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CBSEClass10Science

SamplePaper01(2019-20)

MaximumMarks:80

TimeAllowed:3hours

GeneralInstructions:

i. Thequestionpapercomprisesthreesections–A,BandC.Attemptallthesections.

ii. Allquestionsarecompulsory.

iii. Internalchoiceisgivenineachsection.

iv. AllquestionsinSectionAareone-markquestionscomprisingMCQ,VSAtypeand

assertion-reasontypequestions.Theyaretobeansweredinonewordorinonesentence.

v. AllquestionsinSectionBarethree-mark,short-answertypequestions.Thesearetobe

answeredinabout50-60wordseach.

vi. AllquestionsinSectionCarefive-mark,long-answertypequestions.Thesearetobe

answeredinabout80–90wordseach.

vii. Thisquestionpaperconsistsofatotalof30questions.

SectionA

1. Writetheformulaandthenbalancethefollowingequation.

Ferroussulphate+Sodiumhydroxide→Ferroushydroxide+Sodiumsulphate

2. IntheModernPeriodicTable,calcium(atomicnumber20)issurroundedbyelements

withatomicnumbers12,19,21and38.Whichofthesehavephysicalandchemical

propertiesresemblingcalcium?

3. Answerthequestionsthatfollowonthebasisofyourunderstandingofthe

followingparagraphandtherelatedstudiedconcepts:

Inordertoproducehydelelectricity,high-risedamsareconstructedontheriverto

obstructtheflowofwaterandtherebycollectwaterinlargerreservoirs.Thewater

LAKSHYA STUDY POINT

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levelrisesandinthisprocess,thekineticenergyofflowingwatergetstransformed

intopotentialenergy.Thewaterfromthehighlevelinthedamiscarriedthrough

pipes,totheturbine,atthebottomofthedam.Sincethewaterinthereservoirwould

berefilledeachtimeitrains(hydropowerisarenewablesourceofenergy)wewould

nothavetoworryabouthydro-electricitysourcesgettingusedupthewayfossilfuels

wouldgetfinishedoneday.

i. Whattypeofsourceofenergyismentionedintheabovepicture?

ii. Howdoeselectricitycanbegeneratedwithahydropowerplant?

iii. Whichformofenergyofflowingofwatergetstransformed?

iv. Whydamisconstructedacrosstheriverorastream?

4. Environmentaltriggerssuchaslight,orgravitywillchangethedirectionsthatplant

partsgrowin.Thesedirectional,ortropic,movementscanbeeithertowardsthe

stimulus,orawayfromit.So,intwodifferentkindsofphototropicmovement,shoots

respondbybendingtowardslightwhilerootsrespondbybendingawayfromit.How

doesthishelptheplant?Plantsshowtropisminresponsetootherstimuliaswell.The

rootsofaplantalwaysgrowdownwardswhiletheshootsusuallygrowupwardsand

awayfromtheearth.Thisupwardanddownwardgrowthofshootsandroots,

respectively,inresponsetothepullofearthorgravityis,obviously,geotropism.If

‘hydro’meanswaterand‘chemo’referstochemicals,whatwould‘hydrotropism’and

‘chemotropism’mean?Canwethinkofexamplesofthesekindsofdirectionalgrowth

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movements?Oneexampleofchemotropismisthegrowthofpollentubestowards

ovules,aboutwhichwewilllearnmorewhenweexaminethereproductiveprocesses

oflivingorganisms.

Answerthefollowingquestions:

a. Wheredoesnegativephototropismoccursinplants?

b. Phototropisminshootsisattributedduetowhichplanthormone?

c. Tendrilsexhibit/twiningoftendrilsshowwhichtypeoftropicmovement?

d. Ifthestemgrowstowardssunlightandrootgrowsjustoppositetoit,thenwhat

typeofmovementofstemisit?

