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2015 HIGHER SCHOOL CERTIFICATE EXAMINATION
1000
Biology
General Instructions
•Readingtime–5minutes
•Workingtime–3hours
•Writeusingblackpen
•Drawdiagramsusingpencil
•Board-approvedcalculatorsmaybeused
Total marks – 100
Section I Pages2–28
75 marks
Thissectionhastwoparts,PartAandPartB
PartA–20marks
•AttemptQuestions1–20
•Allowabout35minutesforthispart
PartB–55marks
•AttemptQuestions21–31
•Allowabout1hourand40minutesforthispart
Section II Pages29–43
25 marks
•AttemptONEquestionfromQuestions32–36
•Allowabout45minutesforthissection
–2–
Section I75 marks
Part A – 20 marksAttempt Questions 1–20Allow about 35 minutes for this part
Usethemultiple-choiceanswersheetforQuestions1–20.
1 What is the name of the theory which describes evolution as patterns of rapid firstappearancesorextinctionsfollowedbyperiodsoflittleornochange?
(A) Gradualism
(B) Convergence
(C) Adaptiveradiation
(D) Punctuatedequilibrium
2 Whatarealternativeformsofgenescalled?
(A) Alleles
(B) Autosomes
(C) Chromatids
(D) Chromosomes
3 Whichadaptationwoulddecreasewaterlossfromaplantinaregionwithlowrainfall?
(A) Broadleaves
(B) Surfaceroots
(C) Sunkenstomates
(D) Looselypackedepidermalcells
–3–
4 WhichofthefollowingdoesNOTplayaroleinmaintainingthehealthofanorganism?
(A) Mitosis
(B) Celldeath
(C) Geneexpression
(D) Sexualreproduction
5 Thediagramshowsamodelforenzymeaction.
Whichletterindicatesthesubstrateinthisdiagram?
(A) W
(B) X
(C) Y
(D) Z
6 Anextremelyhighconcentrationofcarbondioxideisundesirableinactivemuscletissuebecauseitwill
(A) increasethepH.
(B) causeenzymestodenature.
(C) increasecellularreactionrates.
(D) causehaemoglobintoreleaseoxygen.
Awaiting copyright
–4–
RefertothefollowinginformationtoanswerQuestions7and8.
Thediagramshowsahomeostaticmechanisminamammal.
Core bodytemperature
below normal
Return tonormal core body
temperatureX
Muscles of skin
Arteriole wallsin skin
NEGATIVE FEEDBACK
7 WhatdoesX representinthediagram?
(A) Theheart
(B) Thebrain
(C) Athermoreceptorintheskin
(D) Apressurereceptorinabloodvessel
8 Whichofthefollowingdescribeswhathappenstothemusclesandthearteriolewallsintheskinwhenthecorebodytemperatureisbelownormal?
Muscles of skin Arteriole walls in skin
(A) Relaxtolowerepidermalhairs Expand
(B) Contracttoraiseepidermalhairs Contract
(C) Relaxtoraiseepidermalhairs Expand
(D) Contracttolowerepidermalhairs Contract
–5–
9 Apathogenandaredbloodcellaredrawntothesamescale,withsomefeaturesindicated.
Pathogen
Cell wallMembrane
Membrane
Red blood cell
Whattypeofpathogenisthis?
(A) Avirus
(B) Aprion
(C) Afungus
(D) Abacterium
10 ATPisanorganicmoleculecommontothemetabolismofeveryspeciesonEarth.
Which of the following statements explains why this fact is considered evidence forevolution?
(A) AllspecieshaveevolvedtobesuitedtotheenvironmentofEarth.
(B) ATPmoleculesweretransferredbetweenorganismsearlyinthehistoryoflife.
(C) ThegeneforATPdeveloped in theearliestorganismsandhasbeenretainedbysubsequentspecies.
(D) All species on Earth developed the same gene for ATP as a consequence ofconvergentevolution.
11 EnvironmentcanaffectphenotypebyalteringthesequenceofbasesinDNA.
Whichofthefollowingisanexampleofthis?
