Exercise Multiple Choice Questions (MCQs)...Chapter 6 Life Processes Multiple Choice Questions (MCQs) 1.Which of the following statements about the autotrophs is incorrect? (a)They

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CBSEClass10Science

NCERTExemplarSolution

Chapter6

LifeProcesses

Multiple Choice Questions (MCQs)

1. Whichofthefollowingstatementsabouttheautotrophsisincorrect?

(a) Theysynthesisecarbohydratesfromcarbondioxideandwaterinthepresenceofsunlight

andchlorophyll

(b) Theystorecarbohydratesintheformofstarch

(c) Theyconvertcarbondioxideandwaterintocarbohydratesintheabsenceofsunlight

(d) Theyconstitutethefirsttrophiclevelinfoodchains

Ans.(c)Theyconventcarbondioxideandwaterintocarbohydratesintheabsenceof

sunlight.

2. Inwhichofthefollowinggroupsoforganisms,foodmaterialisbrokendownoutside

thebodyandabsorbed?

(a) Mushroom,greenplants,Amoeba

(b) Yeast,mushroom,breadmould

(c) Paramecium,Amoeba,Cuscuta

(d) Cuscuta,lice,tapeworm

Ans.(b)Yeast,mushroom,breadmould

Explanation:Allofthemaresaprotrophs.Insaprotrophicmodeofnutrition,foodmaterial

isbrokendownoutsidethebodyandabsorbed.

Exercise


3. Selectthecorrectstatement

(a) Heterotrophsdonotsynthesisetheirownfood

(b) Heterotrophsutilisesolarenergyforphotosynthesis

(c) Heterotrophssynthesisetheirownfood

(d) Heterotrophsarecapableofconvertingcarbondioxideandwaterintocarbohydrates

Ans.(a)Heterotrophsdonotsynthesisetheirownfood.

Explanation:Heterotrophsdependonotherorganismsforfood.

4. Whichisthecorrectsequenceofpartsinhumanalimentarycanal?

(a) Mouth→stomach→smallintestine→oesophagus→largeintestine

(b) Mouth→oesophagus→stomach→largeintestine→smallintestine

(c) Mouth→stomach→oesophagus→smallintestine→largeintestine

(d) Mouth→oesophagus→stomach→smallintestine→largeintestine

Ans.(d)Mouth→oesophagus→stomach→smallintestine→largeintestine

5. Ifsalivaryamylaseislackinginthesaliva,whichofthefollowingeventsinthemouth

cavitywillbeaffected?

(a) Proteinsbreakingdownintoaminoacids

(b) Starchbreakingdownintosugars

(c) Fatsbreakingdownintofattyacidsandglycerol

(d) Absorptionofvitamins

Ans.(b)Starchbreakingdownintosugars(maltoseandisomaltose)

Explanation:Salivaryamylaseconvertsstarchintosugar.Digestionofproteinsandfats

https://www.ncertbooks.guru/ncert-exemplar-problems-solutions-pdf/


doesnottakeplaceinmouth,henceoptions(a)and(c)areincorrect.

6. Theinnerliningofstomachisprotectedbyoneofthefollowingfromhydrochloric

acid.Choosethecorrectone

(a) Pepsin

(b) Mucus

(c) Salivaryamylase

(d) Bile

Ans.(b)Mucus

Explanation:Mucusprotectstheinnerliningofstomachfromhydrochloricacid.

7. Whichpartofalimentarycanalreceivesbilefromtheliver?

(a) Stomach

(b) Smallintestine

(c) Largeintestine

(d) Oesophagus

Ans.(b)Smallintestine

Explanation:Bilefromgallbladdergoestosmallintestinethroughhepatopancreaticduct.

8. Afewdropsofiodinesolutionwereaddedtoricewater.Thesolutionturnedblue-

blackincolour.Thisindicatesthatricewatercontains

(a) complexproteins

(b) simpleproteins

(c) fats


(d) starch

Ans.(d)Starch

Explanation:Starchmakesadarkbluecomplexwithiodine.Thisisthemostoftenusedtest

tocheckthepresenceofstarchinsomething.

9. Inwhichpartofthealimentarycanalfoodisfinallydigested?

(a) Stomach

(b) Mouthcavity

(c) Largeintestine

(d) Smallintestine

Ans.(d)Smallintestine

Explanation:Partialdigestionoffoodtakesplaceinmouthandstomach.Digestiondoesnot

happeninlargeintestine.Itisthesmallintestine,wheredigestioniscompleted.

