Mollusks
Chapter 10 Section 1

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
 Bilateral
symmetry
 Digestive system, 2 openings
 Internal organs located in one
area
Mollusk: Body Structure
Body Structures
 Open
circulatory system
Blood is not inside blood
vessels
Blood sloshes over the
organs and returns
eventually to the heart
Mollusks: Circulatory System
 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
 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
 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

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.)
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
 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