Download 10-1 Mollusks - Saint Mary School

10-1 Mollusks
Characteristics
invertebrates with soft unsegmented bodies
that are
often protected by a hard outer shell
have a thin layer of tissue called a mantle that
covers its internal organs
a foot (has different functions, crawling,
digging, or catching prey
in many mollusks the mantle produces the
hard shell
body structure
bilateral symmetry
digestive system with two openings
circulatory system
most have an open circulatory system
(blood is not always inside blood
vessels.) the organs are located
together so blood can slosh over them
and return to the heart
Cephalopods have a closed circulatory
system
Obtaining Oxygen
most mollusks that live in water have
gills
gills
organ that remove oxygen from the
water to blood CO2 flows out of blood
and into water
cilia move back and forth making
water flow over gills
Three classifications of mollusks based
on physical characteristics
gastropods, bivalves, and cephalopods
Gastropo ds (include snail s and
slug s)
Largest group of mollusks
have one external shell or no shell
live nearly everywhere on earth
obtaining food
herbivores (plant eaters)
or carnivores (meat eaters)
radual
a flexible ribbon of tiny teeth
herbivores use them like sandpaper to
tear into plant tissue
carnivores use differently (oyster drill
uses it to drill through shells and scrap
up the oyster’s/clams soft body tissue
movement
Bivalves (oyster s, scallops, and
clams)
gastropods move by creeping along on
their broad foot. ...may ooze a carpet
of slippery mucus making it easier for
them to move.
mollusks that have two shells held
together by hinges and strong muscles
and are found in all kinds of watery
environments
obtaining food
most are filter feeders
strain tiny organisms from water using
gills
cilia on gills move food particles into
the bivalve’s mouth
movement
larvae of most bivalves float or swim
through the water
Adults stay in one place or use their
foot to move very slowly.
Oysters attach to rocks
movement
protection
Cephalopods (oc topuses, squi ds,
nautiluses and cuttlefishes)
larvae of most bivalves float or swim
through the water
Adults stay in one place or use their
foot to move very slowly.
Oysters attach to rocks
clams move (a little)
grain of sand gets between mantle and
shell and irritates the soft mantle...the
organism coats the irritant with nacre
forming a pearl
ocean dwelling mollusk whose foot is
adapted to form tentacles around its
mouth
not all have shells (nautiluse have
external shells, squid and cuttlefish
have an internal small shell, octopus
have no shells
only mollusks that have closed
circulatory system
obtaining food
cephalopods are carnivores
captures prey using muscular tentacles
then crushing prey in a beak and
scrapes and cuts food with its radula
tentacles contain sensitive suckers that
can taste food without touching it by
sensing chemicals in the water
nervous system
have large eyes and excellent vision
most complex nervous system of any
invertebrate....large brains and can
remember things such as feeding times
in captivity.
movement
swim by jet propulsion squeezing a
current of water out of the mantle
cavity through a tube. turning the tube
they can change direction