SPonges Name: _________________________________________ Class:__________ Date: ____________ So what exactly is a sponge? Here we have a giant pink barrel sponge adorned with tube sponges and gorgonian sea fans. How can something that looks like that be considered an animal? Where's the head? Where are the legs? Where's the mouth? Sponges are aquatic, invertebrate animals that make up the phylum Porifera. The word Porifera means “pore-bearing,” and a highly porous body is one of the most striking features of sponges. Sponges are the simplest multicellular animals found in the fossil record. It is difficult to imagine that an organism as complicated as a human being could be related to such a remarkably simple animal. However, sponges represent an essential step in the evolution of complex animals: the transition from simple protists to multi-celled, complex animals. In this concept we will consider the characteristics and classification of sponges, their specific structural features, how they reproduce, and the environments that they inhabit. Characteristics and Classification of Sponges The phylum Porifera contains many beautifully colored sponge species that range in size from one centimeter (about the width of a pinky finger) to over one meter (about the arm span of a human) in diameter. Sponges arose roughly 500 million years ago, and there are currently over 5,000 different species. Adult sponges are sessile, meaning that they are not able to move from place to place. This characteristic makes sponges seem superficially plant-like, but sponges do not share other features of plants. In particular, sponges are not capable of photosynthesis. Sponges do not have organs or true tissues, however, they do have specialized cells that can carry out distinct functions within the organism. This is generally referred to as cellular-level organization. Cell specialization is one of the major advantages that multicellular animals, or metazoans, have over single-celled organisms. This is the first step in the evolution of tissue and organ systems, such as the muscular and nervous systems. These developments ultimately allow higher organisms to have complex interactions with their environments. There are three classes within the phylum porifera: Calcerea, Desmospongia, and Hexactinellida. Sponges are divided into these classes based primarily on the composition of their spicules and skeletal fibers. Spicules are rod-shaped cellular projections that make up the skeleton of sponges. Sponges within the class Calcerea have skeletal spicules made up of calcium carbonate. Species within the class Hexactinellida are also referred to as glass sponges because their skeletons consist of spicules made of silica, the primary component of glass. The skeletons of the class Desmospongia are composed of spicules made up of silica and skeletal fibers made from spongin, a type of collagen protein. Desmospongia is the most abundant class of sponges alive today. More than 90% of all known sponge species are found within the class desmospongia. Because their skeletons are often composed primarily of spongin fibers that are less rigid than spicules, it is desmospongia species that have been used to make the cleaning sponges we commonly think of when we hear the word “sponge”.

sponges read H - Somma Science · 2018-01-17 · Sponges are aquatic, invertebrate animals that make up the phylum Porifera. The word Porifera means “pore-bearing,” and a highly

Download PDF Report

Upload
others
View
2
Download
0

Embed Size (px)

Citation preview

Page 1: sponges read H - Somma Science · 2018-01-17 · Sponges are aquatic, invertebrate animals that make up the phylum Porifera. The word Porifera means “pore-bearing,” and a highly

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”.

Page 2: sponges read H - Somma Science · 2018-01-17 · Sponges are aquatic, invertebrate animals that make up the phylum Porifera. The word Porifera means “pore-bearing,” and a highly

Spongesarefilter-feedersthatpumpwaterinviatheirporoussurfaceandthroughasystemofinternalcanalswherebacteriaandnutrientscanbetrappedanddigested.Summary

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

• Spongeshavespecializedcellsthatcancarryoutdistinctfunctionswithintheorganism.• Spongesaredividedintothreeclassesbasedprimarilyonthecompositionoftheirspiculesandskeletal

fibers.Review

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