5. Whenapersonissufferingfrombothmyopiaandhypermetropia,whattype

correctivelensarerequired-

a. Convex

b. Noneofthese

c. Bifocal

d. Concave

OR

Atwhatratetheeventshouldbeprojectedtohavetheclearimage?

a. 24framespersecond

b. 20framespersecond

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c. 22framespersecond

d. 25framespersecond

6. StatementA:Groundwaterisprotectedfromcontaminationbyhumanandanimal

waste,StatementB:regionsofwaterscarcityarecloselyrelatedtotheregionsofacute

poverty

a. StatementAistrue,Bisfalse

b. BoththestatementAandBaretrue

c. StatementBistrue,Aisfalse

d. NeitherstatementAnorstatementBistrue

7. Potentialdifferencebetweenalivewireandaneutralwireis

a. 150volt

b. 220volt.

c. 210volt

d. 200volt

8. Abluelitmuspaperwasfirstdippedindil.HClandthenindil.NaOHsolution.Itwas

observedthatthecolourofthelitmuspaper

a. changedfirsttoredandthentoblue

b. changedtored

c. remainedblueinboththesolutions

d. changedfirsttoredandthentoblue

OR

Saltofastrongbaseandaweakacid

a. arebasicwithpH>7

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b. areneutralwithpH=7

c. areacidicwithpH>8

d. areacidicwithpH<7

9. Inwhichofthefollowingfoodchains,doesmangetmoreenergy?(i)Plant Man(ii)

Plant Goat Man

a. (i)Plant Man

b. (ii)Plant Goat Man

c. Noneoftheabove

d. Equalenergyin(i)&(ii)

10. Organismsofahighertrophiclevelwhichfeedonseveraltypesoforganisms

belongingtoalowertrophiclevelconstitutethe

a. Ecosystem

b. Ecologicalpyramid

c. Foodweb

d. Foodchain

11. Whichoneofthefollowingisthemostreactive?

a. Bromine

b. Iodine

c. Chlorine

d. Fluorine

12. Matchthefollowingwiththecorrectresponse:

(1)Metal (A)Acidicoxides

(2)Non-metal (B)Neutral

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(3)Amphoteric (C)Bothacidicandbasicoxides

(4)Salts (D)Basicoxides

a. 1-D,2-A,3-C,4-B

b. 1-C,2-B,3-D,4-A

c. 1-A,2-C,3-B,4-D

d. 1-B,2-D,3-A,4-C

13. Assertion:PropenereactswithHBrtogiveisopropylbromide.

Reason:AdditionofBr2toalkenetakesplaceatthefasterrateinthepresenceof

ionizingsubstance.

a. BothassertionandreasonareCORRECTbut,reasonisNOTTHECORRECT

explanationoftheassertion.

b. AssertionisINCORRECTbut,reasonisCORRECT.

c. BothassertionandreasonareCORRECTandreasonistheCORRECTexplanationof

theassertion.

d. AssertionisCORRECTbut,reasonisINCORRECT.

14. Assertion:Positivechargeinsidethecellalwaysgoesfrompositiveterminaltothe

negativeterminal.

Reason:Positivechargeinsidethecellmaygofromnegativeterminaltothepositive

terminal.

a. AssertionisINCORRECTbut,reasonisCORRECT.

b. AssertionisCORRECTbut,reasonisINCORRECT.

c. BothassertionandreasonareCORRECTbut,reasonisNOTTHECORRECT

explanationoftheassertion.

d. BothassertionandreasonareCORRECTandreasonistheCORRECTexplanationof

theassertion.

SectionB

15. Whatisefflorescence?Giveanexample?

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16. AsubstanceXusedforcoatingironarticlesisaddedtoabluesolutionofareddish-

brownmetalY.Thecolorofthesolutionfadesaway.IdentifyXandYandthetypeof

thereactioninvolved.

OR

Identifythesubstancesthatareoxidizedandthesubstancesthatarereducedinthe

followingreactions.

