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Radiate Animals Phylum Cnidaria >9,000 species fossils >700 mya
specialized cells (cnidocytes) specialized stinging organelle, the nematocyst
Phylum Ctenophora <100 species comb jellies/sea walnuts
Unicellular (acellular) Multicellular (metazoa)
protozoan protists
Poorly defined Diploblastic Triploblastic tissue layers Cnidaria Porifera Ctenophora Placozoa
Uncertain Acoelomate Coelomate Pseudocoelomate
Priapulida Rotifera Chaetognatha Platyhelminthes Nematoda Gastrotricha Rhynchocoela (Nemertea) Kinorhyncha Entoprocta Mesozoa Acanthocephala Loricifera Gnathostomulida Nematomorpha
Protostomes Uncertain (misfits) Deuterostomes
Annelida Mollusca Echinodermata Brachiopoda Arthropoda Hemichordata Phoronida Onychophora Bryozoa Chordata Pentastomida Pogonophora Sipuncula Echiura
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Cnidarian Characteristics 1) 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 5) sense organs: statocysts & ocelli 6) locomotion by muscular contraction : outer longitudinal & inner circular 7) unique feature: nematocysts (epidermis/gastrodermis) 8) tentacles: extensible projections for food capture with abundant nematocysts
9) all aquatic/mostly marine shallow marine environments some fresh water none terrestrial 10) some symbiotically e.g. with algae in reef-building corals 11) radial symmetry: oral & aboral ends 12) dimorphism: free-swimming medusae & sessile polyps: ecological niches 13) some: exoskeleton or endoskeleton: chitinous, calcareous or protein 14) gastrovascular cavity: a single opening serving as both mouth & anus 15) reproduction: either asexual or sexual 16) planula larva may be present 17) no excretory or respiratory system 18) no coelomic cavity
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Five Classes I. Hydrozoa
Ectopleura
Hydra: freshwater species no medusa stage budding
Corymorpha
Hydroids
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Polymorphism
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Craspedacusta
freshwater hydrozoan
Portuguese Man of War Physalia physalis
colony of polyps & medusae gas float
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II. Scyphozoa (true jellyfish)
scyphozoan medusa no velum thicker mesoglea aids in buoyancy
III. Staurozoa stalked jellyfish (only polyp) no medusa
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IV. Cubozoa
V. Anthozoa
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Hard Corals
Hard Stony Corals
cup coral Tubastrea sp. closed during day open during night Montastrea cavernosa polyps zoantharian
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soft octocorals 8 pinnate tentacles endoskeleton spicules with horny protein provides flexibility
spicule
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Corals restricted habitats shallow depths warm temperatures
Limiting factors sunlight photosynthesis water clarity
Dying Coral Reefs human impact pollution development global warming
Horny (gorgonian) Corals
red gorgonian Melithaea sp. sea fan Subergorgia mollis red whip Ellisella sp.
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Soft coral Dendronephthya sp.
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