2021
AP
®
Environmental
Science
Sample Student Responses
and Scoring Commentary
Set 2
Inside:
Free Response Question 1
• • Scoring Guideline
• • Student Samples
• • Scoring Commentary
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AP®EnvironmentalScience2021ScoringGuidelines
©2021CollegeBoard
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r
elationshipbetweenslopeandannualerosionrateforfourdifferentland
usetypes?
• Doescroprotation/tilling/nottilling/usingcovercropsonvariousslopes
increase/decrease/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).
1point
AP®EnvironmentalScience2021ScoringGuidelines
©2021CollegeBoard
(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data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hypothesis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matures.
• 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their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causing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,whichcandecreasetheviabilityoftheeggs
that
havealreadybeenlaid.
• Sedimentcanincreasewaterturbidity,whichdecreasesfishnavigation/abilityto
forage/efficiencyofoxygenusewhichdecreasestheamountofeggslaid.
1point
Totalforpart(c) 2points
Totalforquestion1 10points
1A 1 of 2
1A 2 of 2
1B 1 of 2
1B 2 of 2
1C 1 of 2
1C 2 of 2
AP
®
Environmental Science 2021 Scoring Commentary
© 2021 College Board.
Visit College Board on the web: collegeboard.org.
Question 1
Note: Student samples are quoted verbatim and may contain spelling and grammatical errors.
Overview
The intent of this question was for students to demonstrate their ability to identify components of a scientific
experiment and to explain concepts related to agricultural practices and soil erosion. Students were expected
to convey an understanding of the sedimentation of waterways.
In part (a) students were expected to demonstrate their ability to answer questions about the effect of four
common agricultural practices on the annual soil erosion rates at various land slopes based on data provided
in a graph [Practice 5-Data Analysis, Practice 1-Concept Explanation, Topic 5.4 Impacts of Agricultural
Practices]. In part (b) students were asked to identify and evaluate various parts of an experiment focused on
decreasing sediment run-off from disturbed land [Practice 4-Scientific Experiments, Topic 4.2 Soil Formation
and Erosion, Topic 8.2 Human Impacts on Ecosystems]. In addition, after being presented with data from the
experiment, students were asked to make a claim about a presented hypothesis. In part (c) students were asked
to describe the survivorship curve of fish species living in streams affected by sediment [Topic 3.3
Survivorship Curves] and asked to explain the effects of sediment run-off on the reproductive ability of these
fish [Practice 7-Environmental Solutions, Topic 8.2 Human Impacts on Ecosystems].
Sample: 1A
Score: 10
One point was earned in part (a)(i) for identifying the scientific question “what is the effect of percent slope on
annual erosion for four agricultural practices?” One point was earned in part (a)(ii) for identifying “crop rotation”
as the agricultural practice. One point was earned in part (a)(iii) for describing “no till with cover crop is much
more effective at reducing soil erosion than no-till by itself.” One point was earned in part (a)(iv) for identifying
“rainfall” as a natural mechanism of soil erosion. One point was earned in part (b)(i) for identifying “the amount
of sediment run-off” as the dependent variable. One point was earned in part (b)(ii) for describing one way to
“add a control group [is] by getting a third plot of land near a road under construction and not putting any method
to reduce run-off there.” One point was earned in part (b)(iii) for identifying “the slope of the different plots” as
one variable that was not discussed that could affect the results of the study. One point was earned in part (b)(iv)
for making a claim that “the stated hypothesis is incorrect because the straw bales do not reduce more sediment
run-off than planted grass does.” The response supports the claim with “the planted grass was more effective
because it took 28 cm until the object couldn't be seen in comparison with only 12 cm for the straw bale plots.”
One point was earned in part (c)(i) for describing “fish lay several (hundreds) of eggs at a time and ... they display
a Type III survivorship curve with very few surviving initially, a [population] drop down, and then a stabilizing of
the ones that do survive.” One point was earned in part (c)(ii) for explaining, “An increase in sediment equals an
increase in turbidity [which] means there is less albedo so the water absorbs more sun and ... the temperature
increases. Warmer waters have less dissolved oxygen and ... fish may not be healthy enough to reproduce, due to
a lack of oxygen.”
AP
®
Environmental Science 2021 Scoring Commentary
Question 1 (continued)
Sample: 1B
Score: 6
One point was earned in part (a)(i) for identifying the scientific question “how does the slope of an area and
tillage practice affect the amount of soil erosion?” One point was earned in part (a)(ii) for identifying “Crop
rotation” as the agricultural practice. One point was earned in part (a)(iii) for describing, “The addition of a cover
crop as compared to a no till with no cover crop leads to ... less soil erosion.” No point was earned in part (a)(iv).
One point was earned in part (b)(i) for identifying “the amount of sediment discharge” as the dependent variable.
One point was earned in part (b)(ii) for describing “A way to add [a] control to the study is to measure a third plot,
which has no treatment of erosion prevention.” One point was earned in part (b)(iii) for identifying “one variable
that could affect the results is the location of each plot ... because ... both plots ... may not be on the same slope.”
No point was earned in part (b)(iv). No point was earned in part (c)(i). No point was earned in part (c)(ii).
Sample: 1C
Score: 3
One point was earned in part (a)(i) for identifying the scientific question “What are the effects of different
agricultural practices and slopes on annual erosion rates.” One point was earned in part (a)(ii) for identifying
“Crop rotation” as the agricultural practice. One point was earned in part (a)(iii) for describing, “When adding a
cover crop, anual erosion decreases compared to using the no-till method.” No point was earned in part (a)(iv). No
point was earned in part (b)(i). No point was earned in part (b)(ii). No point was earned in part (b)(iii). No point
was earned in part (b)(iv). No point was earned in part (c)(i). No point was earned in part (c)(ii).
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