bil 161: introduction to exploring biodiversityexploring biodiversity - 1 bil 161: introduction to...

Exploring Biodiversity - 1

BIL161:IntroductiontoExploringBiodiversity

Biodiversity is defined as the degree of variation of living organisms within a particularecosystem (or the entire planet). Your first research project is designed to introduce you to anaturalist’sperspectiveofbiodiversity.

I.BiodiversityBiodiversitycanbeconsideredatvarious,hierarchicallevels(Figure1).Inbiologicalterms…• A species is a group of organisms ableto interbreed in nature to producefertile,viableoffspring.

• A population is defined as all theindividualsofthesamespecieslivinginadefinedregion.

• A community is defined as all thepopulationslivinginadefinedregion.

• An ecosystem comprises the biotic(living) and abiotic (non-living)componentsofadefinedregion.

• A landscape comprises the patterns ofand interactions between ecosystemswithinaregionofinterest.

• The biosphere comprises the regionsonearthwherelifecanexist.

Figure1.Theecologicalhierarchy,from

individualorganismtobiosphere.

Thebiodiversityofaspecificecosystemisdeterminedby itsabiotic factors. Everyspecies(andpopulation)evolvesspecificrequirementsandtolerancelimitsforsuchfactorsas

• temperature• light• humidity

• variousnutrients• variousharmfulchemicals• pH

• etc.

Theevolutionofpopulationswithinanecosystemalsocanbeaffectedby• theirownpopulation’sdensity• interactionswithotherpopulations

Withinanecosystem,microhabitatscharacterizedbyspecificphysicalfactorsprovideresourcesforspeciesevolvedtolivewithinthem.Forexample,pondecosystemmicrohabitatscouldinclude

• emptygaps(interstices)betweenthelivingmatterofplants• areasunderrocksandstones• theopenwatercolumn• sedimentatvariousdepths• thewatersurface

Speciescompositionanddiversityvarieswithecosystemandmicrohabitatconditions.Abioticcomponentsdeterminethecompositionandabundanceofbioticcomponents.Bioticcomponents,inturn,affecteachother'sabundanceanddiversity.

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II.MeasuresofBiodiversityEcologistsusevariousindicestodeterminebiodiversitywithinandamongecosystems.Youwillusetwocommonlyemployedmeasures,speciesrichnessandspeciesabundance.A.SpeciesRichnessThe simplest measure of an ecosystem’s biodiversity is species richness (S), the number ofdifferentspeciesfoundinacollectedsample.

Speciesrichnessdoesnottakeintoaccounttheabundanceofeachspecies,onlytheirpresence.

Menhinick’s Index(D)of species richness is thenumberof species ina sampledividedby thesquarerootofthenumberofindividualsinthesample.

Inwhich:

s=thenumberofdifferentspeciesinasampleN=thetotalnumberofindividualorganisms(allspecies)inthesample

B.SpeciesAbundanceTheabundanceofaparticularspeciesinanecosystem(ormicrohabitat)issimplythenumberofindividualsinthatecosystem(ormicrohabitat).

Therelativeabundanceofaparticularspeciesinanecosystemisameasureofhowcommonorrarethatspeciesisincomparisontootherspeciesinthesameecosystemormicrohabitat.

Therelativeabundanceofanygivenspeciesisthenumberofindividualsofthatspeciesdividedbythetotalnumberofindividualsofallspeciescombined.

Forexample,ifyoucollectedaonemilliliter(mL)sampleofpondwaterandfoundthefollowingnumbersofeachofthreespecies:

100diatoms(Neidiumpseudodensestriatum) 50nematodes(Psilenchushilarulus) 5mosquitolarvae(Aedesaegypti) 155TOTALINDIVIDUALS

Thentherelativeabundanceofeachspecieswouldbe:

Neidiumpseudodensestriatum: 100/155=0.64 Psilenchushilarulus): 50/155=0.32 Aedesaegypti 5/155=0.03

Youmay encounter othermeasures of biodiversity in the literature search youwill perform toprepare for this project. You may use them, if your team decides it is appropriate to do so.However,themeasuresaboveshouldserveyouwellforthisproject.

