Today’s Objectives: 3.4 Describe characteristics of this phylum Identify life functions of...
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Transcript of Today’s Objectives: 3.4 Describe characteristics of this phylum Identify life functions of...
Today’s Objectives: 3.4
Describe characteristics of this phylum
Identify life functions of cnidarians
Classify and give examples of phylum Cnidaria
Phylum Cnidaria
Animals with stinging cells
Characteristics of CnidariansRadial or biradial symmetryTissue-level organizationMesoglea between epidermis and
gastrodermisGastrovascular cavityNerve netCnidocytes – used for defense or
feeding
Life Functions of Cnidarians Reproduction/life cycle
– Can be monoecious or dioecious– Alternate generations between medusa
and polyp form Feeding
– Use cnidocytes to stun or kill prey– Can contract tentacles to bring to mouth– Digestion occurs in gastrovascular
cavity
Life Functions of CnidariansSupport & locomotion
–Hydrostatic skeleton–Some classes have longitudinal muscles
for movement–Medusa move by contracting bell or jet
propulsion–Some polyps can walk on tentacles,
contract, inchworm or glide on pedal disks
Reproduction in Cnidarians
Most are dioeciousPolyp can develop through budding
or from a free-swimming planula larva
Medusa almost always formed by budding from a polyp body wall
Classification of Phylum Cnidaria
Class HydrozoaClass ScyphozoaClass CubozoaClass Anthozoa
Class HydrozoaMostly marineThis is the only class with freshwater
members!Alternate generationsMostly colonial polypsOnly have cnidocytes in epidermisSperm & egg are released outside
bodyNo amoeboid cells in mesoglea
ObeliaGastrozooid – feeding polyp
formed from planula larvaeGrows through budding into more
gastrozooidsGonozooid – reproductive polyp
that forms medusa by budding Medusae then reproduce sexually
Gastrozooid
Gonozooid
GonionemusMedusa predominant - DioeciousHas a velum (not found in other
classes) which creates jet propulsion
Mouth at end of a manubrium Nerve ring in addition to nerve net
that coordinates swimming movements
Statocyst sensory structure that responds to gravity
Hydra Freshwater Polyp only, no
medusa Testes form
sperm through meiosis
Ovaries form one egg each
Young “buds” from parent until ready to survive on its own, then it drops off
Types of Locomotion in Hydra
Physalia Portuguese man-of-
war Colonial
siphonophore Does not swim, float
moved by water and wind
Long dactylozooids (tentacles) contain cnidocytes and kill prey.
Class Scyphozoa “True Jellyfish” – polyp form reduced
or absent All marine No velum Mesoglea contain amoeboid cells Cnidocytes in gastrodermis and
epidermis Gametes form in gastrodermis
Stinging nettle, Mastigias
Aurelia Extensively branched canal system Gastrodermal cells have cilia to
circulate food Feeds on plankton Rhopalium – chemosensors Statocyst – gravity sensors Lappets – touch receptors Ocelli – photoreceptors Planula develop into a scyphistoma
polyp
Aurelia
Life Cycle of Aurelia
Class Cubozoa
Medusa is cuboidal Tentacles hang from
corners Polyps reduced or absent Ex. Sea wasp
Class AnthozoaNo medusae, polyp onlyMouth has a pharynxGastrovascular cavity is divided
into sectionsMesoglea contains amoeboid
cellsSexual and asexual reproduction
Body structure of AnthozoansPedal diskOral diskSiphonoglyph – moves water
into gastrovascular cavity to maintain hydrostatic pressure.
Acontia – prevents live prey from damaging gastrovascular cavity.
Sea Anemones
Corals