(A) Highproteindietsmakingchildrentallerthantheirparents
(B) Stresscausingtheexpressionofonesetofgenesinsteadofanother
(C) Languageandmusiclessonsimprovingintelligenceinyoungchildren
(D) Nuclearfalloutfromatomicbombsincreasingbirthdefectsinpopulations
–6–
RefertothefollowinginformationtoanswerQuestions12and13.
The larvae of fruit flies damage fruit in Western Australia. To control theproblem,growersareadvisedtosprayfruittreeswithpesticides.Anyalreadydamaged fruit is boiled anddisposedof as chicken foodor landfill.Anothercontrol measure is the release of genetically engineered infertile flies of thisspecies.
12 Whichreasonbestexplainswhythecorrespondingcontrolmeasurereducesthisproblem?
Control measure Reason
(A) Releaseofinfertileflies Infertilefliesdonoteatthefruit
(B) Releaseofinfertileflies Thenumberoffliesinthenextgenerationisdecreased
(C) Boilingfruitandfeedingtochickens
Chickensareunaffectedbythedamagedfruit
(D) Boilingfruitandfeedingtochickens
Theamountofwasteforlandfillisreduced
13 The following measures could be used to prevent the spread of this fruit fly acrossAustralia.
1. Australia-widereleaseofinfertilefruitflies
2. Aerialsprayingoforchardsthroughoutthecountry
3. SpotsprayingofnewlyaffectedorchardsinWesternAustralia
4. StoppingthetransportoffruitfromWesternAustraliatootherstates
TopreventthespreadofthisfruitflyacrossAustralia,whichcombinationofmeasureswouldbemostpracticaltouse?
(A) 1and2
(B) 1and4
(C) 2and3
(D) 3and4
– 7–
14 ThetableshowsthebasetripletsinmRNAforaminoacids.
Fromthetable,theaminoacidSerine(Ser)canbecodedforbythebasetripletUCG.
Base triplets found in messenger RNA
SecondbaseU C A G
Firs
tbas
eU
Phe Ser Tyr Cys U
Thi
rdb
ase
Phe Ser Tyr Cys CPhe Ser Stop Stop APhe Ser Stop Trp G
C
Leu Pro His Arg ULeu Pro His Arg CLeu Pro Gln Arg ALeu Pro Gln Arg G
A
lle Thr Asn Ser Ulle Thr Asn Ser Clle Thr Lys Arg A
Met Thr Lys Arg G
G
Val Ala Asp Gly UVal Ala Asp Gly CVal Ala Glu Gly AVal Ala Glu Gly G
© California Department of Education
WhichbasetripletcouldcodefortheaminoacidTyrosine(Tyr)?
(A) CCU
(B) CAU
(C) UAA
(D) UAC
15 Inacertainplantspecies,individualplantshaveeitheryellow,redororangeflowers.
Twoplants,eachwithadifferentflowercolour,werecrossedinabreedingexperimentlike thosecarriedoutbyMendel.TheF2resultswere:6 red,11orangeand5yellowfloweredplants.
Whatwerethegenotypesoftheoriginalparentplants?
(A) RYandRY
(B) RRandrr
(C) RRandYY
(D) RrandRY
– 8–
16 Whymightepidemiologybeconsideredmoreessentialforthestudyofnon-infectiousdiseasesthanforthestudyofinfectiousdiseases?
(A) Thecausesofinfectiousdiseaseshavealreadybeendetermined.
(B) Onlynon-infectiousdiseasesareaffectedbypatternsofbehaviour.
(C) Epidemiologycannotbeusedtofindthecausesofinfectiousdiseases.
(D) Koch’spostulatesarenotusefulinfindingthecausesofnon-infectiousdiseases.
17 Thediagramshowsaninteractionbetweencellsoftheimmunesystem.
Antigen
Surfacereceptors
T Cell
Cytokine
Illustration from Anatomy & Physiology, Connexions Website by OpenStax College. http://cnx.org/content/col11496/1.6/, Jun 19, 2013.
Whatspecificprocessisshowninthediagram?
(A) Bcellencounteringanantigen
(B) ActivationofamacrophagebyahelperTcell
(C) StimulationofaBcelltobecomeaplasmacell
(D) CytotoxicTcelldestroyingavirus-infectedcell
18 Studentsconductedalargefirst-handinvestigationintoenzymeactivity.
Theaiminthereportisshown.