10. Choosethefunctionofthepancreaticjuicefromthefollowing

(a) trypsindigestsproteinsandlipasecarbohydrates

(b) trypsindigestsemulsifiedfatsandlipaseproteins

(c) trypsinandlipasedigestfats

(d) trypsindigestsproteinsandlipaseemulsifiedfats

Ans.(d)Trypsindigestsproteinsandlipaseemulsifiedfats

Explanation:Trypsincompletesthedigestionofprotein.Lipasedigestsemulsifiedfatto

convertitintofattyacidsandglycerol.

11. Whenairisblownfrommouthintoatest-tubecontaininglimewater,thelime

waterturnedmilkyduetothepresenceof


(a) oxygen

(b) carbondioxide

(c) nitrogen

(d) watervapour

Ans.(b)Carbondioxide

Explanation: Carbon dioxide reacts with limewater [Ca(OH)2 to form calcium carbonate

whichmakesthelimewatermilky.

12. Thecorrectsequenceofanaerobicreactionsinyeastis

(a)

(b)

(c)

(d)

Ans.(d)

Explanation:Breakdownofpyruvate;underanaerobiccondition;takesplaceincytoplasm

ofyeast.Ethanolandcarbondioxideareproducedattheendofthisreaction.

13. Whichofthefollowingismostappropriateforaerobicrespiration?

(a)

(b)

(c)

(d)


Ans.(d)

Explanation:Inaerobicrespiration,breakdownofpyruvatetakesplaceinmitochondria.

Carbondioxideandwaterareproducedattheendofthisreaction.

14. Whichofthefollowingstatement(s)is(are)trueaboutrespiration?

(i) Duringinhalation,ribsmoveinwardanddiaphragmisraised

(ii) Inthealveoli,exchangeofgasestakesplacei.e.,oxygenfromalveolarairdiffusesinto

bloodandcarbondioxidefrombloodintoalveolarair

(iii) Haemoglobinhasgreateraffinityforcarbondioxidethanoxygen

(iv) Alveoliincreasesurfaceareaforexchangeofgases

(a) (i)and(iv)

(b) (ii)and(iii)

(c) (i)and(iii)

(d) (ii)and(iv)

Ans.(d)(ii)and(iv)

Explanation:Statement(i)isincorrect.Duringinhalation,ribsmoveoutwardand

diaphragmislowered.Statement(iii)isincorrectbecausehaemoglobinhasgreateraffinity

foroxygenthancarbondioxide.

15. Whichisthecorrectsequenceofairpassageduringinhalation?

(a) Nostrils→larynx→pharynx→trachea→lungs

(b) Nasalpassage→trachea→pharynx→larynx→alveoli

(c) larynx→nostrils→pharynx→lungs

(d) Nostrils→pharynx→larynx→trachea→alveoli


Ans.(d)Nostrils→pharynx→larynx→trachea→alveoli

Explanation:Hereisthecorrectsequenceoforgansinhumanrespiratorsystem.

16. Duringrespirationexchangeofgasestakeplacein

(a) tracheaandlarynx

(b) alveolioflungs

(c) alveoliandthroat

(d) throatandlarynx

Ans.(b)Alveolioflungs

Explanation:Tracheaandlarynxjustserveaspassageforair.Exchangeofgasestakesplace

inalveoli;whereoxygendiffusesintobloodandcarbondioxidecomesoutofblood.

17. Whichofthefollowingstatement(s)is(are)trueaboutheart?

(i) Leftatriumreceivesoxygenatedbloodfromdifferentpartsofbodywhileright

atriumreceivesdeoxygenatedbloodfromlungs

(ii) Leftventriclepumpsoxygenatedbloodtodifferentbodypartswhilerightventricle

pumpsdeoxygenatedbloodtolungs

(iii) Leftatriumtransfersoxygenatedbloodtorightventriclewhichsendsitto


differentbodyparts

(iv) Rightatriumreceivesdeoxygenatedbloodfromdifferentpartsofthebodywhile

leftventriclepumpsoxygenatedbloodtodifferentpartsofthebody

(a) (i)

(b) (ii)

(c) (ii)and(iv)

(d) (i)and(iii)

Ans.(c)(ii)and(iv)

Explanation:Deoxygenatedbloodcirculatesthroughrightpartoftheheart,while

oxygenatedbloodcirculatesthroughleftpartoftheheart.Atriumreceivesblood,while

ventriclepumpsthebloodout.

18. Whatpreventsbackflowofbloodinsidetheheartduringcontraction?

(a) Valvesinheart

(b) Thickmuscularwallsofventricles

(c) Thinwallsofatria

(d) Alloftheabove

Ans.(a)Valvesinheart

Explanation:Wallsofheartfacilitatethepumpingactiononlyandhavenorolein

preventingbackflowofblood.