(i)

(ii)

17. Whydogroup1elementsformunipositiveions?

18. Whyarewhitebloodcorpusclescalledsoldiersofthebody?

OR

Namethehormonessecretedbythefollowingendocrineglandsandspecifyone

functionofeach:

a. Thyroid

b. Pituitary

c. Pancreas

19. Whatismeantbypowerofaccommodationofeye?

20. Explainspeciation.

21. Whatisreflexaction?Giveexamplesofreflexaction.

22. Namesomesourceofdirectcurrent.

23. AChildhasdrawntheelectriccircuittostudyOhm'slawasshowninFigure.His

teachertoldthatthecircuitdiagramneedscorrection.Studythecircuitdiagramand

redrawitaftermakingallcorrections.

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24. Inthefiguregivenbelow,anarrowbeamofwhitelightisshowntopassthrougha

triangularglassprism.Afterpassingthroughtheprism,itproducesaspectrumXYon

thescreen.

i. Namethephenomenon.

ii. StatethecoloursseenatXandY.

iii. Whydodifferentcoloursofwhitelightbendatdifferentanglesthroughaprism?

OR

i. Whatshouldbethepositionoftheobjectwhenaconcavemirroristobeused

a. asashavingmirrorand

b. intorchesproducingparallelbeamoflight?

ii. Amanstandinginfrontofamirror,findshisimagehavingaverysmallheadand

legsofnormalsize.Whattypeofmirrorsareusedindesigningsuchamirror?

SectionC

25. i. Howdoyouclassifyelementsintometalsandnon-metalsonthebasisoftheir

electronicconfiguration?Choosemetalandnon-metaloutofthefollowing:

ii. Whattypeofbondwillbeformedif

a. 'A'combineswith'B'?

b. 'A'combineswith'E'?

c. 'C'combineswith'E'?

d. 'D'combineswith'E'?

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26. a. Namethegasevolvedduringfermentationprocess.

b. Whatroleisplayedbyyeastintheconversionofcanesugar(C12H22O11)to

ethanol?

c. Howcanthefollowingbeobtainedfrompureethanol?Expresschemicalreactions

bythechemicalequations.

i. Sodiumethoxide

ii. Ethylethanoate

iii. Ethanal

27. Describethestructureandfunctioningofnephrons.

28. Differentiatebetweenthefollowing:

i. Pollentubeandstyle

ii. FissioninAmoebaandplasmodium

iii. Fragmentationandregeneration

iv. BudofHydraandBryophyllum

v. Vegetativepropagationandsporeformation

OR

Withthehelpofalabelleddiagramdescribedoublefertilizationinplants.

29. Aletter'A'consistsofauniformwireofresistance1ohmcm-1.Thesideoftheletter

areeach20cmlongandthecross-pieceinthemiddleis10cmlongwhileapexangle

is60o.Findtheresistanceoftheletterbetweenthetwoendsofthelegs.

30. Astudentwantstoprojecttheimageofacandleflameonthewallsofschool

laboratorybyusingalens.

i. Whichtypeoflensshouldheuseandwhy?

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ii. AtwhatdistanceintermsoffocallengthFofthelensshouldheplacethecandle

flame,soastoget

a. amagnifiedand

b. adiminishedimagerespectively,onthewall?

iii. Drawraydiagramstoshowtheformationoftheimageineachcase.

OR

Anobject2cmhighisplacedatadistanceof16cmfromaconcavemirrorwhich

producesarealimage3cmhigh.

(i)Whatisthefocallengthofthemirror?

(ii)Findthepositionoftheimage.

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CBSEClass10Science

SamplePaper01(2019-20)

Answer

SectionA

1.

Ferrous

sulphate+

Sodium

hydroxide→ Ferroushydroxide + Sodiumsulphate

FeSO4 + 2NaOH → Fe(OH)2 + Na2SO4

2. Elementswithatomicnumbers12and38havethesimilarchemicalandphysical

propertiesofcalcium.

3. i. Itisarenewablesourceofenergy.

ii. Hydropowerplantscapturetheenergyoffallingwatertogenerateelectricity.A

turbineconvertsthekineticenergyoffallingwaterintomechanicalenergy.Then

ageneratorconvertsthemechanicalenergyfromtheturbineintoelectrical

energy.

iii. Thekineticenergyofflowingwatergetstransformedintopotentialenergy.

iv. ADamisbuilttocontrolwaterthroughplacementofablockageofearth,rock

acrossastreamorriver.Theyusuallystorewaterinthereservoir,whichisthen

usedforavarietyofapplicationssuchasirrigationandmunicipalwatersupplies.

