Cnidarians Sandra Benito J.H., 9B

Facts

Before: Coelenterata phylum, meaning "hollow guts." Name: Cnidarians Before: Coelenterata phylum, meaning "hollow guts." Included certain ctenophores and sponges. From the Greek "cnidos," meaning "stinging nettle.“ Number of species currently existing: 10,105 species Taxonomic Classification: Domain: Eukaryota Kindom: VI. Animalia Phyla: B. Cnidaria Class: Cubozoa (Box jellies) Swimming Class: Scyphozoa (Jellyfishes) Swimming Class: Anthozoa (Anemones and corals) Sessile Class: Hydrozoa (Hydra) Both

Characteristics

Found in marine environments. Two basic body types: Polyps Medusae Tentacles Venomous cell organelles (cnidea) Gastrovascular cavity Three-layered body; epidermis, mesoglea and gastrodermis Radially symmetric Carnivorous Solitary or colonial Asexual and/or sexual reproduction Nervous system No cardiovascular system

History

Fossil history: Vendian/ Ediacaran period 650 to 540 million years ago Soft-bodied organisms Cambrian period - coral fossils Early Ordovician - more developed corals

Generalized Life Cycle And Life Expectancy

Life span is undetermined. Life cycles vary by class and species Some skip stages (e.g. Hydra) Alternation of generations (e.g. Obelia) Asexual reproduction medusae grows on external tissue Matured medusae swim away Sexual cells released Eggs are fertilized Zygote/planula settles and develops into a polyop

Digestive System

Absorb dissolved organic chemicals Filter food particles Nutrients from endosymbiotic algae Predate Crustaceans and plankton Medusae forms sink on top of the prey Gastrodem layer releases enzymes that kill the prey Cells absorb the nutrients Nutrients spread by diffusion or mobile cells Indigestible remnants are ejected

Respiratory and Circulatory System

No circulatory system No respiratory organs Absorb/expel O and CO2 into water Water in digestive cavity is expelled

Sensory System

Simple sensory system Net of nerves made of sensitive neurons Sensitive neurons are connected by chemical synapse Neuron sends neurotransmitter (chemical) to cell group

Bibliography New Oxford American Dictionary http://en.wikipedia.org/wiki/Cnidaria http://waynesword.palomar.edu/trnov01.htm#animals http://www.buzzle.com/articles/jellyfish-facts-for-kids.html http://animals.about.com/od/cnidarians/p/cnidaria.htm http://nationalzoo.si.edu/Animals/Invertebrates/Facts/cnidarians/default.cfm http://www.oceaninn.com/the-nature-preserve/cnidarians/ http://mapress.com/zootaxa/2011/f/zt03148p012.pdf http://animals.about.com/od/cnidarians/ss/cnidarians.htm http://www.ucmp.berkeley.edu/cnidaria/cnidariafr.html http://www.angelfire.com/moon2/asciencems/ http://zoology.muohio.edu/crist/Zoo312/Cnidaria.html http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20102/bio%20102%20lectures/nervous%20system/nervous1.htm