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General Zoology Unit Two Objective Eighteen
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Definitions Diploblastic – having two germ layers from which tissues and structures arise Ectoderm – outer germ layer that gives rise to tissues and structures that cover the outside Endoderm – inner germ layer that gives rise to tissues and structures that cover the inside Mesoglea – jelly-like substance found between the inner and outer layers
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Blastula Gastrulation Gastrula Ectoderm Endoderm Mesoderm Blastopore Diploblastic
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General Zoology Unit Two Objective Nineteen
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Cnidaria Eukaryotic, eumetazoans Diploblastic
Have true tissues, but no organs All are marine Radially symmetrical (no cephalization) Polymorphic – two forms (polyp & medusa) Cnidocytes – stinging cells Have a nerve net Polyps are sessile, while medusae can move Asexual and sexual reproduction
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General Zoology Unit Two Objective Twenty
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Cnidarian Taxonomy Kingdom - Animalia Phylum - Cnidaria
Class – Hydrozoa Ex. – Physalia, Obelia, Hydra, Gonionemus Class – Scyphozoa (true jellyfish) Ex. – Aurelia, Cassiopeia Class – Cubozoa Ex. – Carybdea Class – Anthozoa Ex. – Metridium, Gorgonia, Tubipora
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General Zoology Unit Two Objective Twenty One
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Cnidarian Polymorphism
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Polyp Anatomy
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Gonionemus
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Aurelia
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Cnidocyte Anatomy
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General Zoology Unit Two Objective Twenty Two
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Class - Hydrozoa Obelia Hydra Physalia
Most are marine and colonial in form Most forms exhibit alternation of generations between asexual polyps and sexual medusae, but some have only one or the other form Obelia Hydra Physalia
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Class - Scyphozoa Referred to a the true jellyfish All are solitary
Polyp stage is much reduced or absent Main body is cup shaped Aurelia
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Class - Cubozoa All are relatively small in size All are solitary
Polyp stage is much reduced Main body is cube shaped Carybdea
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Class - Anthozoa Polyp form predominant, no medusa stage
Some are solitary, while others are colonial Many form zooxanthellae relationship with algae Most ecologically important group due to reef building Metridium Gorgonia Tubipora
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General Zoology Unit Two Objective Twenty Three
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Alternation of generations
Planula Budding
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Alternation of generations
Planula Budding
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