Aim: To determine the optimum pH of four different enzymes.
Howmanyindependentvariableswereinthisfirst-handinvestigation?
(A) 1
(B) 2
(C) 4
(D) 5
–9–
RefertothefollowinginformationtoanswerQuestions19and20.
Theintestinaltractofahumanfoetusissterile.
After birth, microflora from the mother are transferred to the baby’s mouththroughclosecontact.Afterayear,themicrofloraofthebabyissimilartothemother’s,withthebaby’simmunesystemignoringthesemicrobes.
Also during the first year of life, breast milk from the mother providesantibodies to the baby for any disease the mother has already experienced.Whenbreastfeedingceases,theseantibodylevelsinthebabystarttofall.
Afterthefirstyear,anynewspeciesofinvadingbacteriaistreatedasapathogenbythebaby’simmunesystem.
19 A medical consequence for six-month-old babies that have only been bottle-fed withformulamilkandnotbreastfedisthat
(A) theywillnotdevelopmicroflora.
(B) theirimmunesystemwillbedamaged.
(C) theirconsumptionofmilkcannotbequantified.
(D) theywillbeatincreasedriskofinfectiousdisease.
20 Stricthygienepracticesarefollowedinthecareofnewborns,whereashygienepracticesinthecareofolderbabiesarelessemphasised.
Whichofthefollowingisthebestreasonforthisdifference?
(A) Vaccinationsrenderpersonalhygieneunnecessaryforolderbabies.
(B) Procaryoticcellsarenotidentifiedasantigensinearlydevelopment.
(C) Antibiotictreatmentskillbacterialpopulationsinthedigestivesystem.
(D) Earlyexposuretopathogenshelpstobuildastrongimmunesystem.
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Centre Number
Student Number
–13–
43933103511001 15030
2015 HIGHER SCHOOL CERTIFICATE EXAMINATION
Biology
Section I (continued)
Part B – 55 marksAttempt Questions 21–31Allow about 1 hour and 40 minutes for this part
Answer the questions in the spacesprovided. These spaces provideguidance for the expected length ofresponse.
Extra writing space is provided onpages27and28.Ifyouusethisspace,clearly indicate which question youareanswering.
Write your Centre Number andStudent Number at the top of thispage.
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2381310356
Question 21 (2marks)
ExplainONEcontrolmeasureformalaria.
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Question 22 (2marks)
Explainwhyinsectsexcreteuricacidastheirprincipalnitrogenouswaste.
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Question 23 (3marks)
ThediagramshowsamodelinvolvingDNA.
(a) Whatprocessisbeingmodelled?
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(b) IdentifyTWOstructuralfeaturesoftheDNAmoleculewhichareNOTshowninthismodel.
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4873310354
Question 24 (7marks)
Datacanbeprovidedbyapulseoximeterpeggedtoaperson’sfinger,asshowninthediagram.
PULSE OXIMETER
97% bpm
78
(a) Whatistheoxygensaturationforthisperson?
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(b) OutlineTWOlimitationsofusingonlytheinformationprovidedinthediagramtodeterminethe‘health’ofaperson.
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(c) Explain TWO advantages in using a pulse oximeter to measure oxygensaturationcomparedtousinganothernamedtechnologyinaspecificsetting.
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7471310351
Question 25 (5marks)
Agroupofstudentswantedtotestwhetherwaterpurifyingtabletswereeffectiveinmakingcreekwaterfreefrombacteria.
They conducted an experiment using a water sample collected from the creek andfoundthatthetabletswereeffective.
(a) Describe a means of addressing ONE identified hazard relevant to thisinvestigation.
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(b) Illustratetheresultsofthisexperimentindiagrammaticform.
Uselabelstoclearlyidentifythedatacollected.
3
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9964310350
Question 26 (5marks)
Sugaristransportedinvasculartissuesinplantsandanimals.
Contrast the structure and workings of ONE named plant tissue and ONE namedanimaltissueusedtotransportsugar.
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5638310354
Question 27 (5marks)
(a) OutlineTWOdifferencesbetweenwholebloodandplasma.
