ALBIOLOGYPAPER1+2.docx

ALBIOLOGYPAPER1+2.docx

《ALBIOLOGYPAPER1+2.docx》由会员分享，可在线阅读，更多相关《ALBIOLOGYPAPER1+2.docx（16页珍藏版）》请在冰豆网上搜索。

ALBIOLOGYPAPER1+2

2000Biology

Paper1A

SectionA

AnswerALLquestions.

AnswersshouldhewrittenintheAL（C）lAnswerBook.

Beginyouranswertoeachquestion（notthesub-partofaquestion）onaseparatepageintheanswerbook.

1.Nametwoorganellesthatarefoundabundantlyinmammalianlivercells.Relatetheirabundancetothefunctionsofthelivercells.

（4marks）

[CellBiology]

2.Thefollowingflowchartsshowthestagesofgameteformationinfloweringplantsandmammals.Statethetypeofnucleardivisioninvolvedineachoftheprocesses（a）,（b）,（c）and（d）.

（2marks）

FloweringplantsMammals

microsporemothercell（2n）germcell（2n）

（c）

（a）

microspore（pollengrain）spermatogonium

（d）

（b）

malegametesperm

[Reproduction]

3.PhotomicrographsP,QandRontheoppositepageshowastructureatdifferentdevelopmentalstagesobservedinamammalianorgan.Theyarenotarrangedaccordingtothesequenceofdevelopmentofthisstructure.

（a）Showthecorrectsequenceofdevelopmentofthestructurebylistingthelettersofthephotomicrographs.

（1mark）

（b）Thenormaldevelopmentofthestructurecanbeartificiallyinterrupted.Suggestonewaytobringaboutthisinterruptionandexplainthemechanisminvolved.

（4marks）

（c）NamethestructureinPandstateitsfunction.

（2marks）

PhotomicrographP（×40）PhotomicrographQ（×75）

PhotomicrographR（×120）

[Growth]

4.Whichofthefollowinggraphsrepresentsthegrowthpatternofariceplant?

Explainyouranswer.

（2.5marks）

[Growth]

5.Thekeybelowcanbeusedtoidentifytheechinodermspeciesillustratedontheoppositepage.

1aPossessastalk,sessileCenocrinusasterias

1bLackastalk,notsessile2

2aNoarms6

2bArmspresent3

3aArmssharplymarkedofffromthecentraldisc4

3bArmsnotsharplymarkedofffromthecentraldisc5

4aFivepairsofshieldsoncentraldiscOphiothrixfragilis

4bCentraldiscwithoutshieldsOphiarachnaincrassata

5aLongarmswithrelativelysmallcentraldiscArchastertypicus

5bShortarmswithrelativelylargecentraldiscRosasteralexandri

6aCushion-shaped,withmanyspines7

6bElongatedinshape,withoutspinesThyonellagemmata

7aLong,fine,andsharpspinesLytechinusvariegatus

7bThickandpen-shapedspinesHeterocentrusmammilatus

（a）Usingthiskey,identifytheechinodermsD,FandHshownontheoppositepage.Ineachcasestatethekeysequenceyouwouldgothroughinmakingtheidentification.

（3marks）

（b）StatethescientificnameofspeciesAandthegenusnameofspeciesB.

（2marks）

（c）WheredoyouexpecttofindthelocomotoryorgansofD?

（1mark）

[Classification]

6.Yeastproducesanextracellularinvertasetobreakdownsucroseintoglucoseandfructose.Designanexperimenttoshowthepresenceofextracellularinvertaseactivitiesinayeastcultureandstatetwoappropriatecontrols.

（7marks）

[Enzymes]

7.Mammalslivingindesertsarefoundtohaveawell-developedposteriorlobeofthepituitary.Explainhowthisfeatureenablessuchmammalstoadaptforsurvivalindeserts

（4marks）

[Hormones]

8.Thefollowingphotomicrographwastakenunderalightmicroscopeshowingthelarvalstageofamarinecrab:

（a）Makea2wholespecimendrawingtoshowthefeaturesofthelarva.

（5marks）

（N.B.YouareNOTrequiredtolabelthefeaturesorgiveatitletoyourdrawing）

（b）Onyourdrawing,useanarrow/arrowstopointtotheappendage（s）thatyouthinkis/arelocomotoryinfunction.

（0.5mark）

（c）Givetwowaysinwhichthislarvalstageissignificanttothemarinecrab.

（2marks）

[Growth]

Paper1B1

AnswerALLquestions.

TherearetwoquestionsinthisQuestion-Answerbook.Theydonotcarryequalmarks.

Putyouranswerinthespacesprovided.

9.（a）Figure1showsastandardcurveobtainedbyusingacolorimetricmethodfordeterminingtheconcentrationofproteinsolutions.

Inanexperimenttostudytheeffectofheattreatmentonthedigestibilityofaproteinsubstrateandtheeffectofrawbeanextract（takenfrombeanX）onproteaseactivity,variousreactionmixtureswerepreparedandwereincubatedfor30minutes.Theproteinconcentrationofeachreactionmixtureatthebeginningandattheendoftheincubationperiodwasdeterminedbythecolorimetricmethod.IntensitiesofcolourdevelopedareshowninTable1.

Table1

Incubationperiod/min

Colourintensityofthereactionmixtures/arbitraryunit

Heatedproteinsubstrate+protease

Unheatedproteinsubstrate+protease

Unheatedproteinsubstrate+rawbeanextract+protease

0

10

10

10

30

4

7

9

（N.B.Theproteincontentoftherawbeanextractaddedisnegligible.）

（i）UsethecurveshowninFigure1todetermine

（1）theproteinconcentrationofthereactionmixturesatthebeginningoftheincubationperiod

（0.5mark）

（2）theproteinconcentrationofthefollowingreactionmixturesafterdigestionbytheproteasefor30minutes:

mixturewiththeheatedproteinsubstrate

mixturewiththeunheatedproteinsubstrate

（1mark）

（ii）Whichismoredigestiblebytheprotease,theheatedortheunheatedsubstrate?

