Transcript Cnidaria - Net Start Class

Cnidaria
General Characteristics
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The name Cnidaria comes from the Greek word "cnidos," which
means stinging nettle
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An exclusively aquatic phylum
Tissue level organization
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They have stinging cells called nematocysts
Generally, their bodies are two cell layers thick
Radial symmetry; Little specialization; Pseudocoelomate
Extracellular digestion
Hydrostatic skeleton
Both asexual and sexual reproduction
External fertilization
One opening, the mouth
http://fotokudra.lt/files/I261542.jpg
Class Hydrozoa (Hydroids)
Hydra
http://kentsimmons.uwinnipeg.ca/1
6cm05/16labman05/lb5pg3_files/h
ydra3.jpg
Obelia
http://www.wallawalla.edu/academics/departments/b
iology/rosario/inverts/Cnidaria/ClassHydrozoa/HydroidPolyps/Obelia_dichotoma.html
Goneonemus
http://www.biology.iastate.edu/Courses
/211L/Cnidar/%20CnidINDX.htm
Class Scyphozoa (Jellyfish)
Aurelia
http://seanet.stanford.edu/HydroScyphozoa/aurelia_lab580.jpg
Class Anthozoa (Corals & Sea Anemone)
Sea Anemone
http://www.valdosta.edu/~jlgoble/Sea%20Anemone%20Diadumene%20Dia%2030c
m%201.JPG
Class Cubomedusa (Box Jellyfish)
Box Jelly
http://thestashbox.files.wordpress.com/2009/02/226boxjellyfish1.jpg
Body Plan
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Tissue level of organization
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Outer covering (epidermis), inner gasterodermis, non-cellular mesoglea
between the two; Diploblastic, body and tentacles consists of two cell layers
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Possess stinging structures, nematocysts, housed in cells called
cnidocytes; Single body opening, the mouth
Radial symmetry
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Two body forms
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Polyp: cylindrical with tentacles at one end; Sessile (non-motile) but some
capable of locomotion; mouth points upward; EX: The Hydra
Medusa: Free swimming; Bell shaped; Swim by undulations of their bell;
Thicker mesoglea mouth-side down; EX: The Jellyfish
Some cnidarians exist only in polypoid or medusoid form, others
alternate between the two
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Both diploid so not true alternation of generations
Body Plan cont.
http://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/cnidariaDiagram.jpeg
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Carnivorous or filter feeders
Medusa do not hunt for prey, use “sit-and-trap” method
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Uses cnidae and toxins to stun and kill prey
Sessile ployps depend on organisms that come in contact with
tentacles
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http://www.nick.com/multimedia/binits08
games/spongebob-jellyfishin-game.png
Feeding
Tentacles have stinging cells (cnidocytes) that contain small harpoons called
nematocysts
Harpoon propelled by osmotic pressure, spears prey and draws it back to
hydra
Both have a ring of tentacles around the mouth
Extracellular digestion; gut cavity for digestion, lining cells
engulf food by phagocytosis
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Enzymes secreted from the gastrodermis break down the food
http://www.arcodiv.org/cnidarians.html
Respiration
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Contains no respiratory system
This image depicts the internal
structure of a jellyfish (a
Medusae cnidaria). Because the
great majority of cells are directly
in contact with the ocean water,
a complicated respiratory system
is not needed.
