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Phylum Cnidaria. Cnidarians Include Hydras, jellyfish, sea anemones & corals Radially symmetrical Acoelomate Two basic forms: Polyp : Cylindrical form which attach bases to substratum Medusa : Flattened, mouth down version of the polyp. Moves freely. Forms of Cnidarians. Body Plan.
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Phylum Cnidaria Cnidarians Include Hydras, jellyfish, sea anemones & corals Radially symmetrical Acoelomate Two basic forms: Polyp: Cylindrical form which attach bases to substratum Medusa: Flattened, mouth down version of the polyp. Moves freely
Body Plan • Basic Body Plan: • Has an outer epidermis • Has an inner gastrodermis which forms a gastrovascular cavity • Has a middle "jelly filled" layer called mesoglea
Cnidocytes • Cnidarians are predators which have tentacles possessing batteries of special cells called Cnidocytes • Cnidocytes contain special stining capsules called nematocysts. • When triggered, these cells shoot out a discharge thread which can entangle and/or poison it's intended prey
Reproduction • Reproduction can occur sexually by fertilization of egg and sperm forming larvae. • Reproduction can also occur asexually through budding • 3 Major classes • Class Hydrozoa: Hydras • Class Scyphozoa: Jellyfish • Class Anthozoa: Anemones and corals
Class Hydrozoa: The Hydras • Polyp phase is dominant • Generally microscopic • Generally freshwater
Class Scyphozoa: The Jellies • Generally refered tro as jellies • Medusa stage is dominant • Come in a variety of forms • Aggressive predators, and can be dangerous to humans Jelly Portugese Man-o-war
Class Anthozoa: Anemones & Corals • Appear like plants but are animals. • Polyp form is dominant. • Corals build calcium shells to protect themselves • Have symbiotic relationship with algae. • Can build extensive masses which can form land masses. Anemone Coral Polyps
Coral Reefs Clownfish living in An anemone