2021
AP
®
Environmental
Science
Scoring Guidelines
Set 2
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AP® EnvironmentalScience2021 Scoring Guidelines
Question1:DesignanInvestigation 10points
(a) (i) Identifythescientificquestionthatresultedinthedatapresented inthegraph.
Acceptoneofthe following:
Whatisthe relationshipbetweenslopeandannualerosionrateforfourdifferentland
usetype
s?
Doescroprotation/tilling/nottilling/usingcovercropsonvariousslopes
increase/dec
rease/changeerosionrates?
1point
(ii) Identifytheagriculturalpracticethatcouldbeusedona15%slopewithoutleadingtoa
higher thantolerablelossofsoil.
Croprotation
1point
(iii) Describetheeffectofaddingacovercropcompared tousing the no‐tillmethod.
Acceptoneofthe following:
Addingacovercropreducesthe annualrateofsoilerosioncomparedtousingtheno‐
tillmethod.
Addingacovercropallowsplantingongreaterslopedlandbeforereachingtolerable
lossascomparedfortheno‐tillmethod.
1point
(iv) Identifyonenaturalmechanismofsoilerosion.
Acceptoneofthe following:
Moving/flowingwater
Rainfall
Wind
1point
Totalforpart(a) 4points
(b) (i) Identifythedependentvariablestatedinthehypothesis.
Acceptoneofthe following:
Theamountofsedimentdischarge
Theamountofsedimentrun‐off
1point
(ii) Describeonewaytoadda
controltoimprovethedesignofthestudy.
Acceptoneofthe following:
Addaplotthatisbare/doesnothavestrawbalesorgrass(nogroundcover).
Measuresedimentdischarge/runoffpriortoplacingstrawbalesorplantinggrass
comparedtodischarge
afterthebales/grassareinplace(pre‐/post‐tests).
©2021CollegeBoard
1point
AP® EnvironmentalScience2021 Scoring Guidelines
(iii) Identifyonevariablethat wasnotdiscussedthatcouldaffect theresultsofthestudy.
Acceptoneofthe following:
• Slopeoftheplots
• Amountofrainfall
• Compositionoftheroads
• Distanceoftheplots fromroad/stream
• Sizeofthe plots
• Typeofsoila
t
theplots
•
Whenthedataarecollectedattheplots(howquicklyafterrainfall)
1point
(iv) Basedonthed
atainthetableabove,makea claimaboutthestatedhypothesis.
Acceptoneofthe following:
• Thestatedhypothesisisrejectedasmoresedimentresulted fromstrawbaleplots
(plotA)than
grassplanted
plots(plotB).
• Thedatainthetableshowsthatthegrassismoreeffective atreducingsediment
runoff.Theh
ypothesisshouldberejected.
1point
Totalforpart (b) 4points
(c) (i) Describethetypeofsurvivorshipcurve expectedforthesefish species.
Acceptoneofthe following:
Lowsurvivalrateinearlylife,followedbyincreasedchancesofsurvivalasthe
organismmat
ures.
Mostoffspringdie ataveryyoungageandfew reachmaturity.
1point
(ii) Explainwhytheinputofsedimenttoastreamcannegativelyaffectreproductionoffish
thatlayth
eireggsin thegravelofthestreambed.
Acceptoneofthe following:
Sedimentcancover/buryeggs,whichreducestheamountofoxygen,causingthemto
die.
Sedimenttakesawayusablehabitat/spaceresultinginfewer areasforthemtol
ay
eggsca
usingfewereggsto survive.
Sedimentscancarrytoxic/poisonouschemicals,whichcan negativelyimpacttheeggs
anddecrease
eggsurvival.
Anincreaseinsediment canincreasethewatertemperatureandresultinless
dissolvedoxygen/toowar
mwater,whi
chcandecreasetheviabilityoftheeggs
that
havealreadybeenlaid.
Sedimentcanincrease waterturbidity,whichdecreasesfishnavigation/abilityto
forage/efficien
cyofoxygenusewhichdecreasestheamountofeggslaid.
1point
Totalforpart(c) 2points
Totalforquestion1 10points
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AP® EnvironmentalScience2021 Scoring Guidelines
Question2:AnalyzeanEnvironmentalProblemandProposeaSolution
10points
(a) (i) Identifythelatitudinalrangewiththegreatestamphibianspeciesrichness.
