Presentation on theme: "Today’s Objectives: 3.4 Describe characteristics of this phylum"— Presentation transcript:
1Today’s Objectives: 3.4 Describe characteristics of this phylum Identify life functions of cnidariansClassify and give examples of phylum Cnidaria
2Animals with stinging cells Phylum CnidariaAnimals with stinging cells
3Characteristics of Cnidarians Radial or biradial symmetryTissue-level organizationMesoglea between epidermis and gastrodermisGastrovascular cavityNerve netCnidocytes – used for defense or feeding
4Life Functions of Cnidarians Reproduction/life cycleCan be monoecious or dioeciousAlternate generations between medusa and polyp formFeedingUse cnidocytes to stun or kill preyCan contract tentacles to bring to mouthDigestion occurs in gastrovascular cavity
5Life Functions of Cnidarians Support & locomotionHydrostatic skeletonSome classes have longitudinal muscles for movementMedusa move by contracting bell or jet propulsionSome polyps can walk on tentacles, contract, inchworm or glide on pedal disks
6Reproduction in Cnidarians Most are dioeciousPolyp can develop through budding or from a free-swimming planula larvaMedusa almost always formed by budding from a polyp body wall
7Classification of Phylum Cnidaria Class HydrozoaClass ScyphozoaClass CubozoaClass Anthozoa
8Class Hydrozoa Mostly marine This is the only class with freshwater members!Alternate generationsMostly colonial polypsOnly have cnidocytes in epidermisSperm & egg are released outside bodyNo amoeboid cells in mesoglea
9Obelia Gastrozooid – feeding polyp formed from planula larvae Grows through budding into more gastrozooidsGonozooid – reproductive polyp that forms medusa by buddingMedusae then reproduce sexually
11Gonionemus Medusa predominant - Dioecious Has a velum (not found in other classes) which creates jet propulsionMouth at end of a manubriumNerve ring in addition to nerve net that coordinates swimming movementsStatocyst sensory structure that responds to gravity
19Aurelia Extensively branched canal system Gastrodermal cells have cilia to circulate foodFeeds on planktonRhopalium – chemosensorsStatocyst – gravity sensorsLappets – touch receptorsOcelli – photoreceptorsPlanula develop into a scyphistoma polyp
22Class Cubozoa Medusa is cuboidal Tentacles hang from corners Polyps reduced or absentEx. Sea waspClass CubozoaVenom from one individual can kill 60 adults.Takes 30 seconds to 4 minutes to kill.
23Class Anthozoa No medusae, polyp only Mouth has a pharynx Gastrovascular cavity is divided into sectionsMesoglea contains amoeboid cellsSexual and asexual reproduction
24Body structure of Anthozoans Pedal diskOral diskSiphonoglyph – moves water into gastrovascular cavity to maintain hydrostatic pressure.Acontia – prevents live prey from damaging gastrovascular cavity.