Animal Diversity 1.pdf

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  • Kingdom AnimaliaAnimals are multicellular heterotrophs, and usually mobileFood is usually ingested and digested in an internal cavity

    Diversity in formMost are invertebrates - Only 1% of all species are vertebrates37 animal phyla (10 to be covered in these lectures)Size ranges from microscopic forms to enormous whalesMost are marine, some are freshwater, few are terrestrial

    Three phyla dominate the land: arthropods, mollusks, chordates

    Animal cells lack cell walls - their cells are relatively flexibleCells are well organized into tissues, except for sponges

    Tissue: made of cells specialized to perform specific function

  • Active movement - made possible by muscles - flexible contractilecells combined with rigid resistant structures - a hard skeletonor incompressible water-filled spaces

    Sexual reproductionAll animals have gametic meiosis - a diploid organism produceshaploid gametes by meiosis in specialized tissues

    Embryonic developmentZygote becomes an adult through process of embryonic development - organization and differentiation of tissue layersPattern of development important in determining evolutionary


  • Classification of AnimalsSubkingdom Parazoa - the SpongesSubkingdom Eumetazoa - all animal phyla with true multicellularity -

    well developed tissuesRadiata - phyla with radial symmetry, two tissue layers

    (Phylum Cnidaria and Phylum Ctenophora)Bilateria - all remaining animal phyla have bilateral symmetry and

    three tissue layers: ectoderm, mesoderm, and endoderm

    Multipleplanes ofsymmetry

    One plane ofsymmetry

  • Within the Bilateria there are types of tissue organization

    Coelom: a body cavity lined completely with mesoderm

    Acoelomates haveno body cavity -flatworms

    Pseudocoelomateshave a body cavity(pseudocoel) withmesoderm to theoutside only -roundworms androtifers

    Coelomates have a coelom - all remaining animal phyla

  • Within the coelomates there are two ways that embryonicdevelopment occursProtostomes have spiral cleavage, the blastopore becomes themouth, mosaic development - molluscs, annelids, arthropodsDeuterostomes have radial cleavage, the blastopore becomes theanus, regulative development - echinoderms, chordates

  • Significance of characteristics

    Bilateral symmetry allows for greater specialization of body regions- a head, midbody, and tail - have different functionsmore efficient locomotiona head with sensory structures and coordination of the nervoussystem - cephalization

    A coelom can be used for storage of energy rich compounds ( fat)reproductive products eggs, sperm, embryosOrgans can develop with separation from other tissuesAllows for specialization of regions of the digestive systemWater filled space that can be used to move body partsAllows for circulation of fluids around organs

  • Phylum Porifera - SpongesMostly marine, few freshwater species,most lack any symmetryThree basic shapes - ascon, sycon, leuconMany are colonial, all are sessile as adultsLittle coordination among cellsSimple mass of cells in a gelatinous matrixCells are specialized

    Choanocytes - collar cells - for feedingEpithelial layer of flattened cells,

    frequently contractile in natureAmoebocytes - found in Mesohyl -

    intermediate gelatinous layerMay possess minute, needles called

    spicules made of silica or calciumMay possess fibrous protein spongin

  • Filter feedersWater flows through system of pores and canalsIn through pores (ostia), out through osculum, passageways linedwith choanocytes capture food and pass it through to other cells inthe sponge body

    Reproductioncan fragment and reorganize for asexual reproductionSexual reproduction via production of egg and sperm

    Sperm differentiate from choanocytes and leave spongeeggs differentiate from amoebocytes in mesohyl

    Sperm are captured by choanocytes and taken into mesohylLarval sponges undergo development within adultsHave external choanocytes when releasedExist as free-swimming planktonic form for a short timeSettle on a suitable substrate to begin transformation to sessileadult life

  • radial symmetryhave endoderm and ectoderm but no

    mesoderm or well developed organsCarnivores, capture food with tentacles

    that surround mouth using specialized stinging cells - cnidocytes

    No blood vessels, No respiratory system, No specialized body cavity,

    Nerve cells organized into nets to coordinate muscle contraction

    Have two body forms - polyp and medusa

    Phylum Cnidaria jellyfish, hydras, anemonaes, coralsnearly all are marine

  • Polyp: cylindrical, tentacles surround mouth

    generally attached to substratesolitary or colonialmay form hard internal or external


    Medusa: bell-shaped, tentacles atedges of bell

    free-floating, mouth faces down

    Some groups have only polyps oronly medusae

    Some groups alternate between thetwo body formsSometimes called alternation ofgenerations

  • An internal digestive cavity enables cnidarians to consume largefood items

    enzymes secreted into a primitive gut begin digestion Particles digested further by cells of gastrodermis Undigested food particles expelled from gut through mouth

    Cnidocytes are cellsspecialized forfood capture anddefense

    Located on tentacles and body

    Each cnidocytecontains a harpoon-like nematocystthat dischargeswhen touched

  • ReproductionPolyps reproduce asexually by budding, form polyps or medusaeSexual reproduction produces fertilized eggsDevelops into a free swimming, ciliated planula larva

  • Classes of CnidariansClass Hydrozoa - HydroidsClass Scyphozoa - JellyfishClass Anthozoa - Corals and

    AnemonesClass Cubozoa - Box Jellyfish

  • Class Hydrozoa - HydroidsMostly marineOften have both polyp and medusa forms

    in life cyclesome colonial forms like ObeliaOthers include Portuguese man-of-war

    and freshwater Hydra

  • Class Scyphozoa - JellyfishConspicuous medusae alternate

    with inconspicuous polyp formsMedusa is bell-shaped, tentacles

    hang around marginsOuter epithelial layer contains

    contractile cellsSex produces planula larvaePolyps can reproduce asexually

  • Class Cubozoa - Box JellyfishOnce included within Class ScyphozoaMedusa is box-shaped, polyps are inconspicuous or unknownTentacle found at each corner of boxStrong swimmers, voracious predatorsMany have powerful stings - some can be fatal to humans

  • Class Anthozoa: Sea Anemones and CoralsSolitary and colonial marine organismspolyp body form onlyCorals secrete hard calcium carbonate

    skeletons and form coral reefsLive primarily in shallow warm waters,

    harbor symbiotic algae - zooxanthellaeWaters that support corals are nutrient

    poor - corals do well because of algae

  • Phylum Ctenophora - Comb JelliesSimilar in biology to Cnidarians,more complex body, no stinging cellsAbundant in the open oceanHave two long retractable tentaclesPossess eight comb-like plates of fused

    cilia for locomotionMany are luminescent