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Phylum Cnidaria (Coelenterata)

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Presentation on theme: "Phylum Cnidaria (Coelenterata)"— Presentation transcript:

1 Phylum Cnidaria (Coelenterata)
Kingdom Animalia Phylum Cnidaria (Coelenterata)

2 Two Body Forms Cnidarians include: Jellyfish, Sea Anemones, Hydras, and Corals All have radial symmetry (“little rings”) Two body forms: Medusa- Free-floating, jelly-like and often umbrella shaped Polyp- Tubelike and usually attached to a rock or other surface

3 Two Body Forms Tentacles surround mouth, located at free end of body
Three layers of cells: Outer layer from ectoderm Inner layer from endoderm Middle layer of mesoglea (jelly-like) Cells arranged into tissues Coelenteron- digestive cavity where enzymes digest food

4 Two Body Forms

5 Body Forms Extracellular digestion Cnidocytes
Stinging cells located on the tentacles Distinguishing characteristic of Cnidarians Small, barbed harpoon (nematocyst) within each Cnidocyte Used for defense or to spear prey Toxins can be deadly or only stun Extracellular digestion Digestion begins outside the cell in the gastrovascular cavity Enzymes break food into smaller fragments Cells lining cavity engulf fragments and finish digestion intracellularly

6 Class Hydrozoa Freshwater hydrozoa
Genus Hydra exist only as Polyps less than .4” long Attach to objects with sticky secretion from the basal disk Can glide on objects or tumble Have a nerve net- branching system of nerves with no brain

7 Class Hydrozoa Marine Hydrozoa Often live in colonies
Can be medusas or polyps Ex: Portuguese man-of-war Physalia- floats on water and dangles tentacles with powerful neurotoxins (nerve poisons)

8 Reproduction in Hydrozoa
Most hydrozoans are colonial and reproduce asexually by budding Some species are sexual Most single sexes, but some hermaphrodites Genus Obelia Colonize a single polyp with buds Reproductive polyps produce medusas Medusas reproduce sexually and produce ciliated larvae called planulae, which develop into new polyps

9 Obelia Reproduction

10 Class Scyphozoa True jellyfish and active predators
Jellyfish relatives: Cubozoans- Small box-shaped medusas with tentacles on corner of “box” Inconspicuous polyp stage Ex: Box jellysish or Sea wasp can be deadly Phylum Ctenophora- Comb jellies have only a medusa stage and no nematocysts Class Tenaculata- with tentacles Class Nuda- without tentacles Irukandji Jellyfish (Carukua barnesi) 2.5 cm in diameter Kills in days True jellyfish and active predators Range from thimble size to queen-size mattresses Mostly medusas which reproduce sexually Polyp stages early in life

11 Jellyfish Relatives

12 Class Anthozoa Some reproduce asexually by budding
Largest class existing only as polyps Includes anemones, coral, sea pansies, sea fans, and sea whips Nearly all contain symbiotic algae, dinoflagellates, in exchange for food Many of the brilliant colors come from the algae Some reproduce asexually by budding Others sexual with sperm and egg being released into the ocean where fertilization occurs Zygotes develop into planulae that settle and develop into polyps

13 Class Anthozoa

14 Class Anthozoa Sea anemones- Small and colorful in coastal areas
Highly muscular- can retract when touched Reproduce asexually by splitting themselves into two Corals Colonies called reefs Secrete calcium carbonate skeleton that cements to skeletons of neighbors Top layer is living polyps Bottom layers are old skeletons

15 Great Barrier Reef

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