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Cnidaria Daniel Lee Matt Reynolds Hussain Parbtani Period 5 General Characteristics Live in exclusively aquatic or marine environments Unique feature of cnidocyte (exclusive to cnidarians) Located on epidermis, usually on the tentacles of the cnidarian Contains cnidea in the form of nematocysts, spirocysts, or ptychocysts Nematocysts – capsules of coiled threads and barbs (stylets). When discharged deliver a venom to paralyze victim so it can be ingested Spirocysts – found in corals/anemones. Sticky threads to help cnidarian capture and stick to prey’s surface Ptychocysts – usually found in bottom dwellers. Injected to help establish a firm hold Hollow sac-like body. Either vase shaped (polyp) or bell shaped (medusa) Cells specialized into tissues One body opening (gastrovascular cavity) Tentacles Mucus secreting cells give the cnidarian a slimy characteristic Class - Anthozoa Coral Works cited: http://en.wikipedia.org/wiki/Coral Class - Cubozoa Box Jellyfish Works cited: http://worldofthestrange.co.uk/blog/media/1/box-jellyfish-22916-sw.jpg Class - Hydrozoa Hydra Works cited: http://en.wikipedia.org/wiki/Hydra_(genus) Works cited: http://www.animalpicturesarchive.com/ArchOLD-7/1192670344.jpg Class - Scyphozoa True Jellyfish Body Plan • Cnidarians are the simplest organisms that have attained a tissue level of organization. • They consist of layers with an epidermis, an inner gastrodermis, and a non-cellular mesoglea between the two. • The mouth/anus serves as the entrance and exit to and from the gastrovascular cavity. • Cnidarians are radially symmetrical, meaning that it would look the same if it were cut in half vertically in any direction. http://biology.unm.edu/ccouncil/Biology_203/Im ages/SimpleAnimals/cnidariaDiagram.jpeg Works Cited: http://cas.bellarmine.edu/tietjen/images/cnidarians.htm http://animals.about.com/od/cnidarians/ss/cnidarians_2.htm Feeding • Cnidarians are mostly carnivorous and eat small crustaceans and fish. • They obtain their food by waiting for prey to drift by and then latch onto it with their tentacles and paralyzing the food with its nematocysts. • After the prey is paralyzed, it is pulled through the mouth into the gastrovascular cavity where it is digested by beating flagella lining the cavity and enzymes http://baynature.org/articles/jul-sep-2006/from-collecting-torecollecting/v06n03_404.jpg/image_listlarge Works Cited: http://animals.about.com/od/cnidarians/ss/cnidar ians_6.htm Respiration • Cnidarians don’t have any lungs or gills. • They acquire oxygen through diffusion. • Cells of cnidarians are extremely thin, so the oxygen in the water can easily pass through all of the cells in the organism. • Most cnidarians are tiny and/or thin so that they can distribute the gases throughout their bodies • Diffusion between the organism and the water occurs in the epidermis and gastrodermis Works Cited: http://www.palaeos.com/Invertebr ates/Cnidaria/Cnidaria.htm http://photography.nationalgeographic.com/staticfiles/NGS/Shared/Static Files/Photography/Images/Content/crown-jellyfish-newbert-1145563ga.jpg Circulation • As with respiration, circulation occurs through diffusion in cnidarians. • They don’t have any circulatory organs you see in other animals, such as a heart or blood vessels. • They receive their nutrients and gases responsible of circulation through the water directly by diffusion inside of the gastrovascular cavity http://oceanexplorer.noaa.gov/explorations/02fire/logs/jul26/media/cnidar ian_600.jpg Works Cited: http://faculty.clintoncc.suny.edu/fa culty/michael.gregory/files/Bio%20 102/Bio%20102%20lectures/Circu latory%20System/circulat.htm Reproduction Cnidarians can go through both asexual and sexual reproduction. Asexual reproduction is relatively fast, and the end result is an exact genetically identical clone. Asexual Production is often characteristic of favorable conditions such as in the spring and in the summer. Compared to asexual reproduction, sexual reproduction is cnidarians is relatively slow. It usually is characteristic of decline conditions such as the fall season, and it results in a genetically dissimilar offspring. Work cited: http://www.cbu.edu/~seisen/Cnidaria/sld0 11.htm Excretion Like Respiration, Cnidarians also achieve excretion through the process of Diffusion. Once the nutrients are absorbed, they reach the outer cell layer through diffusion. Parts of a prey that are indigestible, are disposed of through the mouth. Ammonia is the main waste product of the cells, and is removed by external and internal water currents. Work cited: universe-review.ca/R10-33-anatomy.htm Movements Most adult Cnidarians are free floating. In the larval Stage, Cnidarians are free swimming. Cnidarians use jet propulsion by sucking water into the grastrovascular cavity and then spitting it out in a strong spurt of water to move themselves. Their tissues are very thin, and the lack of muscles is the reason they use jet propulsion. Work cited: http://en.wikipedia.org/wiki/Cnidaria Response Cnidarians have no brain or central nervous system. They consists of a decentralized nerve nets, which consist of sensory neurons. These neurons cause muscle reaction, each time a stimuli is presented. For example, a certain “smell” might cause muscle contraction. Most of the communication between nerve cells are via chemical synapses. Work cited: cnidariag.blogspot.com/2007_02_01_archive.html Works Cited Klappenbach, Laura. "Radial Symmetry - Radial Symmetry in Cnidarians." Animals Wildlife - Animal Facts, Animal Pictures, Habitat Facts, Evolution and Zoology. About.com. Web. 15 Apr. 2010. <http://animals.about.com/od/cnidarians/ss/cnidarians_2.htm>. Klappenbach, Laura. "Diet - Cnidarian Diet and Eating Habits." Animals Wildlife - Animal Facts, Animal Pictures, Habitat Facts, Evolution and Zoology. About.com. Web. 16 Apr. 2010. <http://animals.about.com/od/cnidarians/ss/cnidarians_6.htm>. "Invertebrates: Cnidaria: Cnidaria." Palaeos. Web. 20 Apr. 2010. <http://www.palaeos.com/Invertebrates/Cnidaria/Cnidaria.htm>. "Circulatory System." Clinton Community College. Web. 20 Apr. 2010. <http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20102/Bio%20102%20lectures/Circulatory%20 System/circulat.htm>. Klappenbach, Laura. "Cnidocytes - Cnidocyte Organelles in Cnidarians." Animals Wildlife - Animal Facts, Animal Pictures, Habitat Facts, Evolution and Zoology. Web. 16 Apr. 2010. <http://animals.about.com/od/cnidarians/ss/cnidarians_5.htm>. "Characteristics of Cnidarians |." The Most Beautiful Butterflies In The World | |. Web. 16 Apr. 2010. <http://www.butterflyrevolt.com/characteristics-of-cnidarians.html>. "Cnidarians." W. Fielding Rubel School of Business: Bellarmine University. Web. 16 Apr. 2010. <http://cas.bellarmine.edu/tietjen/images/cnidarians.htm>.