marine conservation science & policy: cartilaginous …...while most sharks live between 20 and...
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MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.1
FocusQuestionWhat are cartilaginous fish?What features differentiate them andwhere are their habitats?Howdohumansaffectthemandwhyaretheyimportant?
ObjectivesStudents will research the cartilaginous fish class and their defining characteristics. Studentswilllearnto:
• Identifythedefiningfeaturesofthecartilaginousfish.• Explainwhatresourcestheydependonandwheretheycanbefound.• Demonstrateknowledgebyresearchingandpresentingaspeciesofcartilaginousfish.
Studentwilldiscusshowtheseorganismscanbeprotectedforfuturegenerations.Thiswillbeaproject-basedactivitywherestudentswilldissectadogfish.
BackgroundThecartilaginousfishclass,orChondrichthyes,isdefinedbyoneparticularfeature:a
skeletonmade of cartilage, a dense, rubberymaterial that is lighter andmore flexible thanbone.Thisclassencompassesallsharks,raysandskates,aswellassawfishandchimaeras.Allmodern Chondrichthyes are thought to have evolved from acanthodians almost 400 millionyears ago, fromwhich they retained a few common characteristics, including their skeleton.Becauseofthiscartilage,thespeciesinthisclassdonothavebonemarrow,sotheirredbloodcells,essentialfordeliveringoxygenthroughoutthebody,areproducedinthespleen.
Asidefrombeingjawedvertebrates,allChondrichthyesalsosharepairednostrils,gills,scales, and a multi-chambered heart. Unlike fish, these species have no swim bladder. Therespiratory systemoftheseorganisms reliesuponfivetosevengillpairsontheundersideorside of the head, which extract oxygen as water passes through them. Some species mustremainmoving inorder tokeepwater flowing through their gills,whileothershaveadaptedactive-pumpingspiracles.Thespiracleallowsspecieslikethenursesharktorest,whilethreshersharksandmackerelsharksnolongerhavethemandmustmaintainmotion.
The scalesof these speciesare calleddermaldenticles andarephysically similar torowsoftinyteeth,givingtheirskinthedistinct sandpaper-liketexturethatbothprotectsandstreamlines.Thescalesofbonyfishgrowinsize,whilethoseoftheChondrichthyesclassformnewscalesinnewspacesasthebodygrows.Otherfeaturesofthesespecies,suchasthenoseofsawfishesandthespinesofstingrays,arealsostructurallymodifiedscales.Ratherthanbeingfirmlyattachedtotheirjaws,theteethofChondrichthyesareimbeddedinafibrousmaterialsothatwhenonebecomesbrokenorworndown,itisreplacedbyanothermovingforwardfrombehind,withnewtoothbudsdevelopingasneeded.
While some species of this class lay egg cases, most are consideredovoviviparous,withfemalesgivingbirthtoliveyoung.Malesofthesespeciestendtohavemodifiedfinscalledclaspersthatareusedtoinseminatethefemale.Pregnantfemalesoftenstopeatingandselectisolatednurseryareastogivebirth,butoftenleaveshortlythereafter.
MarineConservationScience&Policy:CartilaginousFishandDogfish
DissectionGradeLevel:
4th-12th
SubjectAreaScienceBiologyDuration1.5Hrs
BodyofKnowledgeLifeScienceNatureofSciencePhysicalScience
BigIdeaOrganizationandDevelopmentofLivingOrganisms.ThePracticeofScience
StandardsSC.3.L.15.1Classifyanimalsintomajorgroupsaccordingtotheirphysicalcharacteristicsandbehaviors.SC.5.L.17.1Compareandcontrastadaptationsdisplayedbyanimalsthatenablethemtosurviveindifferentenvironmentssuchasbehaviorsandphysicalcharacteristics.
SC912.L.14.2Relatestructuretofunctionforthebodypartsofanimals.