4. a. Root

b. Auxin

c. Thigmotropism

d. Positivephototropicmovement.

5. (c)Bifocal,Explanation:Bifocallensesconsistofbothconcaveandconvexlens,

upperpositionconsistoftheconcavelensandlowerportionconsistofconvexlens.

OR

(a)24framespersecond,Explanation:Framerate(expressedinframespersecond

orfps)isthefrequency(rate)atwhichconsecutiveimagescalledframesaredisplayed

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inananimateddisplay.Thehumaneyeiscapableofdifferentiatingbetween10and12stillimagespersecondbeforeitstartsjustseeingitasmotion.Thatis,atanFPSof12orless,ourbraincantellthatitsjustabunchofstillimagesinrapidsuccession,notaseamlessanimation.Oncetheframerategetsuptoaround18to26FPS,themotioneffectactuallytakeseffectandourbrainisfooledintothinkingthattheseindividualimagesareactuallyamovingscene.Thecurrentindustrystandardis24FPS.

6. (b)BoththestatementAandBaretrue,Explanation:Asthegroundwaterisstored

deepinsideitisusuallyprotectedbycontaminationofhumanandanimalwastes.

Availabilityofwaterleadstodevelopmentofaregionduetothegrowthofvarious

industries,agricultureanditsrelatedindustries.Theseprovideemploymenttothe

localpeopleandthushelptoreducepoverty.Hencewaterscarcityareclosely

correlatedtotheregionsofacutepoverty.

7. (b)220volt.,Explanation:Inourcountrythepotentialdifferencebetweenthelive

andneutralwireis220Vandthefrequencyis50Hz.

8. (d)changedfirsttoredandthentoblue

Explanation:Bluepaperturninredindicatethesampleisacidic.Bluepaperthat

doesnotchangecolorindicatesthesampleisabase.HClisacidicandNaOHisbase,

So,dil.HClturnsbluelitmusredwhichbecomesblueagaininNaOH.

OR

(a)arebasicwithpH>7Explanation:

Inaqueousmedium,strongbaseiscompletelydissociated,butweakacidisnot.

Hencesaltformedisbasic.So,itspH>7.

9. (a)(i)Plant Man,Explanation:Accordingtoanextensivestudy,10%canbetaken

astheaveragevaluefortheamountoforganicmatterthatispresentateachstep

andreachesthenextlevelofconsumers.Therefore,mangetsmoreenergyinthefirst

foodchain.Inthefirstcase,mangetsaround10%oftheenergyproducedbythe

plant.Inthesecondcase,mangetsaround1%oftheenergyproducedbytheplant.

10. NotAvailable

11. (d)Fluorine,Explanation:Ofallthehalogensgiven,Fluorineisthemostreactiveas

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thereactivityofnon-metalsdecreasesongoingdownthegroup.

12. (a)1-D,2-A,3-C,4-B,Explanation:Mostmetalsformbasicoxides.Non-metalsform

acidicoxides.Amphotericsubstanceslikezincandaluminiumformbasicoxidesas

wellasacidicoxides.Mostsaltsareneutralinnature.

13. (a)BothassertionandreasonareCORRECTbut,reasonisNOTTHECORRECT

explanationoftheassertion.Explanation:BothassertionandreasonareCORRECT

but,reasonisNOTTHECORRECTexplanationoftheassertion.

14. (a)AssertionisINCORRECTbut,reasonisCORRECT.Explanation:Assertionis

INCORRECTbut,reasonisCORRECT.

SectionB

15. Itistheprocessofthelossofmoleculesofwaterofcrystallizationfromasubstance

whenexposedtoair.Forexample:

16. ThereddishbrownmetalYisCopper(Cu)andthesubstanceusedforcoatingiron

articlesisZinc(Zn)i.e.X.

