ANIMAL KINGDOM
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ABBOTTSCOLLEGE
PHYLUM CNIDARIA
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PHYLUM CNIDARIA4
Includes between 9 000 and 11 000
species
Includes the plant like hydroids, the
flower like sea anemones, the jelly-fish, bluebottles and
the hard corals
BODY PLAN OF CNIDARIA5
Acoelomate (have no body cavity) Radial symmetry Diploblastic tissue layers Digestive cavity with a single opening
The body wall is made up of three layersBut there are only two layers of cells (the ectoderm and endoderm)The middle layer (mesogloea) is jelly
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DIPLOBLASTIC TISSUE LAYERS
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The ectoderm forms the epidermis
The endoderm forms the gastrodermis (aroundthe gut)
There is a layer of jelly between the two = mesogloea
BODY WALL CNIDARIA
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RADIAL SYMMETRY8
Suits their sessile or free floating mode of living
Makes them aware of what is happening all around them
DIGESTIVE CAVITY WITH A SINGLE OPENING
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Serves as both a mouth and an anus
Inefficient digestive system Have a ring of tentacles around
the opening to catch food Have specialised stinging cells
or cnidocytes Which contain stinging
organelles called nematocysts to capture their prey and defend themselves against predators
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Hydra is a genus of small, simple, fresh-water animals that possess radial symmetry. Hydra are predatory animals belonging to the phylum Cnidaria
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REPRODUCTION16
Have a dimorphic life cycle (develop two basic body forms)
Medusa Free swimming and umbrella shaped Develops gonads Reproduces sexually to produce a free-swimming
planula larva Polyp
Develops from the larva May occur singly (eg anemones) Or in enormous marine colonies (eg corals)
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Life cycle Cnidaria
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CoralCoral ReefCorals are marine invertebrates in phylum Cnidaria typically living in compact colonies of many identical individual "polyps".
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TEXTBOOK PAGE 78
LEARNING ACTIVITY 1
QUESTIONS 1, 2 AND 3
BODY PLANS OF ANIMALS
PASTE IN DIAGRAMSIN YOUR WORKBOOK
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THE END