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(b) ThestepsbelowshowthepreparationanduseofbloodproductsinthetreatmentofEbolaVirusDisease.Thisdiseaseischaracterisedbysignificantbloodloss.
World Health Organisation Protocol
1. ApatientrecoversfromEbolaVirusDisease.
2. Thesamepatientisdisease-freefor28days.
3. Bloodistakenfromthepatientandscreenedfortransmissiblediseases.
4. Plasmaisseparatedfromthewholeblood.
5. PlasmaistransfusedintoanotherpersonwithearlysignsofEbolaVirusDisease.
Explain why this protocol produces an effective treatment for Ebola VirusDisease.
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Use of convalescent whole blood or plasma collected from patients recovered from Ebola virus disease http://www.who.int/csr/resources/publications/ebola/convalescent-treatment/en/
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9657310359
Question 28 (5marks)
Agroupofstudentshypothesisedthattheheightofplantsdecreaseswithincreasedelevation.
Thestudentsplantedtenplantcuttingsfromthesameplantateachoffivelocations.Thelocationswereatvaryingelevationsinthesamemountainrange.Allthecuttingswere provided with the same volume of water on planting, and no fertiliser wasapplied.Thestudentsreturnedafterthesamegrowthperiodandmeasuredtheheightoftheplants.
Thecross-sectionshownindicatestheaverageheightoftheplantsinmetresafterthegrowthperiodateachlocationinthemountainrange.
1
2
3
0
Ele
vatio
n(1
02 m)
prevailing wind
Mountain range cross-section
N
(10 m) (15 m)
(4 m)
(7 m)
(12 m)
(a) Evaluatethevalidityoftheexperiment.
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6157310351
Question28(continued)
(b) Completebothcolumnsofthetabletobestpresentthedatafortheanalysisofanytrend.
End of Question 28
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Question 29 (6marks)
‘The application of modern reproductive techniques in plant and animal breedinglimitsgeneticdiversity.’
Discussthisstatement.
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6784310357
BLANKPAGE
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7927310357
Question 30 (7marks)
Thegraphshowsthehistoryoftherelativenumbersofthreevarietiesofbird(X,YandZ )withinabirdspecies,onaremoteislandinthePacificOcean.
Thebirdspeciesarrivedontheislandinamigrationevent.Beforemigration,thebirdspecieswasnotpresentontheisland.
Thegraphrecordofbirdnumbersontheislandisdividedintotwosections(1and2).Overthetimedatawererecorded,theenvironmentoftheislanddidnotchange.
0 50 100Time (Number of generations after migration event)
Num
ber o
f bird
s
Variety X
Variety Y
Variety Z
150 200
21
(a) Whatbirdvarietiesoriginallymigratedtotheisland?
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9403310358
Question30(continued)
(b) Using the Darwin/Wallace theory of evolution, and making reference(s) to thedatainthegraph,explainthechangestothepopulationofeachvarietyofbirdin
(i) section 1 ofthegraph. 2
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(ii) section 2 ofthegraph.
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Question 31 (8marks)
‘Renal dialysis and kidney transplants are very different treatments for the samemedicalcondition.Eachtreatmentwasdevelopedfromanewapplicationofbiologicalknowledge.’
Justifythesestatements.
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9248310355
Section I Part B extra writing space
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8455310354
Section I Part B extra writing space
If you use this space, clearly indicate which question you are answering.
© 2015 Board of Studies, Teaching and Educational Standards NSW
–29–1002
2015 HIGHER SCHOOL CERTIFICATE EXAMINATION
Biology
Section II
25 marksAttempt ONE question from Questions 32–36Allow about 45 minutes for this section
Answerparts(a)–(e)ofonequestionintheSectionIIWritingBooklet.Extrawritingbookletsareavailable.
Pages
Question32 Communication......................................................................30–31
Question33 Biotechnology........................................................................33–35
Question34 Genetics:TheCodeBroken?.................................................37–39
Question35 TheHumanStory.................................................................. 40–41
Question36 Biochemistry..........................................................................42–43
– 30–
Question 32 — Communication (25marks)
Answerparts(a),(b)and(c)ofthequestiononpages2–4oftheSectionIIWritingBooklet.Starteachpartofthequestiononanewpage.
