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9/20/2011
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Radiate Animals
Phylum Ctenophora
>9,000 species
specialized cells (cnidocytes)
specialized stinging organelle, the nematocyst
fossils >700 mya
<100 species
Phylum Cnidaria
comb jellies/sea walnuts
Unicellular (acellular)
protozoan protists
Multicellular (metazoa)
Poorly defined
tissue layersDiploblastic Triploblastic
PoriferaPlacozoa
CnidariaCtenophora
Priapulida
Chaetognatha
Gastrotricha
Entoprocta
Loricifera
PlatyhelminthesRhynchocoela (Nemertea)
Mesozoa
Gnathostomulida
Rotifera
NematodaKinorhyncha
Acanthocephala
Nematomorpha
Annelida
Mollusca
ArthropodaOnychophora
Pentastomida
Pogonophora
Sipuncula
Echiura
EchinodermataHemichordata
Chordata
Brachiopoda
Phoronida
Bryozoa
Uncertain Acoelomate Coelomate Pseudocoelomate
Protostomes Uncertain (misfits) Deuterostomes
9/20/2011
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8) tentacles: extensible projections for food capture with abundant nematocysts
Cnidarian Characteristics1) diploblastic: two well-defined germ layers: ectoderm & endoderm
mesoderm may be derived from ectoderm (ectomesoderm)
2) internal body cavity: the gastrovascular cavity
3) extracellular digestion occurs in the gastrovascular cavity;
gastrodermal cells enzymes for cellular digestion
4) nerve cells; nerve net but no central nervous system