1. 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

2. Forms of Cnidarians

3. 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

4. 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

6. 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

7. Class Hydrozoa: The Hydras • Polyp phase is dominant • Generally microscopic • Generally freshwater

8. 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

9. 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

10. Coral Reefs Clownfish living in An anemone