6 cnidaria
TRANSCRIPT
Dr. Parvish Pandya’s compilation
“Phylum Cnidaria”A presentation compiled from various sources by
Dr. PARVISH PANDYA,Zoology Dept. Bhavan’s College, Andheri.
Dr. Parvish Pandya’s compilation
Sites from which presentations have been downloaded and later editted. I am indeed thankful to them for their kindness and support :http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.htmlhttp://faculty.pnc.edu/jcamp/parasit/parasit.htmlhttp://www.amnh.org/rose/hope/creatinghope/http://www.biology.eku.edu/SCHUSTER/bio%20141/POWERPOINT%20NOTES/Intro%20to%20Protozoa_files/fullscreen.htmhttp://www.biosci.ohio-state.edu/~zoology/eeob405/http://www.tulane.edu/~wiser/protozoology/pwpt/http://www.iep.water.ca.gov/suisun/photos/wildlife.htmlhttp://www.uta.edu/biology/marshall/2343/http://www.uta.edu/biology/faculty/faculty.htmlhttp://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htmhttp://bio.fsu.edu/http://www.aw-bc.com/http://www.nhm.org/http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/
It is very easy to find mistakes in these presentations…..I request you to kindly rectify them and supply me the modifications needed at [email protected] a lot and have fun in teaching & learning Zoology….
Dr. Parvish Pandya’s compilation
PHYLUM CNIDARIA
THE JELLYFISH, ANEMONES AND CORALS
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Jellyfishes
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Sea Anemones
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Corals
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Phylum Cnidaria
• Coelenterata or Radiata • Differ from sponges - have rudimentary organs• have primary radial symmetry (symmetry shown
in early development and carried throughout life)
• the only other phylum that has radial symmetry is Echinodermata- which has secondary radial symmetry (ie. has bilateral symmetry in early development and later switches to radial symmetry
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MORPHOLOGY
• The cnidarian body wall has 3 basic layers – Epidermis- outer layer– Gastrodermis- lines the
gastrovascular cavity– Mesoglea- between the
two tissue layers; it is a non-cellular gelatinous layer, not a tissue
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Two Basic Body Plans
• Polyp - Sessile Forms • Medusa - Planktonic Forms
– Some species have only the polyp; a large number of species go through both stages in their life cycle
• Metagenesis- alternation of generation
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Polyp• Sessile - Polyp (hydranth or hydroid)
• Cylindrical stalk and oral end with tentacles• Mesoglea is a thin layer
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Medusa
• Free swimming -Medusa –Bell shaped–Mesoglea
constitutes bulk
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5 CellTypes
• Epithelio-muscle cells • Cover and protect • Can contract (muscular
properties) • Interstitial cells
• Production of gametes • Mucous secreting cells
(Gland cells)- mucous for attachment, feeding
• Nerve cells- irritability• Cnidocytes- protection,
predation
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How Cnidocytes Work
• On Tentacles • Defense, anchoring
and feeding
• Nematocyst• Cnidocil - trigger
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• First time • Nerve net • 2 nets
– Associated with epidermis andgastrodermis
Nervous System
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Classification
• 3 Classes • Hydrozoa• Scyphozoa • Anthozoa
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Hydrozoa• Polymorphic
• Polyp • Medusa
• Simple gastrovascularcavity - no septa
• No nematocysts in digestive cavity
• Solitary or colonial
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Composition of Colonies• 3 types of individuals • Gastrozooid -
responsible for feeding also numerousGonozooid - sexual reproductionDactylozooids - defense and food capture
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Life Cycles
• 3 basic types – Hydra - only polyp
– Asexual reproduction - budding
– Obelia - both polyp and medusa stage
– Physalia - Colony attached to float called Pneumatophore
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Life Cycle of Hydra
SEXUAL REPRODUCTION
ASEXUAL REPRODUCTION
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Physalia Life Cycle• Colony attached to a float -
pneumatophore• Individuals attached to traililng tentacles; may
be up to 9 meters long • Reproduces sexually
– Produces planula larva – Turns into medusa – Comes to surface and pneumatophore is
formed and then reproduces asexually for form colony.
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Scyphozoa(true jellyfish)
• Exclusively marine • Medusa dominant stage
•Much larger in size compared tohydrozoan medusae
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Rock Anemones