Molluscaaka the epitome of cool

Briana O’LearyRaissa Largman

http://www.greenexpander.com/wp-content/uploads/2007/12/octopus.jpg

Animals

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

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Polypacophora

http://reefguide.org/pix/thumb2/chiton4.jpg

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

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Gastropoda

• http://photography.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Photography/Images/Content/green-snail-laman-400957-sw.jpg

Characteristics: Marine, freshwater or terrestrialAsymmetrical BodyUsually has a coiled shellShell reduced or absent in someFoot for locomotionRadula

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Bivalvia

Marine and FreshwaterFlattened shell with two valvesHead reducedPaired gillsNo radulaMost are suspension feedersMantle forms siphons

http://www.barrierreefaustralia.com/IMAGEGALLERY/giant-clam.jpgRaissa

Cephalopoda

MarineGrasping tentaclesUsually has suckersCan have shell/radulaLocomotion through

jet propulsion

http://fractalontology.files.wordpress.com/2008/03/nautilus.jpg

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Basic Body PlanBody Cavity: Present. Fluid filled coelom.

http://www.bio.miami.edu/dana/pix/ham.jpg

-Muscular foot-Visceral mass- mantle (fold of tissue over visceral mass)

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Body Symmetry: Varies. Gastropods: Asymmetrical

Other classes are bilaterally symmetrical.

http://open.live.bbc.co.uk/dynamic_images/naturelibrary_640_credits/downloads.bbc.co.uk/earth/naturelibrary/assets/o/oc/octopus/octopus_1.jpg

http://www.bio.miami.edu/dana/pix/bodysymmetry.jpg Briana

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.

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Circulatory System

Open system- heart pumps hemolymph through arteries into body spaces (constantly bathed)

except in cephalopods- have closed circulatory systems

http://www.cartage.org.lb/en/themes/sciences/lifescience/GeneralBiology/Physiology/CirculatorySystem/CirculatorySystem/TypesCirculatory/circsys_2.gif

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Digestive System

Complete: mouth, anus complex stomachMany use radula to scrape up food, suspension feeders (many bivalves) collect food particles from water that passes over gills

http://kentsimmons.uwinnipeg.ca/16cm05/1116/33-21-ClamAnatomy-L.jpg

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Excretory System

Present:Nephridia: tubular structures that collect fluids

and exchanges salts with body tissues.

http://www.sharky1.com/Images/marine/mini%20cuttlefish.jpgBriana

Locomotion/Musculature

Varies Muscular foot (Chitons

and Gastropods) Jet propulsion

(Cephalopods) Lateral fins: (Cuttlefish)

Bivalvia: Mainly sedentary http://www.pc.gc.ca/~/media/pn-np/bc/pacificrim/e-f/E-17_RAZOR_CLAM.ashx

http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Cephalopoda/Sub-squid.JPG

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Skeletal Type

Soft bodied but most have a hard shell made of calcium carbonate.

In some, the shell is absent or internalized.

http://bama.ua.edu/~musselp/graphics/presentations/shell_show_2004_1.jpg

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Sensory Structures/FeaturesVaries 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

http://www.nefsc.noaa.gov/press_release/2008/SciSpot/ss0810/T%20megalops%202038%20copy.jpg

http://www.genomicon.com/wp-content/uploads/2009/04/snaileye.jpg

http://www.augsburg.edu/home/biology/photoofmonth/scallopeyes-wide-big.jpg

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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

http://www.nicertutor.com/doc/class/bio1903/Locked/media/ch32/32_13Trochophore.jpg

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Gas ExchangeMarine 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

http://kentsimmons.uwinnipeg.ca/16cm05/1116/33-21-ClamAnatomy-L.jpg

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Other Unique FeaturesThere 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.

http://www.palaeos.com/Invertebrates/Molluscs/Gastropoda/Images/torsion.gif

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QUIZ

1. Name the four classes that comprise Mollusca.

2. What type of excretory organ is present in Mollusca?

A. Kidneys B. Nephridia C. No excretory organ D. Malpighian tubules

3. What class has a closed circulatory system? A. Gastropods B. Bivalves C. Polyplacophora D. Cephalopods

4. Shells of Mollusks are A.AbsentB. InternalizedC. PresentD.All of the above

http://www.fish.govt.nz/NR/rdonlyres/836B96BF-12FE-417D-AB49-4B46B2DB8729/0/ColossalSquid.jpg