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I. I.Platyhelminthes Flatworms - Dorsoventrally flattened Simplest bilaterally symmetrical organisms First organs and organ systems** Central nervous system.

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Presentation on theme: "I. I.Platyhelminthes Flatworms - Dorsoventrally flattened Simplest bilaterally symmetrical organisms First organs and organ systems** Central nervous system."— Presentation transcript:

1 I. I.Platyhelminthes Flatworms - Dorsoventrally flattened Simplest bilaterally symmetrical organisms First organs and organ systems** Central nervous system Simple “brain” coordinates muscle movements Incomplete digestive system Mouth but no anus Similar to Cnidaria and Ctenophora Mesoderm** Cell layer between endoderm and ectoderm Gives rise to muscles, reproductive system

2 I. I.Platyhelminthes A. A.Turbellaria Mostly free-living carnivorous species Most commonly seen (Why?) Some live as commensal animals inside other invertebrates (oysters, crabs, etc.)

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4 I. I.Platyhelminthes B. B.Trematoda (Flukes) Most species (6000) Parasitic – Feed on tissues, blood, gut contents Complex life cycles Adults live in vertebrate host (fish, whale, bird) Larvae may inhabit invertebrates (intermediate hosts) Vertebrate eats intermediate host (clam, snail, etc.) C. C.Cestoda (Tapeworms) Parasitic Live in vertebrate intestines Head attaches to intestine wall with suckers or hooks Gutless – absorb nutrients through body wall May reach 50 feet!! (sperm whales)

5 II. II.Nemertea Ribbon worms Cosmopolitan Most common in shallow, temperate regions Complete digestive tract** Mouth and anus Circulatory system** Use long, fleshy proboscis to capture prey Feed on crustaceans and worms May be cryptic or conspicuous Can reach 30 m in length!!

6 III. III.Lophophorates Three phyla – all animals possess lophophore Ciliated hollow tentacles arranged in a horseshoe Suspension feeders Bilateral symmetry, coelom (body cavity), U-shaped gut A. A.Ectoprocta – Bryozoans Colonies consist of interconnected individual zooids Encrusting and lacy forms (CaCO 3 tests) Retractable lophophore B. B.Phoronida – Phoronids, Horseshoe Worms Worm-shaped Agglutinated sediment tubes attached to hard substrate in shallow water C. C.Brachiopoda – Lamp Shells Abundant in fossil record Superficially resemble clams, but shells are dorsal-ventral, not left-right as in mollusks Many attached to substrate with pedicle (short stalk)

7 Bryozoans

8 III. III.Lophophorates Three phyla – all animals possess lophophore Ciliated hollow tentacles arranged in a horseshoe Suspension feeders Bilateral symmetry, coelom (body cavity), U-shaped gut A. A.Ectoprocta – Bryozoans Colonies consist of interconnected individual zooids Encrusting and lacy forms (CaCO 3 tests) Retractable lophophore B. B.Phoronida – Phoronids, Horseshoe Worms Worm-shaped Agglutinated sediment tubes attached to hard substrate in shallow water C. C.Brachiopoda – Lamp Shells Abundant in fossil record Superficially resemble clams, but shells are dorsal-ventral, not left-right as in mollusks Many attached to substrate with pedicle (short stalk)

9 III. III.Lophophorates Three phyla – all animals possess lophophore Ciliated hollow tentacles arranged in a horseshoe Suspension feeders Bilateral symmetry, coelom (body cavity), U-shaped gut A. A.Ectoprocta – Bryozoans Colonies consist of interconnected individual zooids Encrusting and lacy forms (CaCO 3 tests) Retractable lophophore B. B.Phoronida – Phoronids, Horseshoe Worms Worm-shaped Agglutinated sediment tubes attached to hard substrate in shallow water C. C.Brachiopoda – Lamp Shells Abundant in fossil record Superficially resemble clams, but shells are dorsal-ventral, not left-right as in mollusks Many attached to substrate with pedicle (short stalk)

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11 IV. IV.Corals A. A.Biology Phylum Cnidaria, Class Anthozoa (most) Lack medusa stage Hermatypic (reef building) corals produce skeletons made of calcium carbonate Most contain mutualistic zooxanthellae (provide nutrition; enhance calcium carbonate deposition) Many growth forms

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14 IV. IV.Corals A. A.Biology Reproduction Sexual: Most broadcast spawners; some broodersbroadcast spawners Polyp  Planula (planktonic larva)  Polyp Asexual: Fragmentation (can be *very* important) All polyps in a colony genetically identical

15 Fig. 15-4

16 V. V.Coral Reefs A. A.Distribution Living reefs ~ 600,000 km 2 (0.17% of sea floor) Great Barrier Reef = Largest >2000 km long Up to 145 km wide Visible from space

17 V. V.Coral Reefs B. B.Conditions 1. 1.Substrate Primarily in areas with hard substrate 2. 2.Light - Bright (Why?) Rarely develop in water > 50 m deep Continental shelves, around islands, tops of seamounts 3. 3.Temperature Mean annual water temperature > 20 o C Best development at o C

18 Fig Distribution of Coral Reefs

19 V. V.Coral Reefs B. B.Conditions 3. 3.Temperature Too warm also problematic Can cause bleaching and eventually death Bleaching events often occur during periods of unusually warm water Extreme low tide El Niño event Corals live near their upper thermal tolerance levels Corals from warmer waters have higher thermal tolerance levels Fig

20 V. V.Coral Reefs B. B.Conditions 4. 4.Salinity Reefs tend to be absent or poorly developed near mouths of rivers 5. 5.Sediments Turbidity reduces light levels Sediments can smother corals 6. 6.Pollution Corals sensitive to pesticides and other chemicals Fertilizers support growth of algae that smother corals Most corals grow in areas with low nutrient levels 7. 7.Tidal Regime Most corals intolerant of prolonged exposure


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