CnidariansSandra Benito J.H., 9B

Facts

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:

PolypsMedusae

TentaclesVenomous cell organelles (cnidea)Gastrovascular cavityThree-layered body; epidermis, mesoglea and gastrodermisRadially symmetricCarnivorousSolitary or colonialAsexual and/or sexual reproductionNervous systemNo 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 CycleAnd 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 tissueMatured medusae swim awaySexual cells releasedEggs are fertilizedZygote/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 andCirculatory System

No circulatory systemNo respiratory organs

Absorb/expel O and CO2 into water

Water in digestive cavity is expelled

Sensory System

Simple sensory systemNet of nerves made of

sensitive neuronsSensitive neurons are

connected by chemical synapse

Neuron sends neurotransmitter (chemical) to cell group

BibliographyNew Oxford American Dictionaryhttp://en.wikipedia.org/wiki/Cnidariahttp://waynesword.palomar.edu/trnov01.htm#animalshttp://www.buzzle.com/articles/jellyfish-facts-for-kids.htmlhttp://animals.about.com/od/cnidarians/p/cnidaria.htmhttp://nationalzoo.si.edu/Animals/Invertebrates/Facts/cnidarians/default.cfmhttp://www.oceaninn.com/the-nature-preserve/cnidarians/http://mapress.com/zootaxa/2011/f/zt03148p012.pdfhttp://animals.about.com/od/cnidarians/ss/cnidarians.htmhttp://www.ucmp.berkeley.edu/cnidaria/cnidariafr.htmlhttp://www.angelfire.com/moon2/asciencems/http://zoology.muohio.edu/crist/Zoo312/Cnidaria.htmlhttp://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20102/bio

%20102%20lectures/nervous%20system/nervous1.htm