Acceptoneofthe following:
BetweentheTropicofCancerandtheTropicofCapricorn
Therangebetween30degreesNan
d30degreesSlatitude
Therangebetween10degreesNand15degreesSlatitude
1point
(ii) Identifywhatbiome
this rangemostlikelyrepresents.
TropicalRainforest
1point
(iii) Describeonereasonamphibianspeciesrichnesswouldtendtobehighestinthisregion.
Acceptoneofthe following:
Morerainfall/warmtemperaturesyear‐roundare thepreferredconditionsfor
amphibians.
Greater biodiversity/highe
rNPPprovidesmorehabitat/foodsources/niches.
1point
Totalforpart(a) 3
points
(b) Thereare manyenvironmentalthreatsfacingamphibianstoday,such asdeforestation.
Describeone
possibleanthropogenicreasonfordeforestation.
Human demandforagriculture/housing/firewood/forestproducts
(medicine/food/lumber).
1point
(c) (i) Explainhowthespeciesrichnessofanecosysteminfluencesitsresponseto
environmentalstressors.
Anecosystemwithgreaterspeciesrichness/diversityismoreresilient/resistantto
environmentstressorsbecausesomespecieswill
sur
vivehelpingtorestore/stabilize
theecosystem.
©2021CollegeBoard
1point
AP® EnvironmentalScience2021 Scoring Guidelines
(ii) Explainwhyamphibianbiodiversityisdecliningglobally,otherthanfromdeforestation.
Acceptoneofthe following:
Increasingwaterpollutionincluding:
o Pollutionfrompharmaceuticalsthatcausereproductiveharm/decrease
reproductivesuccess.
o Pesticide
pollutionthatisabsorbedviatheskinan
distoxictoamphibians
leadingtodeath.
o Endocrinedisruptors(such asatrazine)canalterreproductive development
leading
todecreasednumberofsuccessfuloffspring.
Pesticide usereducesfoodsourcesforamphibians(insects),leadingtodecreasi
ng
populationsize.
Microclimaticchangesfromoverallglobalclimatechange(e.g.,warmer,drier
conditions inpreviouslycool,moistareas,lossofwetlands)
decreasesavailable
habitatleadi
ngtoadeclineinpopulationsize.
Illegalamphibiantraffickingremovesspeciesfromanarealeadingtoadecline in
populationsizes.
Introduction ofinvasivespeciesthatcompetefornichespaceleadingtoadeclinein
populationsizes.
Habitatfragmentationfromhumanactivitywouldlimitrange/reducethe abilityto
accessresources,decreasingsurvival.
Fungalinfe
ctions(suchasChytrid)causetheirskin todryout,andtheycannot
breathe.
1point
T
otalforpart(c) 2poin
ts
(d) (i) Identifyonespecificpiece oflegislationthathasbeendesigned toprotectspecies
threatenedbyextinction.
Acce
ptoneofthe following:
• EndangeredS
peciesAct(ESA)
• Conventiono
ntheInternationalTrade ofEndangeredSpecies(CITES)
• LaceyAct
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1point
AP® EnvironmentalScience2021 Scoring Guidelines
(ii) Explainhowtherequirementsofthelegislationidentifiedinpart(d)(i)specificallyprotect
speciesthreatenedby extinction.
Accept oneofthefollowing:
Legislation identified in
(d)(i)
Explanationofrequirements thatspecificallyprotectspecies
threatenedbyextinction
EndangeredSpecies
Act(ESA)
Listsendangered/threatenedplantandanimalspeciesand
preventsthemfrombeingkilledorharmed.
Designates/protectscriticalhabita
ttopromotesurvival
andrecoveryoflistedspecies.
Createsplans torestorepopulationstohealthy sizes.
Identifiesspeciesthatare threatenedbeforetheybecome
endangere
dtoprovideprotections.
Conventiononthe
InternationalTrade
ofEndangered
Species(CITES)
Aglobalagreementthatprotectsendangered/threatened
plantsandanimals(includinggoodssuchasivory,shark
fins,orrhinoceros’horns)bybanning/regulatingthe trade
ofthesespecies.
LaceyAct Prohibitsthetradeofwildlife,fish,andplantsthathave
beenillegallytaken,possessed,transported,orsold.
