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Kingdom Animalia Ch. 12- Phylum Mollusca. Key Characteristics of Mollusks 2 nd largest animal phylum Marine, freshwater, and terrestrial Seven classes.

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Presentation on theme: "Kingdom Animalia Ch. 12- Phylum Mollusca. Key Characteristics of Mollusks 2 nd largest animal phylum Marine, freshwater, and terrestrial Seven classes."— Presentation transcript:

1 Kingdom Animalia Ch. 12- Phylum Mollusca

2 Key Characteristics of Mollusks 2 nd largest animal phylum Marine, freshwater, and terrestrial Seven classes True coelem- gut and internal organs suspend from body wall; cushioned by fluid Trochophore-Trochophore- Free-swimming larval stage propels with cilia

3 Key Characteristics of Mollusks Body cavity Bilateral symmetry 3-part body plan: –Visceral mass –Visceral mass- central section with organs –Mantle- –Mantle- Heavy fold of tissue forms outer layer of body –Foot- –Foot- Muscular region for locomotion Organ systems: Excretion, circulation, respiration, digestion, and reproduction Shell- Exoskeleton made of protein, calcium carbonate, and hard minerals –Univalve- one part shell –Bivalve- two part shell Radula- Tongue-like organ in mouth with thousands of backward-curving teeth in rows; Not in bivalves

4 Mollusk Body Plan

5 Organ Systems Excretion: –Coelem collects waste fluid –Nephridia- –Nephridia- tubular structures recover useful molecules to be reabsorbed by tissues –Fluid waste leaves through pores in mantle Circulation: –Digestive tube surrounded by mesoderm; barrier for diffusion of nutrients into tissues –Blood carries nutrients and oxygen to tissues and removes waste and carbon dioxide –3 chambered heart; open circulatory system –Exception: Octopus and squid; closed circulatory system

6 Organ Systems Respiration: –Most have gills; extract 50% or more oxygen –Sea snail gas exchange through skin –Terrestrial snails- no gills; thin moist membrane acts as primitive lung –Snails most active at night and after rain –When dry, pull into shell and plug opening with mucus Reproduction: –Most distinct male and female individuals –Some snails and slugs hermaphrodites –Some oysters and sea slugs change back and forth from male to female –Octopus, freshwater snails, some freshwater mussels have no free- swimming larvae; juvenile stage hatches from egg 4C34-96E5-4F6BAA4B7DFE&blnFromSearch=1

7 Class Gastropoda Snails and slugs Microscopic to 1 m in length Mostly univalve; slugs and nudibranchs lost shell completely Foot secretes mucus fro slimy path to glide on Pair of tentacles on head with eyes on end Herbivores use radula to scrape algae or tear leaves Some active predators: sea slugs, whelks, and oyster drills (radula bores holes in other mollusk shells), and cone shells (use poison-tipped radula) –Whelks used by native-americans to make beaded wampum belts for trading or gifts to tribal leaders Land snails, genus Helix, raised on snail farms for food Few marine species, such as conchs, delicacies

8 Gastropods


10 Class Bivalvia Oysters, clams, scallops and mussels Two-part hinged shell secreted by mantle Adductor muscles-Adductor muscles- Connect valves and allow for opening and closing; water propels when snapped shut No distinct head region nor radula Nerve ganglion is simple brain; simple sense organs Either male or female; few hermaphrodites Sperm and egg release into water for fertilization –Trochophore larvae –Mussels brood in pouches on gills –Larvae are parasites on fish

11 Class Bivalvia siphonsFilter feeders; cilia on gills draws water in through siphons (hollow tubes) Mucus covering gills traps marine organisms and organic matter which is directed to the mouth Mussels attach to rocks in intertidal zones Scallops swim Oysters permanently attach to rocks –Produce pearls when tiny foreign objects get trapped between mantle and shell nacre () –Coat them with nacre (mother-of-pearl) in successive layers –Fine pearls contain mineral crystals which act like prisms for color

12 Bivalves

13 Class Cephalopoda Squid, octopus, cuttlefish, and nautiluses tentaclesBody with large head attached to tentacles (foot divided into numerous parts) Tentacles equipped with suction cups or hooks –Squids- 10 tentacles –Octopus- 8 tentacles –Nautilus- Between 80 and 90 tentacles Lack an external shell; except nautilus Squid and cuttlefish have small internal shell –Cuttlefish bones sometimes used in bird cages for calcium 44E7-94DD-4D985B263D1E&blnFromSearch=1

14 Class Cephalopoda Most intelligent of all invertebrates Complex nervous system with well-developed brain Octopuses can be trained to classify objects; square from cross Some have color vision Squid have very large eyes for collecting light; Giant squid is largest invertebrate with largest animal eyes Move by water propulsion Some release dark fluid when threatened to conceal their escape –Cuttlefish ink used by many famous historical artists

15 Class Cephalopoda Active marine predators Feed on fish, mollusks, crustaceans, and worms Tentacles nab prey and pull into mouth Strong, beak-like jaws tear apart Radula pulls pieces into mouth Blue-ringed octopus: Extremely poisonous

16 Cephalopods EE-D862-4F4E B1CAA1BA7BA&blnFromSearch=1

17 Ammonites Extinct cephalopod Fossil records Had conical shell Only living cephalopod is the nautilus

18 Squid vs. Octopus SquidOctopus 10 tentacles8 tentacles Inner shellNo shell Change color- camouflageNo ability to change color Swim tentacles firstSwim head first

19 Class Caudofoveata Wormlike mollusks with cylindrical, shell-less body Deep-water marine burrowers No eyes Chaetoderma

20 Class Aplacophora Shell, mantle and foot lacking Worm-like Marine and burrowing Neomenia

21 Class Monoplacophora Single, arched shell Broad, flat foot Marine Neopilina

22 Class Scaphopoda Body enclosed in a tubular shell Open on both ends No head Tentacles used for deposit feeding Dentalium

23 Class Polyplacophora Chitons –Reduced head –Flattened foot –Shell with eight articulating dorsal valves –Most feed on algae

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