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  1. 1. PHYLUM CNIDARIA Presented by: Gabitan, John Paulo Tero, Nariza L. Valencia, Juliet D. Zapanta, Schola Marie
  2. 2. • Radially symmetrical cnidarian body is organized as a hollow sac with the mouth and surrounding tentacles located at one end. • Based on molecular data, some systematists have proposed that cnidarians share a common ancestor with the clade of bilateral animals. • Cnidarians have two body shapes: polyp and medusa. • Polyp form, represented by hydra, typically has dorsal mouth surrounded by tentacles. • Medusa form, the mouth is located in the lower concave or oral surface; the convex upper surface is the aboral surface.
  3. 3. • Cnidarians get their name from specialized cells called cnidocytes that contain stinging organelles. • It is found mainly in epidermis especially on tentacles. • Cnidocytes contain stinging “thread capsule” called nematocysts • Cnidarians use their tentacles to capture prey and they push it into the mouth and it leads to gastrovascular cavity, where digestion takes place. • Mouth is the only opening into gastrovascular cavity that serves for both ingestion of food and expulsion of undigested material. Gas exhange and excretion occur by diffusion.
  4. 4. • Cnidarians are diploblastic meaning thay have 2 definite tissue layers. • Ectoderm which give rise to outer (covering of body) and endoderm gives rise to inner gastrodermis, which lines the gastrovascular cavity and functions in digestion. • These thin layers are separated by a thick, jellylike mesoglea, which is mainly acellular. • Cnidarians have nerve cells that form nerve nets connecting sensory cells in the body wall to contractile cells and gland cells. • Hydrostatic skeleton supports the body and allows movement.
  6. 6. HYDROZOANS HYDRA • Mainly marine but some are freshwater species • Alternation of polyp and medusa stages in most species (polyp form only in Hydra) • Some form colonies
  7. 7. SCYPHOZOANS • “True” jellyfish • Mainly marine • Typically inhabit coastal water, free swimming medusa most prominent form • Polyp stage is often reduced JELLYFISH
  8. 8. CUBOZOA BOX JELLYFISH • Inhabit tropical and subtropical waters • Have polyp stage but medusa form most prominent • Square shape when viewed from above • Actively hunt prey • Complex eyes that form blurred images
  9. 9. ANTHOZOA SEA ANEMONES • Marine • Solitary or colonial polyps • No medusa stage in most • Gatrovascular cavity divided by partitions into chamber, increasing area for digestion
  11. 11. ECONOMIC IMPORTANCE • Coral reefs (Anthozoans) serves as a habitat of fishes and this may also serve as a tourist attraction to humans. • They also provide a home for algae which creates oxygen that we breathe. The coral reefs are also important because the polyps, algae, and animals in that habitat are a major food source for other animals.