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Phylum Cnidaria THE JELLYFISH, ANEMONES AND CORALS General characteristics of phylum Cnidaria: General characteristics of phylum Cnidaria: Radial Symmetry Specialized Tissues Sensory system- nerve net Specialized cells stinging cells cnidocytes Carnivores All aquatic, mostly marine Asexual and sexual reproduction Fun Facts About 9000 species of cnidarians Oldest jellyfish, 500 million years old- found in Utah Cnidocytes Cnidocytes Stinging cells found in the tentacles Each cell has a tightly coiled, poison filed, dart-like structurenematocyst Nematocyst has a trigger haircnidocil Contact with the cnidocil causes the nematocyst to discharge Fills with water Often has barbs Tissue Structure Cells arranged into tissues- two layers Outer layer: epidermis Inner layer: gastrodermis In between layer is jelly-like: mesoglea Body Plan Radial symmetry with central mouth Tentacles surround mouth and extend from body Life Cycle Most cnidarians have 2 body forms in their life history Life Cycle Polyp- asexual and sessile Medusa- dioecious and free swimming VIDEO Birth of the Sea Nettle http://www.youtube.com/watch?v=NOf2RRmSkgQ &edufilter=Ps5lSoPViR6fXm1RM5Eu1Q Arkive – Polyp Birth, Baby Swim Overview http://www.youtube.com/watch?v=O9Bl6TQmBE0&edufilt er=Ps5lSoPViR6fXm1RM5Eu1Q / Animal Functions Feeding Circulation Respiration Excretion Response Movement Reproduction Video – Shape of Life Feeding After stinging, prey is pulled into the gastrovascular cavity Digestive chamber, 1 opening Extracellular digestion begins and nutrients are absorbed Feeding Cnidarians eat small crustaceans and fish Waste passes back out the mouth VIDEO – ARKIVE Respiration, Circulation and Excretion What do you think? Respiration, Circulation and Excretion Gastrovascular cavity brings oxygen in and waste passes out Circulation is by diffusion from one cell to the next Response - Senses Nerve net: Nerve cells that connect around the body Cnidarians can feel touch Some have cells that sense gravity or light Coordinates movement and response Movement Hydrostatic skeleton – muscles push against water filled cavities Polyps can somersault or inch along Medusa swim or float VIDEO Anemone http://www.youtube.com/watch?v=Dm98n3908QM Dance of the Jellyfish http://video.nationalgeographic.com/video/animals/invertebratesanimals/other-invertebrates/dance-jellyfish-eorg Reproduction Asexual Medusa Polyps bud from a polyp can bud other polyps Sexual External Males Eggs fertilization and females and sperm are released into the water Cnidarian Diversity Classes Hydrozoa Scyphozoa Cubozoa Anthozoa
