1. TSW identify and describe the basic characteristics of mollusks

2. What is a mollusk?
Soft-bodied animal with an internal or an external shell
Very diverse phylum, but all share similar developmental stages
Many have TROCHOPHORE larvae: free-swimming larval stage of aquatic mollusks

3. Form & Function True COELOMS surrounded by mesoderm tissue
Complex, interrelated organ system

4. Body Plan
4 Main Parts
FOOT: Muscular, used for crawling, burrowing, & capturing prey
MANTLE: Thin layer of tissue covering the mollusk’s body like a cloak
SHELL: Made of calcium carbonate; has been lost in some groups
VISCERAL MASS: Internal organs

6. Feeding
Can be herbivores, carnivores, filter feeders, detritivores, or parasites

7. Feeding Structures
RADULA: Flexible, tongue-like structure to which hundreds of tiny teeth are attached
SIPHON: Tubelike structure through which water enters and leaves the body

8. Respiration
Aquatic mollusks typically breathe using gills inside their mantle cavity

9. Circulation
Oxygen & nutrients are carried to all parts of a mollusk’s body via an open or closed circulatory system
OPEN: Blood is pumped through vessels by a simple heart sinuses gills  heart
Works best in slow-moving mollusks (snails & clams) b/c their demand for oxygen is low

11. Excretion
Cells release nitrogen-containing waste into the blood in the form of ammonia
Nephridia: tubular structures that collect fluids from the coelom and exchange salts and other substances with body tissues as the fluid passes along the tubules for excretion.

12. Response
Complexity varies depending on the species

13. Movement
Rippling motion of the foot (snails)
Jet propulsion (octopi)

14. Reproduction Sexually via external fertilization
Some have internal fertilization
Some are hermaphrodites

15. Groups of Mollusks
Divided into three main groups depending on the characteristics of the foot and shell
Gastropoda
Bivalvia
Cephalopoda

16. Gastropoda Gastropods Shell-less or single-shelled
Move using a muscular foot on the ventral side
Examples: Pond snails, sea butterflies, sea hares, limpets, & nudibranchs

18. Bivalvia
Bivalves
2 shells that are held together by 1 or 2 powerful muscles
Most stay in one lace much of the time
Many are filter feeders, but some use long, muscular extensions to collect food

19. Bivalve: Examples
Clams, oysters, mussels, and scallops

20. Cephalopoda Cephalopods
Soft-bodied, head is attached to a singular foot that is divided into tentacles or arms
Most active of all mollusks
Small internal shell or no shell at all
Numerous, complex sense organs

21. Cephalopods: Examples
Octopi, squid, cuttlefish, nautilus