1point
Totalforpart (d) 2points
(e) (i) Proposeaviablesolutionthatwill
resultintheprotectionoftheendemicfrogspecies
whilestillallowingformaximumprofitofthe propertydevelopment.
Acceptoneofthe following:
Move/transplantthefrogpopulationsto anadjacentundeveloped
areapriorto
developme
n
t.
Aportionofthewetlandcanbe designatedasapark/preserve.
Wildlifecorridors(land/bri
dges)canbebuilt/
createdonaportionofthewetlan
ds.
Restrictdevel
opmentwithinam
inimumsetbackawayfromthewetland.
Projectdeveloperscangroupbuildingstogether/can buildup,n
otout.
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1point
AP® EnvironmentalScience2021 Scoring Guidelines
(ii) Justifythesolutionproposedin (e)(i)by describingapotentialadvantageoftheplan,
otherthanfrogprotection.
Acceptoneofthe following:
Solutionproposedin
(e)(i)
Justificationofhows
olutionsofferpotentialadvantages, other
thanfrogprotection
Move/transplant
frogs
Developerswillonlyhaveaone‐timedisruptionduringthe
removalbutwillnothavetodealwithcontinueddisruptions
(such asincreasinghumanpopulation,increasing use of
fertilizer/pesticides).
Developerwi
llhavethem
aximumamountof land
available.
Designateasa
park/preserve
Byprotectingareas,animalspecieswillhavemorefoodand
spaceavailabilityincreasingsurvivalrates.
Potentialeducational/environmental dr
awoflivingneara
park/preservemayallowthedevelopertochargehigher
rentsfortheapartments.
Thereisaestheticvalueofthe wetlandandits speciesforthe
peoplethatlivether
e.
Thepreservedwetlandareawillhelppreventfloodi
ng.
Useofwildlife
corridors
Byestablishingcorridors,theotherspecieswillalsonotbe as
greatlyaffect
edby multiplehabitatfragments.
Theanimalspeciescancontinuetomovebackandf
orthfor
food,shelter,andre
productionbywayofthehabitat
corridors.
Setback Byestablishingsetbacks,abufferzonewillbecrea
ted
betweenthe developmentandthewetlandarea,filtering
runoffintothewetland.
Abuffer zonewilladdprivacyforresidentsbetweenthetwo
developmen
ts.
Project
developmen
t
Bydevelopingtheapartmentsin groups/clustersandleaving
preservedwetlands,thespecieswillnot beasaffectedby
multiplehabitatfragments.
1point
Totalforpart(e) 2points
Totalforquestion2 10points
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AP® EnvironmentalScience2021 Scoring Guidelines
Question3:AnalyzeanEnvironmentalProblemandProposeaSolution
DoingCalculations 10points
(a) Describewhycoalisconsideredanonrenewableenergysource.
Acceptoneofthe following:
• Nonrenewableenergysourceslikecoalexistin afixed/finite/limitedamount.
• Theformationrateofcoalislessthantheconsumption/combustionrateofcoal.
1point
(b) Describeonepotentialenvironmentaladvantageofreplacingacoal‐firedpowerplantwith
anatural‐gaspowerplant.
Acceptoneofthe following:
• Naturalgascombustionemitsfewergreenhousegases/lessCO
2
.
• Naturalgascombustiondoesnotemitmercury/lead/cadmium/uranium.
• NaturalgascombustionemitslessNO
x
/SO
x
/reducesacid precipitation.
• Naturalgascombustionproducesless/noparticulatematter/soot
/smog.
• Transportofnaturalgasdestroys/fragments lesshabitatorrequireslessfossilfueluse
thantransportofcoal.
•
Habitatdestruction duetotheimpoundmentofcoalashorcoalslurryisnegated.
• Coalextractiondestroyshabitatbystripminingormountaintopremoval.
1point
(c) Describeone economi
cadvantageofusingnaturalgas,ratherthancoal,inproducing
electricity.
Acceptoneofthe following:
• Transportofnaturalgas(inpipelines)costslessthantransportofcoal(byrail).
• Naturalgas(methane)harvestedfromadecompositionreaction(landfills,wastewater
treatment plants,biodigesters)costslessthancoal.
• Thereare fewerhealth‐relatedissueslinked totheburningofnaturalgasthanare
linked tobur
ningcoal,leadingtolowerhealthcarecostsforindividualsorsocietyasa
whole.