Zn(s)+CuSO4(aq) ZnSO4(aq)+Cu(s)

Thisisanexampleofasingledisplacementreactionwhereamorereactivemetal

displacesalessreactivemetalfromitssaltsolution.

OR

(i)

Inthisreaction,Naisoxidizedbecauseitcombineswith toform . is

reducedbecauseitisconvertedinto .

(ii)

Inthisreaction, isreducedbecauseitlosesoxygen. isoxidizedbecauseit

combineswithoxygenof toformwater.

17. Group1elementscontain1electronintheiroutermostshells.Theseelementslose

thiselectroneasilytoattainthe8electronsconfigurationintheiroutermostshell,to

attainstableconfiguration.Hence,theyformunipositiveion.

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18. Whitebloodcorpusclesengulf(phagocytose)theforeignmatter(bacteria,dustand

otherforeignmaterial)enteringthebodyandactasalineofdefense.Hence,WBC's

calledsoldiers.Theyproduceantibodiesagainstantigens,andantitoxinsagainst

toxins.

OR

a. ThyroidexcretesThyroxinehormone.Itregulatescarbohydrate,proteinandfat

metabolisminthebodysoastoprovidethebestbalanceforgrowth.

b. PituitaryexcretesGrowthhormone.Itregulatesgrowthanddevelopmentofthe

body.

c. PancreasexcretesInsulinhormone.Itregulatesbloodsugarlevel.

19. Theabilityoftheeyelens,toadjustitsfocallength,soastoclearlyfocustherays

comingfromdistantaswellasnearobjectsontheretina,iscalledthepowerof

accommodationoftheeye.Thisisaccomplishedbytheciliary

muscle,whichcontrolstheeye

lens,allowingittoflattenorthickenasisneededfordistantornearvision.

20. Whenenvironmentalconditionschangeorasectionofthepopulationmigratestoa

newareawithdifferentenvironmentalconditions,newspeciesmayarise.Originof

newspeciesfromtheexistingoneiscalledspeciation.Inthechangedenvironment,

populationmaybecomeadaptedordieout.Apopulationbecomesadaptedifits

individualshavesomenewtrait(geneticvariation)whichsuitsthechanged

environmentandisselectedbynatureonthisbasis.Thenewtraitspreadsby

differentialreproductionandintimebecomesastandardfeatureofasectionofthe

population.Thisistheunitofevolutionarychange.Accumulationofmanysuchunit

changesinasectionofthepopulationmaysufficientlyaltertheindividualsin

structureorfunctiontobecomeanewspecies.Thelatterarenolongerableto

interbreedwithparentalpopulation.

21. Spontaneous,mechanicalinvoluntaryresponsebyvoluntaryorganstoastimulusis

calledreflexaction.

Examplesofreflexaction:

i. Ifthehandissuddenlyprickedwithneedle,itiswithdrawnimmediately.

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ii. Wateringofmouthonlookingdeliciousdishes.

iii. Closingofeyesinresponsetosuddenflashlight.

22. Sourceofpuredirectcurrentisacell.Allotherproducefluctuatingdirectcurrent.

23. Correctdiagramisasfollows:

24. i. Thephenomenoniscalleddispersion.

ii. X—VioletY—Red

iii. Differentcoloursofwhitelightbendthroughdifferentangleswithrespecttothe

incidentbeamoflightduetodifferenceinspeedoflightofdifferentwavelengths.

OR

i. a. Objectshouldbebetweenpoleandfocus.

b. Atthefocus.

ii. a. Smallhead-convexmirror.

b. Legsofnormalsize-planemirror.

SectionC

25. i. Elementswhichcontain1to3electronsintheiroutermostshellaremetals.

Elementscontaining4to7electronsintheirvalenceshellarenon-metals.

Electronicconfigurations:

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HenceAandCaremetalswhereas,B,DandEarenon-metals.

ii. Typeofbonds

a. 'A'ismetaland'B'isnon-metal,sothebondformedwillbeionic.

A=2,8,1B=2,7

b. 'A'ismetaland'Eisnon-metal,sothebondformedisionic.

