CnidariaSlide 2Slide 3Nerve netSlide 5Cnidaria: digestionCnidaria: Body wallSlide 8EpidermisGastrodermisSlide 11Body formsPolyp and medusaSlide 14Slide 15Slide 16CnidocytesSlide 18Slide 19Slide 20Slide 21Movement of medusaeYoutube videos Mudusae in aquariaPolypsYoutube AnemonesLife CyclesSlide 27Slide 28Slide 29Classes of CnidariaHydrozoaSlide 32Colonial HydrozoaSlide 34Slide 35Slide 36Slide 37Colonial Hydrozoa: PhysaliaSlide 39Slide 40ScyphozoaSlide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49CubozoaSlide 51Slide 52Slide 53Box jellyfish videoAnthozoaSlide 56Anthozoa: Zoantharia: sea anemones and hard coralsSlide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Slide 66Slide 67Anthozoa: OctocoralliaSlide 69Slide 70Slide 71Slide 72Slide 73Soft coralsSlide 75Slide 76Slide 77Coral ReefsSlide 79Slide 80Slide 81Slide 82Types of Coral ReefsSlide 84Slide 85Slide 86Slide 87Slide 88Coral Reef ZonationSlide 90Slide 91Coral Reef DiversitySlide 93Slide 94Slide 95Slide 96Slide 97Slide 98Slide 99Threats to coral reefsSlide 101Slide 102Youtube corals reefsSlide 104Phylum CtenophoraSlide 106Slide 107Slide 108Slide 109Slide 110Slide 111Slide 112Slide 113Ctenophore video clipsCnidariaCnidariaCnidariaCnidariaThe phylum Cnidaria includes over The phylum Cnidaria includes over 9,000 species of aquatic, radially 9,000 species of aquatic, radially symmetrical animals which have symmetrical animals which have specialized stinging organelles called specialized stinging organelles called nematocysts.nematocysts.They include the jellyfish, box jellyfish, They include the jellyfish, box jellyfish, sea anemones, fire corals, sea pens sea anemones, fire corals, sea pens and hard corals.and hard corals.CnidariaCnidariaCnidarians are diploblastic having Cnidarians are diploblastic having only two well-defined germ layers only two well-defined germ layers (ectoderm and endoderm).(ectoderm and endoderm).Cnidarians are the simplest animals Cnidarians are the simplest animals equipped with nerve cells which are equipped with nerve cells which are arranged into a nerve net, but there arranged into a nerve net, but there is no central nervous system. is no central nervous system.Nerve netNerve netThe nerve net is a diffuse nervous system. The nerve net is a diffuse nervous system. Nerve impulses are transmitted between Nerve impulses are transmitted between cells by the release of neurotransmitters cells by the release of neurotransmitters from vesicles, which carry the signal across from vesicles, which carry the signal across the synapse (gap) between cells.the synapse (gap) between cells.Unlike “higher animals” impulses can travel Unlike “higher animals” impulses can travel in both directions along a nerve because in both directions along a nerve because many synapses have vesicles on both sides. many synapses have vesicles on both sides.Nerve netNerve netIn cnidarians there is no brain, but in some In cnidarians there is no brain, but in some medusae there are multiple nerve nets. medusae there are multiple nerve nets. For example, in Scyphozoan jellyfish there For example, in Scyphozoan jellyfish there is a fast-conducting nerve net for is a fast-conducting nerve net for coordinating swimming movements and a coordinating swimming movements and a slower net to coordinate movements of slower net to coordinate movements of tentacles.tentacles.Cnidaria: digestionCnidaria: digestionCnidarians have an internal body Cnidarians have an internal body cavity, the gastrovascular cavity, but cavity, the gastrovascular cavity, but no one-way gut. Food enters and no one-way gut. Food enters and waste exits through the same waste exits through the same opening, the oral cavity.opening, the oral cavity.Digestion takes place extracellularly Digestion takes place extracellularly within the gastrovascular cavity.within the gastrovascular cavity.Cnidaria: Body wallCnidaria: Body wallThe body wall that surrounds the The body wall that surrounds the gastrovascular cavity has an outer gastrovascular cavity has an outer epidermis and an inner gastrodermis.epidermis and an inner gastrodermis.In between these two layers is a In between these two layers is a gelatinous layer of mesoglea, which gelatinous layer of mesoglea, which may contain elastic fibers or be may contain elastic fibers or be stiffened with spicules or flexible stiffened with spicules or flexible proteins. proteins.Fig. 7.2Figure 13.02EpidermisEpidermisThe epidermis contains a variety of The epidermis contains a variety of different cells including mucus secreting different cells including mucus secreting gland cells, cnidocytes (stinging cells), gland cells, cnidocytes (stinging cells), sensory, nerve and epitheliomuscular cells.sensory, nerve and epitheliomuscular cells.Epitheliomuscular cells contain myofibrils Epitheliomuscular cells contain myofibrils and together these form a layer of and together these form a layer of longitudinal muscle that can be contracted longitudinal muscle that can be contracted to shorten the body or tentacles.to shorten the body or tentacles.GastrodermisGastrodermisThe gastrodermis consists mainly of The gastrodermis consists mainly of nutritive-muscular cells that contain nutritive-muscular cells that contain many food vacuoles for digestion and many food vacuoles for digestion and also myofibrils that connect to form a also myofibrils that connect to form a circular muscle layer.circular muscle layer.There are also gland cells that There are also gland cells that secrete digestive enzymes.secrete digestive enzymes.Figure 7.3Figure 13.03Body formsBody formsCnidaria have one of two basic body Cnidaria have one of two basic body forms forms Polyp Polyp Medusa Medusa In some groups one or other body In some groups one or other body form is used exclusively, but in others form is used exclusively, but in others the two forms are used in a single life the two forms are used in a single life cycle. cycle.Polyp and medusaPolyp and medusaThe polyp or hydroid form is adapted The polyp or hydroid form is adapted to a sessile existence and the medusa to a sessile existence and the medusa form to a free-floating or pelagic life.form to a free-floating or pelagic life.In both cases radial symmetry is In both cases radial symmetry is favored because stimuli and food are favored because stimuli and food are equally likely to come from all equally