23.AnimalDiversityPa - Reconstructing the phylogeny of major groups of animals Animal Phylogeny Protostomes There are Two Major Groups of

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Reconstructing the phylogeny of major groups of animals
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Animal Phylogeny: Protostomes
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There are Two Major Groups of Protostomes Two groups of protosomes: lophotrochozoans and ecdysozoans . Derived traits of protostomes: • Anterior brain that surrounds entrance to digestive tract • Ventral nervous system with paired or fused longitudinal nerve cords
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Animal Phylogeny: Lophotrochozoans
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Lophotrochozoans Lophotrochozoans get their name from two traits that were probably ancestral for the group: A lophophore, circular or U-shaped ring of ciliated, hollow tentacles around the mouth. Used for food collection and gas exchange (see movie)
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Lophotrochozoa characteristics Trochophore larvae move by beating a band of cilia:
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Meet the lophotrochozoans Bryozoans : Colonial animals that live in a “house” made of material secreted by the external body wall. Individuals are connected by strands of tissue. Colonies form by asexual reproduction; some can be huge. In some species there is some specialization among colony members.
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Bryozoans Form Colonies
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Bryozoans Form Colonies
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Meet the lophotrochozoans Flatworms : Tapeworms and flukes are internal parasites, particularly of vertebrates. • No digestive tract: they absorb digested food from gut of host • Cause serious diseases such as schistosomiasis • Have complex life cycles with multiple hosts Turbellarians are free-living species
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Flatworms Flatworms have no gas transport system, all cells must be near the surface—hence the dorsoventrally flattened body form. Digestive tract of free-living species is a many- branched blind sac. Provides large surface area for nutrient absorption. Free-living species glide over surfaces, powered by bands of cilia (see movie).
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Flatworm
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Meet the lophotrochozoans Rotifers : Most are tiny, the size of protists. • A ciliated corona on the head sweeps food particles into mouth (see movie) Bdelloid rotifers are only known to have females (so how do they persist?)
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Asexual bdelloid rotifers avoid the effects of Muller’s ratchet by: A. The appearance of rare males, which allows rare sex B. Exchanging genetic material without reproduction, as in some protists C. Picking up the genetic remains of dead organisms from the environment D. Exchange of genes among “females” in association with reproduction E. None of the above
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Bdelloid Rotifer
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Meet the lophotrochozoans Ribbon worms : • Have a hollow, muscular proboscis , the feeding organ. The proboscis may extend much of the length of the body, and is everted for feeding. May be armed with stylets to pierce prey and inject paralytic toxins.
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Ribbon Worm
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Ribbon Worm
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Meet the lophotrochozoans: Phoronids
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Phoronids
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Brachiopods : Solitary, with two-part shell—dorsal and ventral. Lophophore is inside the shell.
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This note was uploaded on 09/11/2011 for the course PHY 57040 taught by Professor Lang/ritchie during the Spring '10 term at University of Texas at Austin.

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23.AnimalDiversityPa - Reconstructing the phylogeny of major groups of animals Animal Phylogeny Protostomes There are Two Major Groups of

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