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III.TheNatureoftheResearchProjectYourteamwillNOTbemanipulatinganexperimentalsystem.Therewillbeno“treatment”or“control”groups.

Theresearchprojectyouareabouttoundertakeisbestclassifiedasasurvey.Your teamwillbe collecting samples from twodifferent,naturallyoccurringaquatic systems tomeasureandcomparetheirrelativebiodiversities.

Forexample,yourteammaydecideto• comparespeciesrichnessbetweentwosystems• compareabundanceofparticularspeciesbetweentwosystems• compareabundanceoflargertaxonomicgroupsbetweentwosystems• insertyourcleverandrelevantideahere

Youmightwishtoconsiderwhetherbiodiversitydiffersbetween• openvs.closedsystems• freshwater/brackish/marinesystems• smallvs.largesystems• differenttimesofdayinthesamesystem

• differenttidallevelsinthesamesystem• habitatswithdifferentlevelsoffertilizerrunoff• habitatswithdifferentlevelsofotherpollutants• insertyourcleverideahere,too.

Yourtaskwillbetoidentifytwolocal,naturallyoccurringaquatichabitats/microhabitatsthatyoupredictwillhavedifferencesinsomeaspectofbiodiversityforaspecific,logicalreason.

Therearemanylocalaquaticenvironmentsfromwhichyourteamcanchoose.

• ClosetothecenterofcampusliesbrackishLakeOsceola.Itisconnectedtotheoceanbyalong network of canals, so species fromboth freshwater andmarine environments haveaccesstothelake.

• The freshwater lake on the campus of Florida International University is anotherpossibleresource.

• Coral Gables and nearby communities are dotted with many man-made ponds andcanals.

• WithindrivingdistanceofcampusareaccessiblemarineenvironmentssuchasMathesonHammock,CrandonPark,andotherpubliccoastalareas.

Yourresearchquestionislimitedonlybyyourimagination.Considerinteresting,relevantpossibilities,andusetheseaskeywordsinyourliteraturesearch.IMPORTANT:Yoursurveyprojectisapilotstudy.

Apilotstudyisasmallscale,preliminarystudyconductedtoevaluateasystempriortofull-scaleresearch. Eachof the systems listedabovehasmultipleenvironmental factors that couldaffectbiodiversity.Youmaylistdifferencesbetweenyoursystemsandpredicttheirpossibleeffects.However, you will not be able to make a definitive statement about the reason for anyobserved difference in biodiversity between your systemswithout additional, controlledresearch.Whenyourteamprepares its finalpresentation,oneofyourmost importantpointsshouldbetodescribefurtherresearch thatwouldhelpyoutoidentifyspecificfactorsaffectingtheaspectsofbiodiversityyouhaveexamined.

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IV.AquaticEnvironmentalFactorsandBiodiversityIn thissectionyouwill learn to identifyenvironmental some factors toconsiderwhenchoosingtwohabitatstosampleandcompare.

Remember that you will not be able to positively identify the factors responsible for anydifferences in biodiversity you observe without additional, controlled experiments. But this—alongwithyourliteraturesearch—shouldhelpyoudevisealogical,informedoverallhypothesisthatcanbetranslatedintotestablenullandalternativeexperimentalhypotheses.A.Homeostasis:RegulatorsandConformersHomeostasisisthemaintenanceofconstantinternal(controlled)variablessuchas

o temperatureo pHo watercontento ionconcentrationso etc.

Speciesdifferintheirabilitytokeepcontrolledvariablesdistinctfromexternalenvironmentalconditions.Becauseanorganism’sreproductivesuccess(thekeystoneofnaturalselection)isaffectedbyitsabilitytomeetenvironmentalchallenges,aspecies'abilitytosurviveenvironmentalextremesreflectsitsevolutionaryhistory.

