sponges read H - Somma Science · 2018-01-17 · Sponges are aquatic, invertebrate animals that...

SPonges Name:_________________________________________Class:__________Date:____________

So what exactly is a sponge? Herewehaveagiantpinkbarrelspongeadornedwithtubespongesandgorgonianseafans.Howcansomethingthatlookslikethatbeconsideredananimal?Where'sthehead?Wherearethelegs?Where'sthemouth?Spongesareaquatic,invertebrateanimalsthatmakeupthephylumPorifera.ThewordPoriferameans“pore-bearing,”andahighlyporousbodyisoneofthemoststrikingfeaturesofsponges.Spongesarethesimplestmulticellularanimalsfoundinthefossilrecord.Itisdifficulttoimaginethatanorganismascomplicatedasahumanbeingcouldberelatedtosucharemarkablysimpleanimal.However,spongesrepresentanessentialstepintheevolutionofcomplexanimals:thetransitionfromsimpleprotiststomulti-celled,complexanimals.Inthisconceptwewillconsiderthecharacteristicsandclassificationofsponges,theirspecificstructuralfeatures,howtheyreproduce,andtheenvironmentsthattheyinhabit. Characteristics and Classification of Sponges ThephylumPoriferacontainsmanybeautifullycoloredspongespeciesthat

rangeinsizefromonecentimeter(aboutthewidthofapinkyfinger)tooveronemeter(aboutthearmspanofahuman)indiameter.Spongesaroseroughly500millionyearsago,andtherearecurrentlyover5,000differentspecies.Adultspongesaresessile,meaningthattheyarenotabletomovefromplacetoplace.Thischaracteristicmakesspongesseemsuperficiallyplant-like,butspongesdonotshareotherfeaturesofplants.Inparticular,spongesarenotcapableofphotosynthesis.Spongesdonothaveorgansortruetissues,however,theydohavespecializedcellsthatcancarryoutdistinctfunctionswithintheorganism.Thisisgenerallyreferredtoascellular-levelorganization.Cellspecializationisoneofthemajoradvantagesthatmulticellularanimals,ormetazoans,haveoversingle-celledorganisms.Thisisthefirststepintheevolutionoftissueandorgansystems,suchasthemuscularandnervoussystems.Thesedevelopmentsultimatelyallowhigherorganismstohavecomplexinteractionswiththeirenvironments.Therearethreeclasseswithinthephylumporifera:Calcerea,Desmospongia,andHexactinellida.Spongesaredividedintotheseclassesbasedprimarilyonthecompositionoftheirspiculesandskeletalfibers.Spiculesarerod-shapedcellularprojectionsthatmakeuptheskeletonofsponges.SpongeswithintheclassCalcereahaveskeletalspiculesmadeupofcalciumcarbonate.SpecieswithintheclassHexactinellidaarealsoreferredtoas

glassspongesbecausetheirskeletonsconsistofspiculesmadeofsilica,theprimarycomponentofglass.TheskeletonsoftheclassDesmospongiaarecomposedofspiculesmadeupofsilicaandskeletalfibersmadefromspongin,atypeofcollagenprotein.Desmospongiaisthemostabundantclassofspongesalivetoday.Morethan90%ofallknownspongespeciesarefoundwithintheclassdesmospongia.Becausetheirskeletonsareoftencomposedprimarilyofsponginfibersthatarelessrigidthanspicules,itisdesmospongiaspeciesthathavebeenusedtomakethecleaningspongeswecommonlythinkofwhenweheartheword“sponge”.

Spongesarefilter-feedersthatpumpwaterinviatheirporoussurfaceandthroughasystemofinternalcanalswherebacteriaandnutrientscanbetrappedanddigested.Summary

• Spongesarethesimplestmulticellularorganisms,classifiedbytheirprimitivecellular-leveloforganization,theirporousbodies,andtheirfilter-feedingsystem.

• Spongeshavespecializedcellsthatcancarryoutdistinctfunctionswithintheorganism.• Spongesaredividedintothreeclassesbasedprimarilyonthecompositionoftheirspiculesandskeletal

fibers.Review

1. Howmanydifferentspeciesofspongesarethere?Howaretheycharacterized?2. Howarespongesdividedintodifferentclasses?3. Whatclassofspongesismostcommon?