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