(a) Thediagramshowschangesinmembranepotentialinaneuroneafterastimulusisappliedattimet.
t
–70
–60
+30
Time (ms)
Mem
bran
e po
tent
ial (
mV
)
Adapted from Art Connection graph: Figure 3. http://cnx.org/contents/72cfcf6f-e196-4e0b-9bcf-45f4853993e4@5/How-Neurons-Communicate
(i) Whatistherestingmembranepotentialofthisneurone? 2
(ii) With reference to this diagram, explain why some stimuli would notgenerateanactionpotentialinaneurone.
2
(b) Differentspeciesofanimalscanseethesameenvironmentdifferently.
Explainthisintermsofthewavelengthsoftheelectromagneticspectrumthatanimalscandetect.Usespecificexamplesinyouranswer.
4
(c) Account for the diversity of senses in humans, in terms of receptors andcorrespondingregionsofthebrain.SupportyouranswerwithTWOexamples.
4
Question 32 continues on page 31
– 31–
Question32(continued)
Answer parts (d) and (e) of the question on pages 6–8 of the Section II WritingBooklet.Starteachpartofthequestiononanewpage.
(d) Asoundshadowisproducedwhenthewavelength(l)ofasoundisshorterthanthelengthofthehumanhead(l).Whenasoundofwavelengthlongerthantheheadisused,nosoundshadowoccurs.SeeFigure1.
l<
l>
0.25
0.50
0.75
1.00
1.75
2.00
1.25
1.50
0 1000 2000Frequency (Hz)
3000 4000 5000
Wav
elen
gth
(m)
Figure 1
Figure 2
(i) Predictadifferenceintheloudnessofthesoundineachearifthesoundhasawavelengthshorterthanthelengthofthehead.Justifyyouranswer.
2
(ii) Aperson’sheadis25cmlong.UsingFigures1and2,andshowingthe steps, determine the frequency range of sound for which a soushadowoccursforthisperson.
allnd
4
(e) ‘Scienceisusedtosolveproblemsforthebenefitofsociety.’
JustifythisstatementwithreferencetothescientificknowledgeusedtosolveONEprobleminhearingandONEprobleminvisualaccommodation.
7
End of Question 32
©Thomas Haslwanter
–33–
Question 33 — Biotechnology (25marks)
Answerparts(a),(b)and(c)ofthequestiononpages2–4oftheSectionIIWritingBooklet.Starteachpartofthequestiononanewpage.
(a) Thefermentationreactionshownoccursasyeastbiomassincreases.
Glucose X + Y
(i) IdentifytheproductsXandY. 2
(ii) Describehow,after the18thcentury, the fermentationofglucosewasmodifiedtoincreasetheyieldofyeastbiomass.
2
(b) DNAcanbeextractedinaschoollaboratory.
Describeseparatelythemethodusedtoget theDNAoutof thecells,andthemethodusedtoisolatetheDNAfromothercellcomponentsinthissetting.
4
(c) Explain why the domestication of species for agriculture is described as abiotechnology.Inyouranswer,refertoONEspecificdomesticatedorganism.
Question 33 continues on page 34
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–34–
Question33(continued)
Answer parts (d) and (e) of the question on pages 6–8 of the Section II WritingBooklet.Starteachpartofthequestiononanewpage.
(d) (i) Whyislacticacidfermentationusedinthetransformationofmilkintocheese?
2
(ii) Severalgroupsofstudentsinaclassinvestigatedtheoptimumconditionsfor the transformation of milk into cheese using a common bacterialstarterculture.
Each group conducted experiment 1 and the class obtained averagevaluesof their results.Theclass thendesignedexperiment2andeachgroupconductedtheexperiment,againobtainingaveragevaluesoftheirresults.Theaveragevaluesforeachexperimentareshownbelow.
