2. • Examples: snails, slugs, clams, oysters,
octopuses
• Most of these animals live in the ocean.
• Most mollusks fit into 3 classes:
– Gastropods: includes slugs and snails
– Bivalves: includes clams and other
shellfish with 2 shells
– Cephalopods: includes squids and
octopuses

3. • How Do Mollusks Eat?
– Snails and slugs eat
with a ribbonlike organ
—a tongue covered
with curved teeth
called a radula.
– Clams and oysters
attach to one place
and use gills to filter
tiny plants, bacteria,
and other particles
from water
– Octopuses and squids
use tentacles to grab
their food and place it
in their powerful jaws.

4. • Ganglions and Brains
– Special ganglia
control breathing,
movement, and
digestion.
Octopuses and
squids have the
most advanced
nervous system
– Cephalopods are
thought to be the
smartest
invertebrates

5. The Colossal Squid (Mesonychoteuthis hamiltoni, from Greek mesos (middle),
nychus (claw), and teuthis (squid)), sometimes called the Antarctic or Giant
Cranch Squid, is believed to be the largest squid species in terms of mass. It is
the only known member of the genus Mesonychoteuthis. Though it is known
from only a few specimens, current estimates put its maximum size at 12–14
metres (39–46 feet) long,[1] based on analysis of smaller and immature
specimens, making it the largest known invertebrate.

6. • Pumping Blood
– Open circulatory
system: circulatory fluid
is not contained entirely
within the vessels
– Closed Circulatory
System: heart
circulates blood through
a network of blood
vessels that form a
closed loop

7. • Mollusk Bodies
– Mollusks are known for their broad, muscular foot.
The foot helps the animal move. In gastropods, the
foot makes mucus that the animal slides along.
– The gills, gut, and other organs form the visceral
mass. It lies in the center of a mollusk’s body.
– A layer of tissue called the mantle covers the visceral
mass. The mantle protects the bodies of mollusks
that do not have a shell.
– In most mollusks, the outside of the mantle secretes
a shell, which protects it from predators and from
drying out.

9. • Often called segmented
worms because their bodies
have segments.
• A segment is an identical, or
almost identical, repeating
body segment.
• Have bilateral symmetry, but
are more complex
• Have a closed circulatory
system and a complex
nervous system with a brain.
• A nerve cord connects the
brain to a ganglion in each
segment.

10. • Earthworms
– Most familiar annelid
worm
– Has 100 to 175
segments
– Eat material in soil and
leave behind wastes
called castings.
– Earthworms improve
garden soil by digging
tunnels.
– To move, earthworms
use stiff hairs, or
bristles, on the outside
of their body.

11. • Marine Worms
– Called polychaetes,
which means “ many
bristles”
– They are covered in
bristles and come in
many colors
– Most of these worms
live in the ocean.
– Some eat mollusks
and other small
animals, or filter small
pieces of food from the
water

12. • Leeches
– Known as parasites that
suck other animals’
blood
– Some are scavengers
that eat dead animals,
others are predators that
eat insects, slugs, and
snails.
– Leeches are sometimes
used after surgery to
prevent dangerous
swelling near a wound.
– Doctors can use a
chemical in leeches that
encourages blood flow to
prevent blood clots.