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Final

Bio Final Exam Material.docx

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Department
Biology
Course
BIO1130
Professor
All Professors
Semester
Winter

Description
BioFinalExamMaterialEndofCambrianandOrdovicianThereisaperiodonplanetearththatscientistsknowaboutwheretherewasacondition600millionyearsagocalledsnowballearthThewholeplanetfrozeduringthistimeWewilltalkaboutthisperiodWhatwewillalsoseeisthatburrowingdevelopedforthefirsttimeintheCambrianeraThatwillallowfordiversitytooccurWewillalsoseeanimalsthatstarttoliveinsuitsofarmourtoallowprotectionforthemselvesagainstpredatorsAndthenfinallyinthelast1520yearstherehasbeenadevelopmentalandmolecularexplanationforwhathappenedinthistimeSnowballearthisaconceptthatsaystheplanetwascompletelycoverediniceandwasfrozensolidandthishappened3timesforaround1millionyearseachTheyarefreezethawcyclesWhydidthisoccurAndwhataretheimplicationsWhatyouhavetorealizeisthatinthelateProterozoiceverythingishappeningintheoceansandtherearenosignificantcontinentallandmassesthathaveemergedoutoftheoceansatthistimeInthelateProterozoic100millionyearsbeforetheCambrianthefirstpieceoflandemergesoutoftheoceansItactuallysitsandstraddlestheequatorItsitsrightonetheequatorandaveryunusualthinghappensForthefirsttimerainsandwaterthatarefallingfromtheskywateriserodingrockAsthewatermovesoverititslowlydissolvestherockFromthiscalciumcomesoffoftherocksWhatyoualsohavetorealizeisthattheoceanandthecarbondioxideintheatmospherearounditareinequilibriumwitheachothernormallyItisexpressedintheequationCO2HOHCOwhichcanseparateintoitsionicformsofHandCO2Thisisthe2233carbonatebicarbonatecycleintheoceansCarbondioxidewillalwaysdissolvetoacertainextentinthewatersandacertainamountofitformsabicarbonateatomForthefirsttimewehavecalciuminhereinlargelevelsbecauseitisfromtheerosionofacontinentovertimeAndwhathappensisthatthecalciumwillbindwiththebicarbonatetomakecalciumbicarbonatewhichisinsolubleinwaterandwillsettledownThisisthesedimentationthatoccursnaturallyinanoceanTheyturnintothingslikelimestoneandfinesedimentsetcItisnormalandnaturalButwhatyouhavetorealizeisthatthecalciumhadneverbeeninherebeforeSoifwestarttomovethecarbonoutofsolutionandinsedimentswiththepresenceofthenewcalciumwearegoingtobreaktheequilibriumoftheoceansandtheairAsthecalciumpullsthecarbonoutasbicarbonatewearegoingtodissolvemorecarbondioxideintothewaterAndasthatcarbondioxidegetsdissolveitisgoingtoreactwiththecalciumandcomeoutofsolutionassedimentsAndthishappensonsuchalargescalethattheamountofcarbondioxideintheatmosphereisgoingtostarttodiminishAnditgetsworsebecauseifthereisanysilicainthereanothermajorelementofrocksthatprecipitatesthecarbonasbicarbonateoutofthewaterevenfasterSothemineralscomingfromtheerosionaretakingthecarbondioxidethatsintheformofbicarbonatetakingitoutofthesystemandturningitintosedimentsandtheoceantomaintainitsequilibriumaresuckingitoutoftheairmakingthelevelsdecreaseWhyareweconcernedaboutthis1ItisagreenhousegassoittrapsheatfromthesunItformedablanketaroundtheearththatkepttheheatinIfweremovetheblankettheheatradiatesawayandearthcoolsItwasalsothoughtthattherewasalotofmethaneinthisearlyatmosphereandsoallofthatworkbythecyanobacteriathatwerecreatinglargeamountsofoxygenthatoxygenreactswithmethaneanddestroysitMethaneisalsoareallygoogreenhousegasSoweseealossoftheisolativepropertiesaroundtheplanetofthegreenhousegassesandtheplanetcoolsAsitcoolstheicecapsstarttoforminthenorthernregionsandofcourseTheicecapsarewhitewhichreflectsunlightwhichdecreasestheamountofabsorbableenergytheearthcanabsorbSonotonlyarewedecreasingtheinsolationofthegreenhousegasesbuttheiceisalsobecomingreflectiveandlessoftheearthssurfaceisbecomingavailabletoabsorbradiantheatWhattheybelievehappenedwasthatwiththese2thingsworkingtogetheritactuallygottothepointwhereicemassesweresobigthatnotenoughradiantheatwasbeingabsorbedbytheearthtomelttheaccumulationiceAtthispointitwasatippingpointTherewasnostoppingitAsaresultthewholeplanetfrozeoverandbecamesnowballearthThereweretremendousimplicationsforthelifeintheoceansofthistimeTherewouldbenolightpenetrationsoprimaryproductivitywoulddropYettheoceanwasrichIthadlotsofpotentialbutsnowballearthstoppeditdeadinitstracksUltimatelywhathappensisthereisstillvolcanicactivityintheoceansandsocarbondioxideisstillbeingproducedIteventuallybecomesabletopenetratethroughtheicemassontheearthSothecarbondioxidelevelswillriseagainandastheyrisethegreenhouseaffectcomesbackandtheplanetwarmsagainAndattheinterphasewhentheplanetisthawingoficeandterrestrialenvironmentitchangesveryquicklybecausethereisalotofradialenergyavailablethatgetstrappedmeltstheiceandtheicestartstoretreatSobasicallyitisbelievedthatovera10millionyearperiodtheearthfrozeandthenthawed3timesWhentheicefinallyretractedforgooditleftanoceanthatwasstrippedofmanyofthethingsthatwereoriginallythereIncludingaswewillseesomeearlyattemptsofmulticellularlifeSowhydidittakesolongformulticellularlifetooccurWellthestagewasprobablysetforthembutlikeclimaticmessontheplanetstoppeditIwontprogressuntilaftersnowballearthisdoneWhatisparticularlyinterestingisthatifwelookattheperiodoftimeonearthwhenitwasfrozensolidthecryogenianandthenlookatwhathashappenedinthelast20yearswehavefound2typesoffossilizedthathavereallymadeusstarttoquestionwhethermulticellularlifestartedbeforetheCambrianornotDoushantuoOneofthethingsthathavemadeforthisisthediscoveryofthefossilsTheyareabout600millionyearsold050millionyearsbeforetheCambrianWhatyounoticeaboutthemisthattheylooklikesmallcellsthathaveundergonecelldivisionsWhatthethinkingisisthatthesearefossilizedembryosfrom500millionyearsbeforetheCambrianWhattheimplicationsofthatarethatifthisistruethenthatmeansthey2aremulticellularBecauseevenembryoshavecelltocellcommunicationSothisimpliesthatmulticellularityarrivedbeforetheCambrianThenabout20yearsagoafossilbedcalledtheediacaranfossilsthatarerichinthesetypesoffossilswasfoundalsopredatingtheCambrianbyhundredsofmillionsofyearsTheseonesarefoundinMistakenPointNewfoundlandinagreatslabofanancientrockthathasbeenexposedWhenyouwalkacrossityouseefossilsoforganisedanimalsTheyalsosaythatlifeoccurredpriortotheCambrianexplosionTheseediacaranfossilsweresuchahugediscoveryandweresoimportantthattheyaddedanewgeologicalperiodintothehistoryofearthinwhichtheyexistedSowhatthisgivesusaveryunusualquestionwhendidmulticellularlifearriveWasitduringtheCambrianexplosionOrbeforethiswiththeseveryoddorganismsthatwefindinNewfoundlandthathaveplansoflifeofaggregatesofcellswithbranchingpatternedbodiesSomaybeitdidnthappenatalloncebutthereisdefinitelysomethingthathappensintheCambrianwegetourfirstburrowinganimalsThefossilstellusthatlifeifitwashappeningwashappeningonthesurfaceoftheoceansthatwascoveredinanalgalmatthatwasimpenetrableThatalgalmatwouldpreventanythingfromdiggingitswaythroughitAndsoyougetEdiacaranfossilsthatwerelyingonthematandweredoingsomethingtogetfoodwhichwehavenoideahowThenyoustarttogettheanimalsandorganismsthatmoveacrossthatmatUnderneathittrappedunderthematisabunchoforganismdebrisandmaterialsbecauseasitgrowsitbuildsontopofmaterialthatisalreadythereThefirstanimalsthatcanbreaktheirwaythroughthatcantapintoanewfoodreservethatnooneelsehasThatisexactlywhatthewormlikeanimalsdidTheywereabletoburrowthroughthematandtaptheorganicsthatweredownthereSoyougetanexplosionoftypesThemolluscsarealsoimportantinthisbecausetheycanusetheirradulastopenetratethroughthealgalmatanddestroyitandastheymoveacrossittheystartmakingthefoodunderitavailabletoallotherorganismsTheyburrowersareimportantbecausenotonlydidtheystarteatingthefooddowntheretheyalsocouldhideintheirburrowsforprotectionThewormscouldreachoutsideoftheirburrowsfeedandthenanchorthemselvesinplaceandbeabletocomeinandoutSonotonlytodowehaveauniquefoodsourcebutwealsohaveanenvironmenttoprotectthesoftbodiedorganismsUpuntilnoweverythingwasmovingaroundonthesurfaceNotonlywerethereburrowersthereweretheorganismsthatbuiltarmourSimilartothemolluscswhobuildshellwithcalciumtherewerearthropodswhousethecalciumintheirouterexoskeletonandstrengthenthemselvesSOwehaveabunchofanimalslivinginprotectivesuitsIfyoucanprotectyourselfyoucangrowbiggerusingthearmourtoprotectyourselfandthenthingsthatdiversifyThediversitychangedfromsmalllittleanimalsfeedingonalgaetobiggerinvertebratesthatatethesmallonesetcDiversityexplodesOneoftheotherbigquestionsinbiologyiswhenyougetthesemassexplosionsofpatternedorganismsishowisthatcodedforinthedevelopingembryoHowdowe3
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