• Thereare fewerpollutioncontrolsneededforanaturalgaspowerplant,decreasing
thecostofop
eration/construction/permitting.
• Thereare lowercombustion‐residuedisposalcostsfromtheoperationofnaturalgas
burning
powerplantsthan fromcoal‐burningpowerplants.
• Natural‐gas‐burning power plantsaremuch moreefficient(moreelectricity output
fromthesam
eenergyinput)thancoal‐burning power plantsleadingtolowerfuel
costs.
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1point
AP® EnvironmentalScience2021 Scoring Guidelines
(d) Whennaturalgasisusedtoheathomes,itcanproducecarbonmonoxidegas,whichcan
leadtocarbonmonoxidepoisoninginhumans.Proposea solutiontoreducetheincidence
ofcarbonmonoxidepoisoninginhumans.
Acceptoneofthe following:
• Install/use/replace/updatecarbonmonoxidedetectors/alarms/sensorsorreplacethe
batterieswithinthesedevices.
• Performregularmaintenanceon
naturalgasfurnacestoensurethatminimal carbon
monoxideiscreatedorthatthecombustionproducts areproperly vented/exhausted
tothebuildingexterior.
• Createlawsorregulationsthatmandatethatcarbonmonoxide detectorsmustbe
installedinallhomesofa
nytype.
• UsePSA’s,billboards,orothermethodstoinform/educate thepublicaboutcarbon
monoxidepoi
soning.
• Changethehomeheating systemtoa methodthatdoesnotincludethe combustionof
afuelthatma
yproducecarbonmonoxide.
1point
(e) CalculatethepercentchangeintheaverageannualPM
2.5
concentrationintheairfrom
1990to2016.Showyour work.
Onepointforthecorrectsetup(mustincludeunitsandmultiplicationby100toyielda
truepercenta
ge)tocalculatethepercentchange:
•
3 3
(
188 μg/m — 85μg/m
)
3
* 100
85μg/m
1point
Onepointforthecorrectcalculation ofthepercentchange:
• 121%
• 120%
• 121.2%
1point
Total forpart(e) 2points
(f) TreescanremovePM
2.5
fromtheatmospherewhenparticulatessettle ontheleavesand
aresubsequentlywashedontosoilbyrain.TheaverageannualremovalofPM
2.5
is2.3
kilogramsper hectare. Calculate thedecreaseinPM
2.5
removalin kilogramsiflogging
reducedaforestedareafrom50,000hectaresto43,000hectares.Showyourwork.
Onepoint forthe correctsetup(mustincludeunits)tocalculatethenumberofkilograms
ofPM
2.5
:
•
2.3 kg
(
50, 000 ha — 43,000 ha
)
*
hectare
•
©2021CollegeBoard
50, 000 ha * 2.3 kg ha = 115, 000 kg; 43, 000 ha * 2.3 kg ha = 98,900 kg
115, 000 kg — 98,900 kg
1point
AP® EnvironmentalScience2021 Scoring Guidelines
Onepointforthecorrectcalculation ofthenumberofkilogramsofPM
2.5
:
• 16,100kilogramsofPM
2.5
• 16,000kilogramsofPM
2.5
1point
Total forpart(f)
2poi
nts
(g) Researchhasshownthat ho
spitaladmissionsforcardiovascularproblemsincrease1%with
every10%increaseinPM
2.5
concentration.Acityexperienceda23%increasein PM
2.5
concentrationandhad7,390hospitaladmissionsforcardiovascularissuesoveraone‐year
period.Calculatetheanticipatedincreaseinthenumberofhospitaladmissionsfor
cardiovascularissuesduringthenextyearifthePM
2.5
concentrationcontinuestoriseatan
identicalrate.Showyourwork.
Onepointforthecorrectsetuptocalculatetheincreaseinhospitaladmissions:
•
0.23
* 0.01 * 7, 390 admissions
0.10
•
0.23 1
* * 7,390 admissions
0.10 100
•
23%
* 1% * 7,390 admissions
10%
1point
Onepointforthecorrectcalculation oftheincrease in
hospitaladmissions.
Acceptoneofthe following:
•
169moreadmissions
• 170moreadmissions
1point
Totalforpart(g) 2points
Totalforquestion3 10points
©2021CollegeBoard