES Oysters, clams, scallops, mussels Mollusks that have two shells held together by hinges and strong muscles NO RADULAS, strain tiny organisms from water with the use of their gills Omnivores: eat both plants and animals BIVALVES

Oysters and mussels attach themselves to rocks or underwater surfaces Clams can burrow the mud by changing the shape of its foot Grain of sand gets stuck between mantle and shell… PEARL! BIVALVES (cont.)

CEPHALOPODS Octopus, squids, nautilus, cuttlefish Ocean dwelling mollusk whose foot is adapted to form tentacles around its mouth Carnivores Use tentacles containing sensitive suckers to capture food Suckers receive sensations of taste as well as touch Don’t have to touch something to taste it CEPHALOPODS

CEPHALOPODS (cont.) Large eyes Excellent vision Most complex nervous system of any invertebrate Large brains, can remember things they have learned Jet propulsion CEPHALOPODS (cont.)

An Escaping Octopus