A=2,8,1B=2,7

c. 'C'ismetaland'E'isnon-metal,sothebondformedisionic.

C=2,8,2E=2,8,7

d. 'D'isanon-metaland'E'isalsoanon-metal,sothebondformedwillbe

covalent.

26. a. Thegasthatisevolvedisevolvedduringthefermentationprocessiscarbon

dioxide(CO2).Itisaccompaniedbybriskeffervescence.

b. Yeastisthesourceofenzymes-invertaseandzymase.Theseenzymesareneeded

forfermentationofcanesugar(C12H22O11)toethanol.

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Invertasehelpsinbreakingsucrose(anaturallyoccurringcarbohydratepresent

incanesugar)intoitscomponents-glucoseandfructose.

Zymaseconvertsglucoseintoalcoholandcarbondioxide.

c. Therequiredchemicalreactionsforpureethanolareasfollows:-

i. Sodiumethoxide( )canbeobtainedfrompureethanolwhenitis

madetoreactwithsodium.Sodiumdisplaceshydrogenfromethanol.

ii. Ethylethanoatecanbeobtainedfrompureethanolbywarmingethanolwith

ethanoicacidinthepresenceofconc.sulphuricacid.Thisisesterification

reaction.

C2H5OH+CH3COOH +H2O

iii. Ethanalcanbeobtainedbyperformingthepartialoxidationofpureethanolin

theabsenceofwater.Achromiumbasedreagentsuchaschromiumtrioxide

canbeused.

C2H5OH+ O2 CH3CHO+H2O

27. StructureofNephron:Nephronisthestructuralandfunctionalunitofkidney.

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i. Itconsistsofalongcoiledtubuledifferentiatedintoproximaltubule,loopofHenle

anddistaltubule.Thelatteropensintothecollectingtubule.

ii. Attheproximalendofthenephronliesadouble-walledcup-shapedstructure

calledBowman’scapsule.

iii. TheBowman’scapsulecontainsabundleofbloodcapillarieswhichiscalled

glomerulus.

iv. Intheglomerulus,thebloodthatcomesinthroughafferentarterioleisdrained

outthroughefferentarteriole.

FunctionsofNephron:

i. Filtration:FiltrationofbloodtakesplaceinBowman’scapsulefromthecapillaries

ofglomerulus.Thistakesplaceunderhighpressure.Thefiltratepassesintothe

tubularpartofthenephron.Thisfiltratecontainsglucose,aminoacids,urea,uric

acid,saltsandmajoramountofwater.

ii. SelectiveReabsorption:Asthefiltrateflowsalongthetubule,usefulsubstances

suchasglucose,aminoacids,saltsandwaterareselectivelyreabsorbedintothe

bloodbycapillariessurroundingthenephrontubule.Theamountofwater

reabsorbeddependsontheneedofthebodyandalsoontheamountofwastesto

beexcreted.

iii. Tubularsecretion:Certainsubstanceswhichareharmfulandnotneededbythe

bodylikeammonia,potassium,creatinineandhydrogenionsaresecretedfrom

thecapillarybloodintothelumenofdistaltubule.Thisiscalledtubularsecretion.

28. i. Differencesbetweenpollentubeandstyleare:

PollenTube Style

Itispartofmalegamete.Whenpollen

grainstickstoflowerstigmaatube

growingoutofpollengrainbetterknown

aspollentube.

Themiddleelongatedpartofthe

carpel,i.e.femalepartofaflower.

Whichallowspathforpollentube

togrow.

Ittransportsmalegametesfrompollen

grainstoovules.

Theattachmentofstigmatothe

ovary.

ii. Differencebetweenfissioninamoebaandplasmodiumis

FissioninAmoeba FissioninPlasmodium

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Thefissioninamoebaisbinary

fission.

Thedivisionofparentalbodyinto

twoidenticaldaughtercellsatatime.

Thus,thesizeiscomparativeto

parentcell.

Thefissioninplasmodiumismultiple

fission.

