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27 Sept.2014Mollusks.ppt1 Coelomate Protostomes Phylum Mollusca Phylum Annelida Phylum Arthropoda.

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Presentation on theme: "27 Sept.2014Mollusks.ppt1 Coelomate Protostomes Phylum Mollusca Phylum Annelida Phylum Arthropoda."— Presentation transcript:

1 27 Sept.2014Mollusks.ppt1 Coelomate Protostomes Phylum Mollusca Phylum Annelida Phylum Arthropoda

2 27 Sept.2014Mollusks.ppt2 Protostomes Three major phyla share three embryonic characters Spiral cleavage Mouth develops at site of blastopore (1 st mouth) Mesoderm develops from lips of blastopore as solid masses, splits “split” coelom

3 27 Sept.2014Mollusks.ppt3 Protostomes Formation of Mesoderm and Coelom Solid masses of mesoderm separate from lips of blastopore. Split opens in mesoderm to form “split” coelom

4 27 Sept.2014Mollusks.ppt4 Phylum Mollusca Phylum Mollusca (Greek “soft”) ~100,000 species, 2 nd largest phylum Body plan Tube-in-tube, Protostomous Bilateral symmetry Coelomate, “split” coelom Marine, aquatic, terrestrial

5 Phylum Mollusca Body with three parts Visceral mass (“torso”) Mouth, gut, heart, gill, reproductive organs Mantle Sheet of tissue attached to middle of back Mantle cavity = space between mantle & visceral mass Foot Single muscular sheet contacts substrate Creeps with 100’s of little muscles 27 Sept.2014Mollusks.ppt5

6 27 Sept.2014Mollusks.ppt6 Phylum Mollusca Visceral mass (“torso”) Mantle  Mantle cavity = space between mantle & visceral mass Foot

7 27 Sept.2014Mollusks.ppt7 Phylum Mollusca Unique, distinguishing characters Mantle Mantle cavity Foot Radula Tooth-bearing scraping “jaw”

8 27 Sept.2014Mollusks.ppt8 Phylum Mollusca Ways the needs of cells are met Food Scrape algae etc. or filter-feeders Squids and Octopus are predators O 2 and CO 2 exchange Gills, or mantle cavity as “lung” Waste removal “kidney” with duct to mantle cavity

9 27 Sept.2014Mollusks.ppt9 Phylum Mollusca Style in “stomach” Hard crystalline rod of digestive enzymes Spins in stomach, wraps string of mucus and food Ground away at posterior end along with mucus and food

10 27 Sept.2014Mollusks.ppt10 Phylum Mollusca Special concerns of a multicellular animal Circulation: Open circulatory system Coordination: Brain & ventral nerve cords, Structural support: Hydrostatic &/or shell Movement: Muscles in foot Maintenance of water balance: “kidney” Reproduction Usually sexual, sexes usually separate, some hermaphrodites

11 27 Sept.2014Mollusks.ppt11 Phylum Mollusca Coelom reduced to pericardial cavity Open Circulatory System No blood vessels (almost) Blood pumped forward through head, then oozes through visceral mass, around organs, muscles, gills, back to heart Hemocoel

12 27 Sept.2014Mollusks.ppt12 Phylum Mollusca Nervous system Brain small, surrounds esophagus Pair of visceral nerve cords Pair of pedal nerve cords

13 27 Sept.2014Mollusks.ppt13 Phylum Mollusca  Class Polyplacophora chitons  Class Gastropoda snails, slugs, nudibranchs  Class Bivalvia clams, mussels, oysters, shipworm, etc.shipworm  Class Cephalopoda squids, Octopus, cuttlefish, Nautilus

14 27 Sept.2014Mollusks.ppt14 Phylum Mollusca  Class Polyplacophora Chitons Thick mantle with eight shell plates Scrape algae, etc. from rocks

15 27 Sept.2014Mollusks.ppt15 Phylum Mollusca  Class Gastropoda snails, slugs, nudibranchs Torsion Bending & twisting of gut Conical, spiral shell

16 27 Sept.2014Mollusks.ppt16 Phylum Mollusca  Class Gastropoda

17 27 Sept.2014Mollusks.ppt17 Phylum Mollusca  Class Bivalvia clams, mussels, oysters, etc. Filter feeders Gill used as filter Radula usually lost Shells on left, right

18 27 Sept.2014Mollusks.ppt18 Phylum Mollusca  Class Cephalopoda Octopus, Squids, Nautilus, cuttlefish, Siphon on mantle edge “rocket” away from predators Tentacles with suction cups

19 27 Sept.2014Mollusks.ppt19 Phylum Mollusca  Class Cephalopoda Octopus Complex behavior, learning


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