Benchmarks:
MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.2
BackgroundMost speciesalso featurea tapetum lucidum, a layerof tissue thatmaximizes light
reflection in the eye, allowing for superior night vision. While this adaptation is particularlyuseful to thenocturnal carnivoresof theChondrichthyes class, feedingduring theday is alsocommon.Thedietofthisclassvaries,someeatingalmostanythingfrombirdstosealstotunatoothersharks;otherslikethewhale,baskingandmegamouthsharkspreferplankton.
Whilea fewof these species venture intobrackishand freshwater,mostare foundstrictly inmarine habitats.While some species like the bonnethead shark spend their entireliveswithinahundredmilerange,othersliketheblueandmakosharksmigratethousandsofmilestobreedandhunt.Themajesticgoldencow-noserays,measuringupto6½feet,migratetwiceayearfromMexicotoFloridatoNewEnglandingroups,orfevers,ofupto10,000!
Thereareat least1,100knownspeciesof cartilaginousfish,ranging insizefromtheshort-nosedelectricrayat4 inchestothemassivewhaleshark,whichgrowsupto30ft.andcanweighup to10 tons.Colorationvaries,butmost featureadistinct lateral lineandmanyshowcountershading, adark-upperand light-lowerbody thathelps them camouflage in thewater.Whilemostsharkslivebetween20and30years,andmostraysandskatesanaverage40-50years,thespinydogfishandwhalesharkhavebeenknowntosurviveforoveracentury.Mostcartilaginousfishareconsideredapexpredators,organismsatthetopoffoodchains.Asapex predators, these organisms play a crucial role in sustaining the health of the marineecosystem,maintaining stability by keeping the prey species’ populations balanced.Withoutsharks, the increased populations of smaller fish cause a crash in plankton, upon which theentire foodwebdependsasprimaryproducers.Humans alsouse cartilaginous fish to createvariousproducts,includingmeat,sharkliveroil,leather,jewelry,rope,andevendrumheads.
Despite their importance, cartilaginous fishhavedeclined by80%,withone thirdofspeciesfacingextinction.Thesepopulationdropsaremostlyduetoanthropogenic,orhuman-causedthreats.Marinepollutionfromfisheries,plasticthatamassesinapexpredatorsthroughbioaccumulation, agricultural and urban runoff, coastal development and sewage destroyhabitat and prey populations. Overfishing threatens these species on multiple levels: bydecreasingtheirfoodsourcesaswellasunintentionallytanglingtheminnetswheretheyoftendieneedlesslyasbycatch.Byfarthegreatestthreattomostspeciesisfishing,as126,000tonsof rays and an estimated 100million sharks are killed each year, about 73million of thesedeaths due to finning. Finning refers to the practice in which a fisherman cuts off just theshark’sfin,throwingthebodyoverboardtodieaslowdeathbysuffocationorpredation.Theproblems inthefoodwebarealreadyevident inan increase in jellyfishnumbersandasteepdecline in fish populations. In order to protect these fascinating creatures, individuals canreduceplasticuse,symbolicallyadoptagreatwhite,donatetoconservationorganizations,urgegovernment officials to limit fisheries and increase marine protected areas, consume onlysustainableseafood,andeducateothersontheimportanceofallcartilaginousfish.
SupplementalResources1-“Sharks.”NationalGeographicEducation.hfp://educa,on.na,onalgeographic.org/search/?q=sharks2-“SharksandRays.”SmithsonianNaturalMuseumofNaturalHistory—OceanPortal.hfp://ocean.si.edu/ocean-life-ecosystems/sharks-rays3-VirtualTour:“Sharks:PredatorsinPeril.”OdysseyEarth.hfp://www.odysseyearth.com/videos/sharks-predators-in-peril/
Vocabulary:
CartilaginousFish:Aclassoffishcharacterizedbyarubberycartilageskeleton,complexanddiversebodies,andspeciesthatincludesharks,rays,skates,sawfishandchimaeras.Cartilage:Adenseconnectivetissuethatislighterandmoreflexiblethanbone.DermalDenticles:Thetooth-likescalesofcartilaginousfish.Ovoviviparous:Producingyoungbymeansofeggsthathatchwithinthefemalebody.
