Exploring Biodiversity - 1

BIL161:IntroductiontoExploringBiodiversityTerrestrialEcosystems

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,

fromindividualorganismtobiosphere.

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)ofspeciesrichness is thenumberofspecies inasampledividedby 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 team will be collecting samples from two different, naturally occurring habitats (of yourteam’schoice)tomeasureandcomparetheirrelativebiodiversities.

Forexample,yourteammaydecideto§ comparespeciesrichnessbetweentwosystems§ compareabundanceofparticularspeciesbetweentwosystems§ compareabundanceoflargertaxonomicgroupsbetweentwosystems§ insertyourcleverandrelevantideahere

Youmightwishtoconsiderwhetherbiodiversitydiffersbetween§ openvs.closedsystems§ smallvs.largesystems§ differenttimesofdayinthesamesystem

§ differentlevelsoffertilizerorpesticide§ differentlevelsofotherpollutants§ insertyourcleverideahere,too.

Yourtaskwillbetoidentifytwonaturallyoccurringhabitatsthatyoupredictwillhavedifferencesin someaspectofbiodiversity foraspecific, logicalreason. Youmustbe able tophysically takesamplesintheselocalitieswithtechniquesdescribedinthelabmanual(andlinkedvideos).

Therearemanyenvironmentsfromwhichyourteamcanchoose.

§ Manicuredlawnvs.fieldlefttogo“feral”§ Gardendominatedbyexoticspeciesvs.gardendominatedbynativespecies.§ Twodifferentnaturalecosystems§ Similarecosystemsintwodifferentlocalities§ Oncemore,insertyourclever,relevantideahere

Your team will have the option of performing a census on either plant species orinvertebratespecies.Youmaynotincludeanyvertebratespeciesinyoursampling.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 importantpointsshouldbetodescribe furtherresearch thatwouldhelpyouto identifyspecificfactorsaffectingtheaspectsofbiodiversityyouhaveexamined.

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IV.EnvironmentalFactorsandBiodiversityIn thissectionyouwill learn to identifyenvironmental some factors toconsiderwhenchoosingtwohabitatstosampleandcompare.

Remember that you will not be able to positively identify the factors responsible for anydifferencesinbiodiversityyouobservewithoutadditional,controlledexperiments.Butthis,alongwithyour literature search, shouldhelpyoudevisea logical, informedoverall hypothesis thatcanbetranslatedintotestablenullandalternativeexperimentalhypotheses.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.

Notethatevenregulatorshavetolerancelimitsforvariousenvironmentalfactors.

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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.Biodiversitywilldifferamongnaturalhabitatswithdifferentsoiltypesandcomposition.

But consider the implicationsof climate change. SouthernFlorida ispredicted tobeoneof thegeographicregionshardesthitbyevensmalldegreesofsealevelrise.Thiswillmeanmorethanjustfloodingathightide.Saltwaterintrusionunderneathterrestrialhabitatsisalreadybecomingaprobleminsomecoastalareas,affectingtheabilityofplantstoobtainsufficientfreshwater.Themost abundantdissolved ions in aquatichabitats are sodium, chloride,magnesium, sulfate, andcalcium. Plants need some of these as nutrients. But too high a concentration in the soil canpreventplantsfromobtainingthewatertheyalsoneed.

§ Marinewatercontains30-50gramsofsaltsperliter.o Modernseawaterishyperosmoticwithrespecttoatypicalcell’scytosol.

§ Freshwaterisdefinedashavinglessthan0.5gramsdissolvedsaltsperliter.o Freshwaterishypoosmoticwithrespecttoatypicalcell’scytosol.

§ Brackishwaterisdefinedashavingbetween0.5–30gramsofdissolvedsaltsperliter.o Thiswiderangemeansthattheterm“brackish”isratherimprecise.o Tidalflowcancausewidefluctuationsinsalinityoverthecourseofaday.o Brackishionfluctuationscanpresentosmoticchallengestomanyorganisms.

C.OtherNaturalAbioticFactorsTerrestrial habitats throughout southern Florida can vary in light level, temperature, soilnutrientandchemicalcomposition,andanynumberofother factors. Thesefactorscanvarynotonlyamongecosystems,butwithinasystemoverthecourseofaday,month,oryear.Onedifficultyfacedbyeveryecologistiscontrollingformultiplevariables.Whenyouselectthetwosystemsyouwishtocompare,youandyourteamshouldlistallpossibledifferencesbetweenthetwohabitatsthatcouldaffectbiodiversity.Yourteamshouldbeabletoproposeadditionalstudiesthatwouldallowyouto

§ determinewhetheraparticularfactoraffectsbiodiversity§ explainthephysiologicalandcellularmechanism(s)responsible

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

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