1. Echinoderms and Mollusks
Invertebrates 2: Porifera, Cnidarians, Echinoderms, and Mollusks

2. Phylum Mollusca Over 80,000 different species of mollusks
Section 27-4
Over 80,000 different species of mollusks
2nd largest phylum in the animal kingdom.

3. Mollusk Soft bodies covered with a mantle. Most also have shells.
Gills are specialized organs for getting oxygen from water.
Most mollusks move with a muscular foot.

4. The Mollusk Body Plan Section 27-4 Squid Snail Shell Mantle cavity
Foot
Gills
Digestive tract
Clam
Early mollusk

5. Three Kinds of Mollusks
Section 27-4
One-part shells, including snails. These mollusks are gastropods or univalves.
Two-part shelled mollusks are bivalves include clams and oysters.
Cephalopods, includes the octopus and squid, do not have external shells. They also have tentacles to swim and catch prey.

6. The Unknowns Caudofoveata: shell-less wormlike
live in burrows on the deep-sea floor.
Aplacophorans: lack a shell
live in the depths of the ocean
Monoplacopharans: caplike shell, less than 3 cm long
found in the deep ocean.
Polyplacophorans(chitons): Flat long shell w/ 8 plates.
Live on rocky shorelines and graze on plants.
Scaphopods(tusk shells):
Long tube-shaped shell tapered at one end with both ends open.
Burrow into the sand.

7. Class Gastropoda
Stomach-footed mollusks, or gastropods, have broad flat foot on the bottom surface of their bodies.
Snails and slugs are gastropods.
They use the foot for moving from place to place.

9. Interesting Gastropods
Nudibranchs – No Shell (Slugs)
Sea hare – Defense System

10. Class Bivalvia
They have a wedge or hatchet-shaped foot and two shells .
Include clams, muscles, oysters, and scallops.
Use the hatchet-foot
to burrow into the
soft sand and mud.

11. Interesting Bivalves
Scallops – Free Swimming
Giant Clam

12. Class Cephalopoda
The foot of these forms tentacles, or arms, which are located on the animal’s head circling its mouth
Tentacles have suckers that can attach to prey.
Tentacles are used for capturing prey, to crawl and also to cling to rocks.

13. Cephalopods (continued)
Generally good swimmers, especially squid, which are the fastest-swimming invertebrates.
A squid swims by forcing a jet of water from between its mantle and body through a tube.
Cephalopods have larger, better-developed brains than other invertebrates.
Includes octopus and squid.

14. Extinct Cephalopods AMMONOIDEA (Also called ammonites or ammonoids)
Extensive Fossil Record

15. Interesting Cephalopods
Blue-Ringed Octopus – Very small but deadly
Cuttlefish – Changes color

16. Nautilus
Deep Sea Swimmer
Only Cephalopod with a full shell

17. Compare/Contrast Table
Section 27-4
Comparing the Three Major Groups of Mollusks
MOLLUSK GROUP
Gastropods
Bivalves
Cephalopods
SHELL
Shell-less or single-shelled
Two shells held together by one or two muscles
Internal shell or no shell
FOOT
Muscular foot located on ventral side and used for movement
Burrowing species have muscular foot. Surface-dwelling species have either no foot or a “reduced” foot.
Head is attached to a single foot. The foot is divided into tentacles or arms.
EXAMPLES
Snail, slug, sea hare, nudibranch
Clam, oyster, mussel, scallop
Octopus, squid, cuttlefish, nautilus

18. Sea Stars Sand Dollar Sea Urchins Sea Cucumbers
Echinoderms
Sea Stars
Sand Dollar
Sea Urchins
Sea Cucumbers

19. Echinoderms Name echinoderm means “spiny skin.”
The bodies of most echinoderms can be divided into five parts, like wagon wheels with five spokes. = Radial Symmetry

20. Water Vascular System
Have a water vascular system of tubes, or canals, inside and outside of their bodies.
In canals the water is forced, under pressure, into structures called tube feet.
Tube feet are used to crawl
over the bottom of the ocean floor.

21. Digestive system
Some echinoderms, such as starfish, can grip objects tightly enough with their tube feet and arms to pry open clam shells.
Then they move their “reversible”
stomach into the clam
to digest its soft
tissues.

22. The Anatomy of a Starfish
Section 28-1
Section 28-4
Eyespot
Endoskeletal plates
Anus
Stomach
Madreporite
Reproductive glands
Tube foot
Sucker
Ring canal
Radial canal
Digestive glands
Some Examples are….

23. Sea Urchins and Sand Dollars
Parts of the skeleton are fused to form a bony shell.
Have spines that pass through holes in the shell.
The spines work with the tubefeet to help the animal crawl.
Some spines have tiny pinchers on their ends for defense or feeding.

24. Sea Cucumbers
They are long and rounded and have short tentacles around the mouths.
They lie on the sea floor, crawling slowly over the ocean bottom or burrowing in soft mud or sand.

25. Sea Cucumber expelling intestines in defense mode

26. Sea Apple 