Claspers:Apairofappendagesonmalesharksandrays,usedforreproduction.
TapetumLucidum:Alayeroftissuewithintheeyethatmaximizeslightreflectiontoallowforsuperiornightvision.Gills:Pairedrespiratoryorgansofwhichextractoxygenfromwaterflowingoverthesurface.
Countershading:Aprotectivecolorationofsomefishwithdistinctdelineationbetweenadarkupperandalightlowersection.ApexPredators:Anorganismresidingatthetopofafoodchain,uponwhichnootherorganismsprey.
Bycatch:Theunwantedfishandmarineorganismscaughtincommercialfishingnets.Finning:Aprocessbywhichonlythefinisremovedfromasharkwhilethebodyislefttodie.
MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.3
DogfishDissectionMaterials
• Alargedissectiontray• Surgicalscissors• Scalpel• Probe• Forceps
Procedure
1. Dividestudentsintosmallgroupsof3-4.Explainthatasteamsofichthyologists,eachgroupwillbedissec,ngadogfishspecimeninordertobeferunderstanditsorgansandtheirfunc,ons.HandeachgrouptheirmaterialsandreadtheGuidelinestogether.Anincisiondiagramshouldbeplacedontheboardordemonstratedonanoverheadprojector.
2. Studentsmaywishtoassignonepersontonotetakingduringthedissec,on,comple,ngtheassignedsec,onsoftheworksheet.
3. Studentsshouldmeasureandexaminetheexternalfeaturesofthedogfish.4. Studentsshouldbeginthedissec,onbycarefullyfollowingtheincisiondiagram.5. Studentsshouldexaminethemusculatureofthespecimen.6. Havestudentsexaminethediges,vesystemofthespecimen.Theyshouldthen
removethoseorganstoexaminetheurogenital,nervousandcirculatorysystems.7. Studentsshouldcleanupamerthedissec,onbyplacingalldogfishpartsinthebag,
securethebagwitharubberband,andplacethebaginoneoftheusedspecimenboxes.Theyshouldwashalldissec,ontoolsandthetray,andreturntoolsandtraytotheteacher.
8. StudentsshouldallcompletetheirSharkAnatomyworksheets.Goovertheques,onsasaclassandencouragediscussionontheimportanceothescien,ficmethod,thesimilari,esanddifferencestohumananatomy,andtheevolu,on,func,onandimportanceofthebody’ssystems.
9. Dissec,onExtension:Studentsshouldresearchanddiscusstheethicsofdissectionwithaparentoradult.Studentsshouldprepareaoflistprosandconsandformulatetheirownopinion.Studentsshouldsummarizebothargumentsandelaboratetheirowndecisioninaparagraph.
AnswerKey1.D 5.E2.C 6.B3.F 7.A4.G8.Cartilaginousfishplayanimportantroleinmostmarinefoodwebsasapexpredators,helpingtomaintainbalanceinecosystems.9.Cartilaginousfisharethreatenedbyfinningandunsustainablefishingpracticesthatreducepreyspeciesandleadtobycatchofcartilaginousfish,andotheranthropogenicfactorslikebioaccumulationfromcontaminants.10.Individualscanhelpprotectthesespeciesbyeatingsustainablycaughtseafood,supportingwildlifeorganizationsandprogramslikeAdopt-a-Shark,andeducatingothers.
CartilaginousFish:Aclassoffishcharacterizedbyarubberycartilageskeleton,complexanddiversebodies,andspeciesthatincludesharks,rays,skates,sawfishandchimaeras.ApexPredators:Anorganismresidingatthetopofafoodchain,uponwhichnootherorganismsprey.Bycatch:Theunwantedfishandmarineorganismscaughtincommercialfishingnets.
Finning:Aprocessbywhichonlythefinisremovedfromasharkwhilethebodyislefttodie.