http://www.arcodiv.org/cnidarians.html
Circulation
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No circulatory system (blood vessels)
Majority of cells come in direct contact of seawater
Have gastrovascular cavity; inner cells exposed to water
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Only two cell layers thick, all cells exposed to water for nutrient and gas
exchange
http://www.connecticutvalleybiological.com/images/vc1336v.jpg
Excretion
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Contains no excretory organs
Gastrovascular cavity serves for gas exchange and digestion
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Gas exchange takes place directly across the surface of their body and
waste is released either through their gastrovascular cavity or by diffusion
through their skin
No anus
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Excretes through mouth, only opening
http://www.arcodiv.org/cnidarians.html
Response
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Simple net like nervous system
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Coordinates contraction of muscles; Little central control
http://www.arcodiv.org/cnidarians.html
http://www.aboutmyplanet.com/files/2008/12/800pxJellyfish_in_the_Montery_Bay_Aquarium-resized.jpg
Movement
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Polyp
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Sits on basal disk, used to glide around with help of mucus
secretions
Some can somersault, bending over and attaching itself to
substrate by its tentacles and looping over to new location
If polyp detaches itself from substrate, it can float to surface
Medusae
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Outer layer, epithelium, contains specialized epitheliomuscular cells,
each can contract individually
These cells form muscular rings around the bell shape of the
jellyfish; allows the animal to propel through water
Reproduction
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Polyps reproduce asexually (budding and fragmentation)
Medusae reproduce sexually
Fertilization external
Alternation between medusa, sexually reproductive stage, and
polyp, the asexual stage
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Class Anthozoa has no medusa stage
Medusae has a distinct larval stage which is planktonic; called
planulae; multicellular, pear-shaped, entirely ciliated
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Jellyfish have separate male and females
Medusae stage is dominant
Some exhibit the medusa form throughout their life while others first pass
through other phases before maturing into the medusa form
Reproduction
http://universe-review.ca/I10-82-cnidaria.jpg
Works Cited
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"Introduction to Cnidaria." UCMP - University of California Museum of Paleontology. Web. 15 Apr. 2010.
<http://www.ucmp.berkeley.edu/cnidaria/cnidaria.html>.
"Cnidarians." W. Fielding Rubel School of Business: Bellarmine University. Web. 16 Apr. 2010.
<http://cas.bellarmine.edu/tietjen/images/cnidarians.htm>.
"The Anemones, Corals and Jellyfish (Phylum Cnidaria)." The Earth Life Web. Web. 19 Apr. 2010.
<http://www.earthlife.net/inverts/cnidaria.html>.
Klappenbach, Laura. "Diet - Cnidarian Diet and Eating Habits." Animals Wildlife - Animal Facts, Animal
Pictures, Habitat Facts, Evolution and Zoology. Web. 20 Apr. 2010.
<http://animals.about.com/od/cnidarians/ss/cnidarians_6.htm>.
"The Noncoelomate Animals." Biology. Sixth ed. Boston: McGraw Hill, 2002. 886-89. Print.
Works Cited (Pictures)
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"Multi-cell Organisms." A Review of the Universe. Web. 16 Apr. 2010. <http://universe-review.ca/F10multicell.htm#Index>.
"Simple Animals." Web. 19 Apr. 2010.
<http://biology.unm.edu/ccouncil/Biology_203/Summaries/SimpleAnimals.htm>.
"New Page 1." Virtual Microscope Home Page. Web. 19 Apr. 2010.
<http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb5pg3.htm>.
"Obelia Dichotoma." WWU: On Campus. Web. 19 Apr. 2010.
<http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Cnidaria/ClassHydrozoa/HydroidPolyps/Obelia_dichotoma.html>.
"Gonionemus." Biology Program at ISU. Web. 19 Apr. 2010.
<http://www.biology.iastate.edu/Courses/211L/Cnidar/%20CnidINDX.htm>.
"Hydrozoa & Scyphozoa." SeaNet. Web. 19 Apr. 2010.
<http://seanet.stanford.edu/HydroScyphozoa/index.html>.
"Search Results | SpongeBob.com." SpongeBob.com | SpongeBob SquarePants Episodes, Games, & Pictures.
Web. 20 Apr. 2010. <http://spongebob.nick.com/search/game/spongebob%20games/0>.
"Anemone." Valdosta State University. Web. 19 Apr. 2010. <http://www.valdosta.edu/~jlgoble/topic.html>.
"Foto KÅ«dra - Fotografija - Cnidaria Scyphozoa II." FotoKÅ«dra - Fotografija | KÅ«ryba | Bendravimas. Web.
20 Apr. 2010. <http://fotokudra.lt/img.php?img=182032&nav=cat&page=156>.
"Jellyfish Take Over Ocean: A Dangerous Warning Sign." Go Green. Web. 20 Apr. 2010.
<http://www.aboutmyplanet.com/green-news/jellyfish-ocean/>.
Hopcroft, Russ. "Cnidarians - Jellyfish and Kin." Arctic Ocean Diversity. Census of Marine Life, 4 Jan. 2008.
Web. 20 Apr. 2010. <http://www.arcodiv.org/cnidarians.html>