Theparentalbodydividesintonumerous

daughtercellssimultaneously.Herethe

daughtercellsarenumerousandvery

small.

iii. Differencebetweenfragmentationandregenerationis:

Fragmentation Regeneration

Themethodinwhich

multicellularorganismbreaks

upintotwoormoresmaller

fragments.

Thegrowthofawholeneworganismfrom

anyofitsbody,withthehelpofspecial

cells.i.e.singlesegmentformingnew

individual.

iv. DifferencebetweenbudofHydraandBryophyllumis:

BudofHydra BudofBryophyllum

Itisseenduringbuddingasan

outgrowthonthebodyofHydra

whichgetsfullygrownandthen

detachesfromthebodyand

becomesanewindividual.

Thisispresentontheleavesof

Bryophyllumdevelopintoanewplant

whenitcomesincontactwithsoilandother

favourableconditions.Thebudhereare

numerousinsingleleafatatime

v. Differencebetweenvegetativepropagationandsporeformationis:

Vegetativepropagation SporeFormation

Newplantsareobtainedfrom

differentpartsofparentbody

likeleaves,stems,etc.Itisa

formofasexualreproduction

thatcanbenaturalor

inducedartificially.

Sporeformationisalsoanasexualreproduction

procedurewhichoccurinnon-floweringplants.

Parentplantproducenumerousspores.Spores

whenfallonland,havetheabilitytogerminate

andproducenewfungalcoloniesunder

favourableconditions.

OR

Doublefertilization:InAngiospermsboththemalegametesarefunctional.Double

fertilizationisaprocessinwhicheggnucleusandsecondarynucleusarefertilizedat

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onetimebytwomalegameticnuclei.Thefusionofonemalegametenucleus(IN)with

eggoroosphere(IN)iscalledsyngamyandresultsintheformationofoospore(2N).

Thefusionofsecondmakenucleus(IN)withsecondarynucleus(2N)iscalledtriple

fusionwhichresultsinformationofprimaryendospermnucleus(3N).

Significance.

i. Doublefertilizationprovidesstimulustoendospermmothercellfortheformation

ofnutritivetissuenamedendosperm.

ii. Itensurescontinuedsupplyofnourishmenttotheembryothatdevelopsfrom

zygote.

29. Thearrangementofresistanceisshowninfig.(a)anditsequivalentcircuitisshown

infig(b).

Fig.(a)

Fig.(b)

Sincethewirehasaresistanceof1Ωcm-1,theresistanceofcross-piecedeis10Ω.

Sinceapexangleis600andthecross-pieceis10cm.long,theendsdandeofthe

cross-piecemustbethemid-pointofthelegsabandacsothatadebecomesan

equilateraltriangles.

Asitisclearfromthefig.daandaeareinseries.Therefore,resistanceofthe

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combinationofdaandae=10+10=20Ω.This20Ωresistanceisparalleltode.

∴Effectiveresistanceroftheportiondaedisgivenby

Nowbdandecareinserieswiththeresistanceofportiondaed.

∴Resistancebetweenbandc=10+ +10= =26.67Ω

30. i. Heshoulduseaconvexlensasrealimagesareformedbyaconvexlens,when

objectsareplacedbetweenthefocusandinfinity.

ii.

a. Formagnifiedimagecandleshouldbeplacedbetweenfocus(F)andcentreof

curvature(2F)oflens.

b. Togetdiminishedimagecandleshouldbeplacedbeyondcentreofcurvature

(2F)oflens.

iii.

a. Formagnifiedimage,(objectbetweenFand2F).

b. Fordiminishedimage,(objectbeyond2F).

OR

Sincetheimageformedisreal,henceaninvertedimageisformed.

sizeofimage,h2=-3cm,sizeofobjecth1=+2cm.

Magnification .Also

Herev=-16cm(uisalwaysnegative)

Substitutingin(i),wehavev=-(-1.5)(-16)=-24cm.orv=-24cm.

Imageisformed24cmtotheleftofthemirror(Negativesign–Imageistowardsleft

ofmirror)

Tocalculatefocallength.Hereu==16cm,v=-24cm,f=?

Using

Negativefocallengthindicatesthatthemirrorisconcave.