• Aregulatormetabolicallymaintainshomeostasisinresponsetoenvironmentalchanges.o Aregulatorcancontrolthevalueofaparticularcontrolledvariable.

• Aconformerislessabletometabolicallymaintainhomeostasisinresponsetoenvironmentalchanges.

o Thevalueofaconformingcontrolledvariableisgovernedprimarilybytheexternalenvironment.

Aspeciesmaybearegulatorwithrespecttosomecontrolledvariables,andaconformerwithrespecttoothers.(Figure2)

Figure2.Asalmon’sbodytemperaturevarieswithenvironmentaltemperature.It’schlorideconcentration,however,iscontrolledmetabolically,anddoesnotvarywithenvironmentalchlorideconcentration.Thus,thesalmonisathermoconformerandanosmoregulator.

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Notethatevenregulatorshavetolerancelimitsforvariousenvironmentalfactors.A mammal like you can metabolically control internal body temperature. But unprotectedexposuretoextremetemperaturescanoverridehomeostasis,withpossiblydireconsequences.

Whenyoudesignyourexperimentandanalyzeyourresults,considerwhether theorganisms inyour systems are conformers or regulators with respect to various environmental factors, andwhatthetolerancelimitsforthoseenvironmentalfactorsareforeachspecies.B.BioticandAbioticEnvironmentalFactorsDifferentspecieshavedifferenttolerancestodissolvedsalts.Biodiveristywilldifferamongnaturalfreshwater,brackish,andmarineenvironments.

But consider the implicationsof climate change. SouthernFlorida ispredicted tobeoneof thegeographicregionshardesthitbyevensmalldegreesofsealevelrise.Thiswillmeanmorethanjustfloodingathightide.Evenwhentidesarelow,saltwaterintrusionintofreshwateraquifersmay have a profound effect on species diversity. The most abundant dissolved ions in mostaquatichabitatsaresodium,chloride,magnesium,sulfate,andcalcium.

• Marinewatercontains30-50gramsofsaltsperliter.Modernseawaterishyperosmoticwithrespecttoatypicalcell’scytosol.Most(notall)marineprotists,plants,andinvertebratesareosmoconformers.However,somemarineorganisms(e.g.,bonyfish)expendmetabolicenergytoretainwaterinthecytosolandremoveions.

• Freshwaterisdefinedashavinglessthan0.5gramsdissolvedsaltsperliter.Freshwaterishypoosmoticwithrespecttoatypicalcell’scytosol.

• Brackishwaterisdefinedashavingbetween0.5–30gramsofdissolvedsaltsperliter.Thiswiderangemeansthattheterm“brackish”isratherimprecise.Tidalflowcancausewidefluctuationsinsalinityoverthecourseofaday.Brackishionfluctuationscanpresentosmoticchallengestomanytypesoforganisms.

C.OtherNaturalAbioticFactorsAquatic habitats throughout southern Florida can vary in light level, temperature, chemicalcomposition, and any number of other factors. These factors can vary not only amongecosystems,butwithinasystemoverthecourseofaday,month,oryear.Onedifficultyfacedbyeveryecologistiscontrollingformultiplevariables.Whenyouselectthetwosystemsyouwishtocompare,youandyourteamshouldlistallpossibledifferencesbetweenthetwohabitatsthatcouldaffectbiodiversity.Yourteamshouldbeabletoproposeadditionalstudiesthatwouldallowyouto

• determinewhetheraparticularfactoraffectsbiodiversity• explainthephysiologicalandcellularmechanism(s)responsible

D.AnthropogenicFactorsAnthropogenic (from the Greek anthropos (human) and genesis (origin)) factors are thosegeneratedbyhumans.Suburbanareasaresubjectedtohumandisturbancesuchaspesticideandfertilizerrunoff,physicaldisruption,sanitation/clearingefforts,etc.Howmightthesefactorsaffectspeciesdiversityandspeciescompositionofanearbyaquaticsystem?

Consider various factors that might affect biodiversity, and use these as keywords in yourliteraturesearchtofindbackgroundinformation.