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http://www.underwater.com.au/content/5192/blue_ringed_octopus.jpg

Objectives: 1) Describe the 3-part

body plan of a mollusk. 2) Identify

the 3 major classes of mollusks,

and provide examples.

Characteristics of Mollusks1)Coelom: True body cavity where organs including the gut are suspended.2)Trochophore: ciliated larva

3) Second largest phylum4) Bilateral Symmetry5) All mollusks except bivalves, have a radula, a rasping tongue like organ (containing 1,000s of tiny teeth) used to get food.

Mollusk Body Plan3 Parts#1 Visceral Mass: central part that contains the mollusk's organs#2 Mantle: Tissue that folds around the visceral mass like a cape.#3 Foot: Muscular region used for movement.

Organ SystemsCirculatory, respiratory, digestive, and reproductiveShellsMost mollusks have 1 or 2 shells

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3 Classes of Mollusks#1 GastropodsExamples: Slugs and snails (including sea slugs)Most have a single shellTentacles with eyes at the tips.Locomotion: can glide on mucus secreted from the footFeeding Habits:

1) Terrestrial Species: Mainly herbivoresMarine species: Some are predators using radula to bore holes through the shells

of other mollusks.

#2 Bivalves1) Examples: Clams and oysters

2) Live mostly in marine habitats.

3) Shells are secreted by the mantle.

4) Basic Body Plan: 2-part hinged shell.

6) Each part of the shell is connected to 2 adductor muscles which control the opening and closing of the shell.

7) No true head or radula.

8) Bivalves are either male or female.

9) Fertilization is outside the body.

10) Bivalves are filter feeders that use a siphon.

#3 Cephalopods1) Examples: Squids, octopi, and nautiluses2) Basic Body Plan: Large head attached to tentacles (modified foot)3) Most intelligent out of all invertebrates due to a well developed brain.4) Cephalopod eyes are very advanced, some can see color. 5) Cephalopods are predators. They possess a strong beak as well as a radula.

#4 Chitons

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