19. Singlecirculationi.e.,bloodflowsthroughtheheartonlyonceduringonecycleof

passagethroughthebody,isexhibitedby

(a) Labeo,Chameleon,Salamander


(b) Hippocampus,Exocoetus,Anabas

(c) Hyla,Rana,Draco

(d) Whale,Dolphin,Turtle

Ans.(b)Hippocampus,Exocoetus,Anabas

Explanation:Inoption‘a’;salamanderisamphibian,whilechameleonisreptile;andthey

havethreechamberedheart.Thus,theseanimalsshowpartialdoublecirculation.Inoption

‘c’allanimalsareamphibians.

Inoption‘d’whaleismammal,whileturtleisreptile.Mammalshavefour-chamberedheart

andcompletelydoublecirculation.

20. Inwhichofthefollowingvertebrategroup/groups,heartdoesnotpumpoxygenated

bloodtodifferentpartsofthebody?

(a) Piscesandamphibians

(b) Amphibiansandreptiles

(c) Amphibiansonly

(d) Piscesonly

Ans.(d)Piscesonly

Explanation:Thishappensbecauseofsinglecirculation.Thedeoxygenatedbloodfromall

bodypartscomestoheartandispumpedtothegillswhereitgetsoxygenated.This

oxygenatedbloodistransferredtoallbodypartsfromgills.

21. Choosethecorrectstatementthatdescribesarteries.

(a) Theyhavethickelasticwalls,bloodflowsunderhighpressure;collectbloodfrom

differentorgansandbringitbacktotheheart

(b) Theyhavethinwallswithvalvesinside,bloodflowsunderlowpressureandcarryblood


awayfromthehearttovariousorgansofthebody

(c) Theyhavethickelasticwalls,bloodflowsunderlowpressure;carrybloodfromtheheart

tovariousorgansofthebody

(d) Theyhavethickelasticwallswithoutvalvesinside,bloodflowsunderhighpressureand

carrybloodawayfromthehearttodifferentpartsofthebody.

Ans.(d)Theyhavethickelasticwallswithoutvalvesinside,bloodflowsunderhighpressure

andcarrybloodawayfromthehearttodifferentpartsofthebody.

22. Thefiltrationunitsofkidneysarecalled

(a) Ureter

(b) Urethra

(c) Neurons

(d) Nephrons

Ans.(d)Nephrons

Explanation:Duetothis,nephroniscalledthefunctionalunitofKidney.

23. Oxygenliberatedduringphotosynthesiscomesfrom

(a) water

(b) chlorophyll

(c) carbondioxide

(d) glucose

Ans.(a)water

Explanation:Splittingofwatermolecule,resultsinliberationofoxygenandhydrogen.

Hydrogenisutilizedforreductionofcarbondioxidesothatcarbohydratecanbemade.


24. Thebloodleavingthetissuesbecomesricherin

(a) carbondioxide

(b) water

(c) heamoglobin

(d) oxygen

Ans.(a)carbondioxide

Explanation:Carbondioxideaccumulatesintissuesbecauseofrespirationincells.Thus,

bloodleavingthetissuesbecomesricherincarbondioxide.

25. Whichofthefollowingisanincorrectstatement?

(a) Organismsgrowwithtime

(b) Organismsmustrepairandmaintaintheirstructure

(c) Movementofmoleculesdoesnottakeplaceamongcells

(d) Energyisessentialforlifeprocesses

Ans.(c)Movementofmoleculesdoesnotakeplaceamongcells

Explanation:Movementofmoleculesisanimportantaspectoflifeprocessanditis

necessarythatsuchmovementstakeplaceamongcells.

26. Theinternal(cellular)energyreserveinautotrophsis

(a) glycogen

(b) protein

(c) starch

(d) fattyacid


Ans.(c)Starch

Explanation:Plantsstorefoodintheformofstarch.

27. Whichofthefollowingequationsisthesummaryofphotosynthesis?

(a)

(b)

(c)

(d)

Ans.(c)

Explanation:Option‘a’showscorrectreaction.Butoption‘c’showscorrectreactionaswell

asotherimportantfactorsofreaction.Option‘b’isnotabalancedequation.Option‘d’shows

carbondioxideamongtheproducts;whichiswrong.

