Post on 08-Jun-2020
10/27/2012
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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
8 rows of ciliated combs for locomotion
biradial symmetry
colloblasts
adhesive cell on tentacles for capturing prey
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
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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
5) sense organs: statocysts & ocelli
6) locomotion by muscular contraction : outer longitudinal & inner circular
7) unique feature: nematocysts (epidermis/gastrodermis)
18) no coelomic cavity
9) all aquatic/mostly marine
shallow marine environments
some fresh water
none terrestrial10) 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
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Five Classes
1) Hydrozoa
(hydra, hydroid, siphonophore (Portuguese Man of War)
2) Scyphozoa (true jellyfish)
3) Staurozoa (stalked jellyfish)
4) Cubozoa (box jellyfish)
5) Anthozoa (sea anenone, hard & soft corals)
I. Hydrozoa
Hydra: freshwater species
no medusa stage
Ectopleura
Corymorpha
budding
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Hydroids
Polymorphism
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Craspedacusta
freshwater hydrozoan
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Portuguese Man of War Physalia physalis
colony of polyps & medusae gas float
II. Scyphozoa (true jellyfish)
scyphozoan medusano velum
thicker mesoglea aids in buoyancy
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III. Staurozoa stalked jellyfish (only polyp) no medusa
8 arms forming tentacular clusters surrounding mouth
nonswimming planula larva develops directly into a polyp
polyps reproduce sexually
IV. Cubozoa (box jellyfish)
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V. Anthozoa
Hard Corals
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cup coral Tubastrea sp.
Hard Stony Corals
closed during day
Montastrea cavernosa polyps
open during night
zoantharian
soft octocorals
8 pinnate tentacles
endoskeleton
spicules with horny protein
spicule
provides flexibility
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Limiting factors
sunlight photosynthesis
water clarity
Corals restricted habitats
shallow depths
warm temperatures
Dying Coral Reefs
human impact
pollution
development
global warming
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Horny (gorgonian) Corals
red gorgonian Melithaea sp. sea fan Subergorgia mollis red whip Ellisella sp.
Soft coral Dendronephthya sp.
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