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Mollusca aka the epitome of cool

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1 Mollusca aka the epitome of cool
Briana O’Leary Raissa Largman

2 Animals Four major classes: 1. Polyplacophora: chitons 2. Gastropodia: snails 3. Bivalvia: clams, mussels, scallops, oysters 4. Cephalopoda: squids, octopuses, cuttlefish, chambered nautiluses Briana

3 Polypacophora
Chiton: marine, shell with 8 plates, foot used for locomotion, radula, no head. Raissa

4 Gastropoda Characteristics: Marine, freshwater or terrestrial
Asymmetrical Body Usually has a coiled shell Shell reduced or absent in some Foot for locomotion Radula Gastropoda Briana

5 Bivalvia Marine and Freshwater Flattened shell with two valves Head reduced Paired gills No radula Most are suspension feeders Mantle forms siphons Raissa

6 Cephalopoda Marine Grasping tentacles Usually has suckers Can have shell/radula Locomotion through jet propulsion Briana

7 Basic Body Plan Muscular foot Visceral mass
mantle (fold of tissue over visceral mass) Body Cavity: Present. Fluid filled coelom. Raissa

8 Body Symmetry: Varies. Gastropods: Asymmetrical Other classes are bilaterally symmetrical.

9 Nervous System Nervous System: Present Nerve ring around the esophagus from which nerve cords extend Cephalopods: Highly complex system with brain. Estimated that an octopus has the same intelligence of a house cat. Raissa

10 Circulatory System Open system- heart pumps hemolymph through arteries into body spaces (constantly bathed) except in cephalopods- have closed circulatory systems Briana

11 Digestive System Complete: mouth, anus complex stomach Many use radula to scrape up food, suspension feeders (many bivalves) collect food particles from water that passes over gills Raissa

12 Present: Nephridia: tubular structures that collect fluids and exchanges salts with body tissues.
Excretory System Briana

13 Locomotion/Musculature
Varies Muscular foot (Chitons and Gastropods) Jet propulsion (Cephalopods) Lateral fins: (Cuttlefish) Bivalvia: Mainly sedentary Raissa

14 Skeletal Type Soft bodied but most have a hard shell made of calcium carbonate. In some, the shell is absent or internalized. Briana

15 Sensory Structures/Features
Varies considerably between classes. Cephalopods have complex sensory capabilities. Giant Squids: Largest eyes in the animal kingdom Bivalves: Small eyes and sensory tentacles Gastropods: Eyes at the tips of tentacles Raissa

16 Reproduction Mainly separate sexes with gonads: ovaries or testes. Many snails (gastropods) are hermaphrodites. Life cycle of many marine mollusks includes a ciliated larval stage: trochophore Briana

17 Gas Exchange Marine mollusks have gills. Water enters mantle cavity through a siphon, passes over gills, and then exits mantle cavity through another siphon. Terrestrial snails: lining of the mantle = lung Raissa

18 Other Unique Features There are twice as many species belonging to the phylum Mollusca than there are vertebrates. Gastropods: Torsion – Developing embryo’s visceral mass rotates up to 180 degrees causing its anus and mantle cavity to wind up above its head. Briana

19 QUIZ Name the four classes that comprise Mollusca.
What type of excretory organ is present in Mollusca? A. Kidneys B. Nephridia C. No excretory organ D. Malpighian tubules

20 3. What class has a closed circulatory system?
A. Gastropods B. Bivalves C. Polyplacophora D. Cephalopods 4. Shells of Mollusks are Absent Internalized Present All of the above


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