Justifyyourchoicebyinterpretingtheexperimentaldata.

（1.5marks）

（iii）Basedonthestructureofproteinmolecules,accountfortheeffectofheattreatmentonthedigestibilityofthisproteinsubstrate.

（3marks）

（iv）Whatistheeffectoftherawbeanextractonproteaseactivity?

（0.5mark）

（b）Inanotherexperiment,dienutritivevalueofbeanswasstudied.Ratswerefedwithdietspartlyreplacedwitheitherrawbeanflourorheatedbeanflour.Theaverageinitialbodymassoftheratswas80gperrat.After30days,theaveragebodymassesoftheratswererecorded.Thetotaldietaryproteinintakeoftheratsduringdieexperimentwasdetermined.TheresultsareshowninTable2.

Table2

Diet

Totaldietaryproteinintakeperrat/g

Averagebodymassperrat/g

A.Controldiet

40.0

295

B.Dietpartlyreplacedwithrawbeanflour

36.2

253

C.Dietpartlyreplacedwithheatedbeanflour

39.5

328

（N.B.Theproteincontentsofdiethreedietswerediesame.ThebeanflourusedwasobtainedfrombeanX.）

（i）Thenutritivevalueofaproteindietcanbemeasuredbyitsproteinefficiencyratio（PER）.PERisdefinedasdiegaininbodymassofthetestedanimalpergramdietaryproteinintake.CalculatethePERofthefollowingdietsandcompleteTable3.

Table3

Diet

PER

A.Controldiet

5.38

B.Dietpartlyreplacedwithrawbeanflour

C.Dietpartlyreplacedwithheatedbeanflour

（2marks）

（ii）BasedondieabovePERvalues,whichdietismostnutritive?

（1.5mark）

（iii）Compareandaccountfordiedifferenceinnutritivevaluebetweenthefollowingdiets.

（1）dietsAandB（1.5marks）

（2）dietsBandC（2.5marks）

Total:

13marks

[Enzymes]

10.Adiploidplantspeciesiscapableofbothselfandcrosspollination.Twopurebredvarieties,YandZ,ofthisplantspecieswereidentified.IndividualsofvarietyYhaveheightsrangingfrom21-25cm.Theyallhaveroundleavesandareresistanttotheherbicideglyphosate.IndividualsofvarietyZhaveheightsrangingfrom56-60cm.Theyallhavewrinkledleavesandaresensitivetotheherbicideglyphosate.WhenYwascrossedwithz,allF1progenyhadroundleavesandwereglyphosateresistant.TheirheightdistributionisshowninTable1.

Table1

Height/cm

Numberofplants

26-30

2

31-35

10

36-40

54

41-45

51

46-50

8

51-55

3

WhentheF1plantswereself-pollinated,theF2progenyhadthefollowingphenotypes:

Table2

Height/cm

Numberofplants

Roundleafand

Resistanttoglyphosate

Wrinkledleaf

and

Resistanttoglyphosate

Roundleaf

and

Sensitivetog1yphosate

Wrinkledleaf

and

Sensitivetoglyphosate

21-25

15

1

0

5

26-30

88

2

2

28

31-35

114

4

3

35

36-40

152

5

5

48

41-45

152

5

6

47

46-50

116

4

4

36

51-55

86

2

3

27

56-60

13

0

0

4

Sub-total

736

23

23

230

（a）Aretheallelesresponsibleforwrinkledleavesandglyphosateresistancedominantorrecessive?

Brieflyexplainyouranswer

（3marks）

（b）Howmanygenescontroltheglyphosateresponse?

ExplainyouranswerwithreferencetothedatashowninTable2.

（4marks）

（c）（i）DiscusswhethertheinheritanceofleafshapeandglyphosateresponsefollowsMendel'sLawofIndependentAssortment.

（4.5marks）

（ii）Whatistherelationshipbetweenthegenescontrollingleafshapeandglyphosateresponse?

（1mark）

（d）BasedonthedatashowninTablesIand2,stateandexplainthenatureofgeneticcontrolofheightinthisplantspecies.

（4marks）

[Genetics]

AnswerALLquestions.

TherearetwoquestionsinthisQuestion-Answerbook.Theydonotcarryequalmarks.

Putyouranswersinthespacesprovided.

11.AnexperimentwasconductedtoinvestigatetheeffectofplantextractEontheplasmaglucoselevelofnormalrats.

（a）Twogroupsofnormalratswerefasted（notgivenanyfood）overnight.Afterfasting,Ewasadministeredtoonegroup.Thenbothgroupsofratsweregiventhesameoraldoseofglucosesolution.Figure1showstheirplasmaglucoselevelsatvarioustimeintervals

Figure1

（i）WhatistheimportanceoffastingtheratsovernightbeforetheadministrationofE?

（2marks）

（ii）Inthisexperiment,plasmahastobepreparedfromthebloodsampleaftercollectionassoonaspossible,otherwiseachangeofplasmaglucoselevelwouldresult.Whywouldtherebesuchachange?

（1mark）

（iii）Accountfortheriseandsubsequentfallinplasmaglucoselevelinthecontrolrats.

（4.5marks）

（iv）StatetheeffectofEonplasmaglucoselevelSuggesttwopossiblewaysinwhichEmighthaveproducedthiseffect.

（2.5marks）

（b）InordertostudyhowEproducesitseffect,afurther