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Phylum Cnidaria: “stinging cell” Hollow gut- (coel) On earth- since 670 MYA radial symmetry Germ Layers: 2 epidermal (ectoderm) gastrodermal (endoderm) NO ORGAN SYSTEMS Segmentation: none Movement: sessile or motile predators Have tentacles- stinging cells (cnidocyts) , nematocysts “thread cells” used as barbs Structures: One body opening (mouth) for food to enter and wastes to exit Gastrovascular cavity: interior cavity where food is digested & nutrients are circulated around the body Nerve net: net of nerves that allow impulses to travel around the body, senses the environment Label the hydra on your notes! http://www.arkive.org/common-jellyfish/aurelia-aurita/video- Nervous: Cephalization absent; Nerve Net-conducts impulses Skeleton: Hydrostatic- water pressure maintains shape Respiration: Oxygen diffuses into body from water Digestion: mouth, GVC Excretion: simple diffusion into water Circulation: GVC- gastrovascular cavity Reproduction: asexual and sexual, alternation of generations Polyp: body with tentacles facing upward, sessile Ex: hydra, sea anenome video polyp predation Medusa: body with tentacles hanging downward, motile Ex: jellyfish Asexually: by budding Sexually: usually in medusa form, sperm and eggs are released into water (fertilized egg zygote planula larvaadult) Thousands of gametes are released at a time Video: medusa releasing from polyp Epidermis Mesoglea Gastroderm Tentacles Mesoglea Gastrovascular cavity Mouth/anus Mouth/anus Gastrovascular cavity Tentacles Medusa Polyp basal disc: sticky structure at the bottom of polyp ; sessile › Epidermis - outer covering (ectoderm) › Mesoglea - middle non-living jelly-like layer (missing mesoderm) › gastrovascular cavity (endoderm) 9 1. Hydrozoa 2. Scyphozoa 3. Anthozoa Freshwater & marine. Medusa and polyp colonies which appear to be one organism different types of polyps work together to serve the entire colony Ex: Hydra, Obelia, Gonionemus Physalia (portuguese-man-of-war) 36:40 Ocean Drifters Asexual repro.-budding. Sexual repro. via gametes 11 mouth GVC Gonad mesoglea tentacle Scyph= “cup” Large- Tentacles up to 70 meters in length All marine Independent medusa forms Lack polyp stage or have for a very short time Ex. Box jellyfish 13 ANTHO=“flower” All polyps-Medusa stage absent Solitary or colonial Some produce protective skeletons All Marine Ex. Sea anemones, corals 14 Video jewel anenome 15 Tentacles Mouth Pharynx Septum Gastrovascular cavity 16 17 Polyp secretes protective skeleton of calcium carbonate Polyp retracts when not feeding 18 19 20 21 22 23 24 Formed over thousands of years from successive layers of coral skeleton deposits The underwater equivalent of the amazon jungle- very high species diversity and biomass Reefs contain sponges, colonial hydrozoans, anemones, many varieties of coral, fish, many types of worms we’ve not discussed, not to mention bryozoans, ctenophores, protists, bacteria, etc etc.. 25 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Coral Reef Ecosystem Photo © McGraw-Hill Higher Education, Barry Barker, Photographer 26 Anthozoa Scyphozoa Cubozoa Hydrozoa Medusa cuboidal Loss of medusa Polyp stage reduced Septa divide gastrovascular cavity Radial symmetry, cnidocytes, planula larva 27 1. Cnidarians are diploblastic, what does this mean? 2. What is the mesoglea? 3. How are Hydrozoans different from other classes of cnidarians? 4. List examples of Hydrozoans. 5. What are scyphozoans, do they have a polyp stage? 6. Anthozoans are known as the ______________ animals. Give examples of anthozoans. 7. What is an anthozoan’s protective skeleton made of? 8. Why are coral reefs important? 29