 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! 10.html

 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 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 larva  adult)  Thousands of gametes are released at a time

Video: medusa releasing from polyp

basal disc: sticky structure at the bottom of polyp ; sessile Epidermis Mesoglea Gastroderm Mesoglea Gastrovascular cavity Mouth/anus Tentacles Mouth/anus Gastrovascular cavity Polyp Medusa

› 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  E x: Hydra, Obelia, GonionemusHydra Physalia ( portuguese-man-of-war) 36:40 Ocean Drifters  Asexual repro.-budding.  Sexual repro. via gametes 11

 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 12

 ANTHO=“flower”  All polyps-Medusa stage absent  Solitary or colonial  Some produce protective skeletons  All Marine  Ex. Sea anemones, corals 13

14 Video jewel anenome

15 MouthMouth TentaclesTentacles PharynxPharynx SeptumSeptum Gastrovascular cavity

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 Protective skeleton of calcium carbonate  Polyp retracts when not feeding 17

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 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.. 24

25 Coral Reef Ecosystem Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Photo © McGraw-Hill Higher Education, Barry Barker, Photographer

26 Anthozoa ScyphozoaCubozoa Hydrozoa Radial symmetry, cnidocytes, planula larva Septa divide gastrovascular cavity Medusa cuboidal Polyp stage reduced Loss of medusa

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 ?

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