4
Experiment 1–The effect of temperature on lactic acid production inmilkatpH5
Time after bacteria added
(hours)
Average lactic acid concentration in substrate
(%)Fermentationtemperature
2°C
Fermentationtemperature
25°C
Fermentationtemperature
35°C
0 0.1 0.1 0.1
10 0.1 0.2 0.2
20 0.1 0.3 0.2
30 0.2 0.8 0.4
40 0.3 1.8 0.7
50 0.4 2.2 1.0
60 0.6 2.3 1.3
Question 33 continues on page 35
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Question33(continued)
Experiment 2–TheeffectofpHonlactoseconversioninmilkat25°C
1
1.5
2
2.5
4
4.5
3
3.5
0 20 40
Time (hours)
60
pH 8
pH 5
pH 2
Aver
age
Lact
ose
Con
cent
ratio
n (%
)
Thestudentsconcludedthattheresultswerecontradictoryandthattheycouldnotdefinetheoptimumconditionsfortheircheeseproduction.
Evaluatethestudents’conclusionwithreferencetotheirdatafrombothexperiments.
(e) ‘Scienceisusedtosolveproblemsforthebenefitofsociety.’
Justify this statement with reference to the scientific knowledge behindDNAtechnology,usingONEexamplefrommedicineandONEfromforensics.
7
End of Question 33
–37–
Question 34 — Genetics: The Code Broken? (25marks)
Answerparts(a),(b)and(c)ofthequestiononpages2–4oftheSectionIIWritingBooklet.Starteachpartofthequestiononanewpage.
(a) Thediagramshowstwocellstakenfromthesameorganism.
(i) WhattypeofcellisCell B? 1
(ii) Explain the potential effects on this species of a disadvantageousmutationineachofthesecelltypes.
3
(b) Describe how the current models of the structure of tRNA and mRNA havehelpedusunderstandtheproductionofasequenceofaminoacids.
4
(c) Describehowtheactionofgenescanexplainfeaturesofembryonicdevelopment.
Question 34 continues on page 38
4
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–38–
Question34(continued)
Answer parts (d) and (e) of the question on pages 6–8 of the Section II WritingBooklet.Starteachpartofthequestiononanewpage.
(d) A biology class searched the internet for published results of cross-breedingexperimentsonthesamethreetraitscontrolledbygenesknowntobelinked.
Theyfoundtwobreedingexperimentsonthesamespeciesoffloweringplant,involvingthegenesforstamenlength,flowercolourandfruitcolour.
Eachexperimentinvestigatedtwoofthethreegenes.Theexperimentalresultswerepresentedindifferentformats.
Experiment 1: AaEe × aaee
Raw data: Phenotypicratiosinoffspring
–27longstamen,redflowers
–3longstamen,yellowflowers
–3shortstamen,redflowers
–27shortstamen,yellowflowers
Experiment 2: BbEe × bbee
After data analysis: Resultindicatedonareferencegraph.
5
0
10
15
20
25
0 5 10
Distance between genes (map units)
15 20 25
Deg
ree
of re
com
bina
tion
(%)
Question 34 continues on page 39
–39–
Question34(continued)
The class concluded that the distance between Gene A and Gene E is less than thedistancebetweenGeneBandGeneE.
(i) Show,withworking,thatGeneAis10mapunitsfromGeneE. 2
(ii) Evaluatetheconclusionsdrawnbytheclass. 2
(iii) Whatfurtherdatawouldneedtobecollectedtodrawaquantitativemapof the chromosome showing the relative positions of all these genes?Justifyyouranswer.
2
(e) ‘Scienceisusedtosolveproblemsforthebenefitofsociety.’
Justify this statement with reference to the scientific knowledge behindDNAtechnology,usingONEexamplefrommedicineandONEfromforensics.
7
End of Question 34
– 40–
Question 35 — The Human Story (25marks)
Answerparts(a),(b)and(c)ofthequestiononpages2–4oftheSectionIIWritingBooklet.Starteachpartofthequestiononanewpage.
(a) (i) Thediagramshowstwoprimates. 2
BIOZONE, Human Evolution OHT Masters Set No. 8, 1998, BIOZONE International. Reproduced with permission
Provide the word that describes the tail for the classification of eachprimate.
(ii) Spider monkeys and baboons are members of the same order. Usethe hierarchical classification system to explain whether they wouldnecessarilybeinthesamephylumandthesamegenus.
