1. Mollusca
Soft bodied animals

2. Mollusca General Info 150,000 known species
Most mollusks are marine, but some live in fresh water environments
Mollusks are soft-bodied animals that are sometimes protected by a hard shell

3. Symmetry in Mollusca
In the beginning of the life cycle of a mollusk, bilateral symmetry is present, but this may be lost by adulthood as they have spiral development

4. Body Development in Mollusks
3 main parts: muscular foot, a visceral mass, and a mantle
The muscular foot is used for movement
The visceral mass contains most of the internal organs
The mantle is a fold of tissue that secretes the shell if present, covers the visceral mass
The shell secreted by the mantle is made of CaCO3

5. Movement
In Polyplacophora, Gastropoda, and Bivalvia, a muscular foot is used for locomotion
In Cephalopods, siphon made from the mantle allows jet propulsion

6. Germ Layers and Coelom
Open circulatory system, where the body cavity is a blood-filled hemocoel filled with hemophyll (blood and lymph between organs)

7. Life Cycle/Reproduction
Starts with a ciliated larva, otherwise known as a trochophore
No true segmentation unlike Annelids
Normal sexual reproduction is present, although some are hermaphrodites
Most have external fertilization

8. Specialized Tissue
The radula is a tongue-like structure that scrapes up food and is modified into a beak in the octopus
The mantle cavity is a water-filled chamber that houses the gills, anus, and excretory pores
Torsion is a process in Gastropoda where one set of muscles grows faster than the other, which creates the shell to grow in a spiral pattern

9. Chiton (Polyplacophora) Octopus (Cephalopoda)
Snail (Gastropoda)
Squid (Cephalopoda)
Scallops (Bivalvia)

10. Mollusk behavior
nudibranch
chiton
octopus camoflauge, beak, and feeding
flexible octopus body
octopus intelligence
swimming clam
burrowing clam
chambered Nautilus