Animal evolution

Animal evolution - Animal Evolution Porifera sponges 5,000...

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Unformatted text preview: Animal Evolution Porifera sponges 5,000 living sponge species Three Main Groups: hexactineuida (glass sponges) demospangia calcarea (calcareous sponges) no coelom, organs, or skeleton no urinary, cardiovascular, respiratory or nervous system cellular grade of organization Evolutionary Time Frame Among the oldest known fossils began in late Precambrian developed from first multi-cellular organism Tissues Two layers of cells layers are separated by gelatinous region called mesohyl Spongocoel the central cavity internal water chambers water flows in and out of the osculum coanocytes are flagellated, collar cells these line the spongocoel help propel water through cell Reproduction Reproduce sexually or asexually Hermaphrodites this means they are male and female produce both eggs and sperm gametes arise from choanocytes or amoebocytes eggs reside in the mesohyl, while sperm cells are carried out of the sponge by water current fertilization occurs in the mesohyl zygotes develop into flagellated, swimming larvae in asexual reproduction buds are produced are often packets of several cells inside a protective coating called gemmule Locomotion No muscles Digestion No mouths carnivores archaiout, cells ingest and digest food suspension feeders filter feeders they collect bacteria taken from the water tiny pores in outer walls these draw water called ostia cells in sponge walls filter water water is pumped through the body and out larger opening (oscula) flow of water is unidirectional driven by beating of flagella which line the surface of chambers and are connected by a series of canals Cnidaria corals, jellyfish, hydra Four Main Classes Anthozoa (corals, anemones, sea pens, sea fans, sea anemones) Cubozoa (box jellies) Hydrozoa (diverse group of siphonophores, hydroids, five corals, medusae, obella) Scyphozoa (true jellyfish, jellies, sea wasps, sea nettles) do not have a cardiovascular system Evolutionary Time Frame Corals - first appeared in Vendian few fossils in Cambrian period, but identifiable corals began evolutionary radiation in Early Ordovician Period wiped out at end of Permian Period mass extinction event in which 95% of all marine invertebrate species became extinct scleractinian corals appeared in the middle of the Triassic (15 million years later) became dominant hermatypic (reef-building) organisms in shallow tropical marine habitats Cnidaria first appeared during the Pre-Cambrian era Tissues Simplest organisms at tissue level cells are organized in true tissues two cell layers - outer ectoderm (epidermis) and inner endoderm (gastrodermis) Outer Ectoderm contains cnidocysts (stinging cells) Inner Endoderm lines gut (sometimes divided by septa) Mesoglea (between layers) layer of jelly-like substance contains scattered cells and collagen fibers Excretion...
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This note was uploaded on 11/23/2011 for the course BIO 100 taught by Professor Robinson during the Fall '08 term at BYU.

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Animal evolution - Animal Evolution Porifera sponges 5,000...

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