2
(b) Explain ONE piece of evidence for, and ONE piece of evidence against, thetheoryofregionalcontinuity.
4
(c) Account for identified differences in the cultural development ofAustralopithecines and Homo neanderthalensis in relation to their cranialcapacities.
Question 35 continues on page 41
4
Figure 1 Figure 2
Spider monkey Baboon
–41–
Question35(continued)
Answer parts (d) and (e) of the question on pages 6–8 of the Section II WritingBooklet.Starteachpartofthequestiononanewpage.
(d) (i) Distinguishbetweenrelativedatingandabsolutedatingoffossils. 2
(ii) Studentsfoundthreefossils(A,BandC)atanarchaeologicalsite. 4
Thedepthofeachfossilbelowthesurfacewasrecordedandthestrataofrocksatthesiteweremapped.
Figure 1
Figure 2
Number of half-lives
Fossil C
Fossil B
Fossil A
0 1 2 3 4 5
0
20
40
Dep
th (m
)R
atio
of C
14: C
12
livingtree
A
C
B
××
×
×
×
×
ThefossilswereanalysedinthelaboratoryforratiosofC14toC12,andtheresultswerepresentedonaC14half-lifecurve.
Figure 1
Figure 2
Number of half-lives
Fossil C
Fossil B
Fossil A
0 1 2 3 4 5
0
20
40D
epth
(m)
Rat
io o
f C14
: C12
livingtree
A
C
B
××
×
×
×
×
Thestudentsconcludedthattheirdatawereconflictingandtheycouldnotdeterminetherelativeagesofthefossils.
Evaluatethestudents’conclusionwithreferencetothedatapresented.
(e) ‘Sciencehasbeenusedtosolveproblemsintheinvestigationofevolutionaryrelationships between humans and other primates, and so has providedinformationofinteresttosociety.’
JustifythisstatementintermsofthescientificknowledgebehindDNA–DNAhybridisationANDkaryotypeanalysis.
7
End of Question 35
–42–
Question 36 — Biochemistry (25marks)
Answerparts(a),(b)and(c)ofthequestiononpages2–4oftheSectionIIWritingBooklet.Starteachpartofthequestiononanewpage.
(a) (i) Thediagramshowsamodelofaphotosyntheticunit. 1
WhatisanappropriatelabelforthecomponentsX?
(ii) ExplainwhyhavingphotosystemIandphotosystemIIacting togetherincreasestheefficiencyofphotosynthesis.
3
(b) From their experiments, Blackman and Mathgel hypothesised thatphotosynthesiswasatwo-stepprocessasfollows:
lightdependentreaction
temperaturedependentreaction
4
Explain how their results led them to hypothesise that photosynthesis beginswithalightdependentreaction.
(c) Explain the location of the light and dark reactions within the chloroplast,withreferencetoaspecificfeatureoftheorganelleateachlocation.
Question 36 continues on page 43
4
Awaiting copyright
–43–
Question36(continued)
Answer parts (d) and (e) of the question on pages 6–8 of the Section II WritingBooklet.Starteachpartofthequestiononanewpage.
(d) (i) Outlinehowpigmentscanbeextractedfromleaves. 2
(ii) Studentsinvestigatedthepigmentsintheleavesofanewly-discoveredplant,andcomparedtheirresultstoresultsfromexperimentsonknownpigmentsfromafamiliarplant.Allexperimentalresultsareshown.
4
Distance travelled
(cm)
New plantFamiliar plant
Results of chromatography with the same solvent
Solvent front
Dark green lineLight green line
5.0
4.252.89
Pigment
Chlorophyll b
Chlorophyll a
Distance travelled by
pigment(cm)
Distance travelled by
solvent(cm)
6.2
9.1
10.7
10.7
Thestudentsconcludedthatthenewplanthasauniquepigmentsystem.
Evaluatethestudents’conclusionwithreferencetothedatapresented.
(e) ‘Sciencehasbeenusedtosolveproblemsintheinvestigationofphotosynthesis,andsohasprovidedinformationofbenefittosociety.’
Justify this statement with reference to the scientific knowledge behindradioactivetracersforthestudyofphotosynthesis.
7
End of paper
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