Havestudentsresearchanothercartilaginousspecieswithaparentoradult.Havethemcutconstructionpaperlengthwiseintobookmarksize.Ononeside,thestudentshouldillustratetheirchosenspecies,whiletheothersideshouldfeatureitsname,habitat,food,andthreefunfacts.
HavestudentscompletetheCartilaginousFishworksheetinclass.Intheirsciencejournal,havethemwriteaparagraphsummarizingtoday’slessonanditsrelevancetothem.
UniversityofMiami–SharkResearch&ConservationProgram
ExtensionActivity:
Assessment:
Vocabulary:
ProgramPartner:
MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.4
MSCP
SharkAnatomy
SectionII:TheDigestiveSystem5.Illustratethedigestivetractfrommouthtoanus.Labeltheorgans.
6.Howdoestheoilintheliveraidinbuoyancy?________________________
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7.Howdoestheshark’sdigestivesystemcomparewiththatofahuman?_______
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Sec,onI:ExternalAnatomy1.Illustratetheexternalanatomy.Measurethespecimenandlabelfeatures.
2.Whatinterestingthingsdoyouobserveabouttheskinandexternalorgans?_____________________________________________________________________
3.Whatpurposemightthelaterallinesystemserve,especiallyforafishinmurkywaters?______________________________________________________________
4.Istheshark’sskinasthickasyouexpectedittobe?Whyorwhynot?__________
_____________________________________________________________________
9.Unlikeamammal’sheart,theshark’sheartcirculatesdeoxygenatedblood.Whereisthebloodoxygenatedintheshark?_____
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10.Isthesharkmaleorfemale?Whatinternalandexternalfeatureshelpedyouidentifysex?__________________________
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8.Illustratetheheart.
Sec,onIII:InternalOrgans
11.Whatisthelargestpartoftheshark’sbrainandwhy?_________________
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12.Howistheshark’sskeletondifferentfromourown?__________________
________________________________________________________________
13.Whatdidyoufindinterestingaboutthisdissectionandwhy?___________
________________________________________________________________
SpinyDogfishDissec,on
MarineConserva,onScience&PolicyCurriculum–2012,2015DeeringEstate.Allrightsreserved.5
MSCP
CartilaginousFish
8.Whyarecartilaginousfishimportant?____________________________________________________
9.Whataresomeofthethreatsthatareaffectingcartilaginousfish?_____________________________
___________________________________________________________________________________
10.Whatcanyoudotohelpprotectthesefascinatingandimportantcreatures?____________________
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Thecartilaginousfishclasscontainsover1,100knownspeciesofsharks,rays,skates,sawfishandmysteriouschimaeras.Thesespeciesvaryinsize,shape,colorandbehavior,butallfeatureaskeletonmadeofcartilage,gills,nostrils,andtiny,tooth-likescalesthatprotecttheirskinandfeellikesandpaper.Cartilaginousfishplayanessentialroleintheecosystem,butmanyareendangered.
Iden,fythespeciesintheabovephotos:
1. ______Thelarge-toothedsawfishcanuseitslongsnouttodigthroughsedimentorcutpreyinhalf.2. ______Themajes,cmantaraycanhaveawingspanof15m.andliveuptoahundredyears.3. ______ThelifleskatelivesintheAtlan,candisomenusedformedicalresearch.4. ______Despitebeingtheworld’slargestfish,thewhaleshark’sdietconsistsoftheocean’ssmallestorganisms,
filteringplanktonthroughitsmouth.5. ______ThespofedchimaerahuntssmallfishandcrustaceansoffthePacificcoastofNorthAmerica.6. ______Becauseitseyesareonbothsidesofitsunusualhead,thehammerheadisabletoscanmoreoftheoceanfor
itsfavoritefood:s,ngrays.7. ______Thegoldencow-noseraymigratesannuallyfromMexicotoFloridaingroupsofover10,000.
A B C
D E F
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