1. Mollusks

2. Phylum Mollusca
Second largest animal phylum, has over 100,000 species.
Live in the oceans, streams and even the treetops
Soft bodied animals with either a internal or external shell

3. Form and Function Basic Parts
Foot- Used for movement. This is used differently by different species
Mantle- tissue layer that covers most of the body for example in a squid
Shell- Made by glands in the body that secret (CaCO3) calcium carbonate
Visceral Mass- Contains the internal organs

5. Feeding Radula- thick sandpaper Snail and slugs
Tongue like structure with
100’s of teeth
Used to bring in food or
drill through shell

6. Feeding Continued Snails called cone shells are carnivorous
Proboscis- an extension of the mouth. It pierces the prey, paralyzing it with venom.
Like a harpoon with a poison tip
Basically extends it mouth out to swallow prey
Has poison strong enough to kill a human if handled wrong

7. Feeding still Cont. Octopi - have radula and sharp beaks
- can poison their prey
Clams, Oysters, and Scallops
- filter feeders
- use gills and cilia to move
food into the mouth

8. Diversity of Mollusks
You can tell that snails are very different from clams and that both differ from an octopus.
Would you classify these three mollusks in different groups?
That is what scientists do.
Each of these kinds of mollusks is a member of a different group, or class.

9. Gastropods (class gastropoda)
Mollusks that glide along on a foot underneath their bodies are called gastropods (GAS troh PAHDZ).
Snails, limpets, slugs, and the slug-like nudibranchs are all gastropods.
Most gastropods have one coiled shell.
The shells of limpets, however, are flattened cones.
Slugs and nudibranchs have no shell at all.

10. When you watch a snail moving on the ground, you might think it is scooting on its stomach.
Actually, a gastropod's muscular foot spreads out under its body and is separate from the stomach.
A rippling motion of the foot muscle moves the snail along.

11. Many gastropods eat plants and algae.
Some eat other invertebrates.
As an adaptation for getting their food, gastropods have a tongue-like organ covered with rows of teeth.
It is called a radula (RAJ 00 luh).

12. A gastropod moves its radula back, and forth to scrape off
and scoop up food.
Gastropods that live in water have respiratory organs called gills.
As water flows over the gills, oxygen is extracted.
Gastropods living on land have evolved a cavity inside their Bodies that serves as a simple lung.

13. Bivalves
Mollusks with two shells hinged together make up a second class called the bivalves (BYvalvz).
Clams, oysters, mussels, and scallops are all bivalves.
Like gastropods, bivalves have a muscular foot.
It is normally hidden inside the two shells.
Some bivalves move by hooking the foot in sand, and then pulling themselves along.

14. Bivalves have no head, and most move very little.
Some remain attached to one place.
Movement isn't important because they are filter feeders.
Cilia move water across the gills.
Tiny food particles, such as plankton, are trapped by mucus
on the gills.
Cilia push the food into the animal's mouth.

15. Cephalopods
The octopus and squid are the major members of a third class of mollusks called cephalopods (SEF uh loh PARDZ).
In these mollusks, the foot is divided into tentacles.
The tentacles are located at the head, away from the rest of
the body.

16. Cephalopods are the only mollusks to have a closed circulatory system.
In a closed system, the blood stays in blood vessels.

17. Modern cephalopods all evolved from now-extinct mollusks with external shells.
In the octopus, the shell has disappeared during the process of evolutionary change.
Squids have only small internal shells.
Only cephalopods called nautiluses (NAWTuh luhs uhz) still have the external shells of their ancestors.

18. Cephalopods live in the oceans and most move about freely.
Unlike the filter-feeding bivalves, they are active predators.
Their tentacles are covered with suction cups for grasping prey.
The octopus lives mostly on the ocean floor, crawling around
in search of prey.
Squid swim in the open water.

19. Class Polyplacophora Defining characteristics Poly means many in Latin
Shell forms as a series of 7 to 8 separate plates
Chitons
Phylum Mollusca

20. Chiton Lifestyles
Found close to shore mainly in the intertidal where they live on hard substrates
Very hard to remove from a rock. If removed with knife would curl into ball to protect internal organs.
Most members are herbivores
Phylum Mollusca

21. Chiton Anatomy
Phylum Mollusca

22. Ingestion and Digestion
Radula is used to scrape algae from the rocks
Mouth is anterior and anus is posterior; linear digestive tract
Phylum Mollusca