28. Choosetheeventthatdoesnotoccurinphotosynthesis

(a) Absorptionoflightenergybychlorophyll

(b) Reductionofcarbondioxidetocarbohydrates

(c) Oxidationofcarbontocarbondioxide

(d) Conversionoflightenergytochemicalenergy

Ans.(c)Oxidationofcarbontocarbondioxide

29. Theopeningandclosingofthestomatalporedependsupon

(a) oxygen

(b) temperature


(c) wateringuardcells

(d) concentrationofCO2instomata

Ans.(c)Wateringuardcells

Explanation:Whenwaterenterstheguardcells.theybecometurgidandfacilitatethe

openingofguardcells.Whenwatercomesoutofguardcells,theybecomeflaccidand

facilitatetheclosingofguardcells.

30. Choosetheformsinwhichmostplantsabsorbnitrogen

(i) Proteins

(ii) NitratesandNitrites

(iii) Urea

(iv) Atmosphericnitrogen

(a) (i)and(ii)

(b) (ii)and(iii)

(c) (iii)and(iv)

(d) (i)and(iv)

Ans.(b)(ii)and(iii)

Explanation:Plantscannottakeupatmosphericnitrogenandhenceoption‘iv’isincorrect.

Proteinissynthesizedbyplantsandhenceoption‘i’isincorrect.

31. Whichisthefirstenzymetomixwithfoodinthedigestivetract?

(a) Pepsin

(b) Cellulase

(c) Amylase


(d) Trypsin

Ans.(c)Amylase

Explanation:Amylaseispresentinsaliva;whichissecretedinmouth.Hence,thisisthefirst

enzymetomixwithfood.

32. Whichofthefollowingstatement(s)is(are)correct?

(i) Pyruvatecanbeconvertedintoethanolandcarbondioxidebyyeast

(ii) Fermentationtakesplaceinaerobicbacteria

(iii) Fermentationtakesplaceinmitochondria

(iv) Fermentationisaformofanaerobicrespiration

(a) (i)and(iii)

(b) (ii)and(iv)

(c) (i)and(iv)

(d) (ii)and(iii)

Ans.(c)(i)and(iv)

Explanation:Fermentationtakesplaceinanaerobes.Fermentationdoesnottakeplacein

mitochondria.Hence,Options(ii)and(iii)areincorrect.

33. Lackofoxygeninmusclesoftenleadstocrampsamongcricketers.Thisresultsdue

to

(a) conversionofpyruvatetoethanol

(b) conversionofpyruvatetoglucose

(c) non-conversionofglucosetopyruvate


(d) conversionofpyruvatetolacticacid

Ans.(d)conversionofpyruvatetolacticacid

Explanation:Incaseofexcessdemandofenergyinmuscles,anaerobicrespirationtakes

placeinmusclecells.Thisresultsinaccumulationoflacticacidinmuscleswhichresultsin

cramps.

34. Choosethecorrectpathofurineinourbody

(a) kidney→ureter→urethra→urinarybladder

(b) kidney→urinarybladder→urethra→ureter

(c) kidney→ureters→urinarybladder→urethra

(d) urinarybladder→kidney→ureter→urethra

Ans.(c)kidney→ureters→urinarybladder→urethra

Explanation:Refertofig:6.13(NCERTTextbook)forpropersequenceoforgansinexcretory

system.

35. Duringdeficiencyofoxygenintissuesofhumanbeings,pyruvicacidisconverted

intolacticacidinthe

(a) cytoplasm

(b) chloroplast

(c) mitochondria

(d) golgibody

Ans.(a)cytoplasm

Explanation:Anaerobicrespirationtakesplaceincytoplasm.



Short Answer Questions

36. Namethefollowing

(a) Theprocessinplantsthatlinkslightenergywithchemicalenergy

Ans.Photosynthesis

(b) Organismsthatcanpreparetheirownfood

Ans.Autotrophs

(c) Thecellorganellewherephotosynthesisoccurs

Ans.Chloroplast

(d) Cellsthatsurroundastomatalpore

Ans.Guardcells

(e) Organismsthatcannotpreparetheirownfood

Ans.Heterotrophs

(f) Anenzymesecretedfromgastricglandsinstomachthatactsonproteins.

Ans.Pepsin

37. “Allplantsgiveoutoxygenduringdayandcarbondioxideduringnight”.Doyou

agreewiththisstatement?Givereason.

Ans.Thisisanincorrectstatement.Allplantscarryonrespirationthroughout24hoursand

thusgiveoutcarbondioxidethroughoutthe24hours.Butphotosynthesishappensonlyin


presenceofsunlightandoxygenisreleasedduringdaytime.

38. Howdotheguardcellsregulateopeningandclosingofstomatalpores?

Ans.Whenwaterenterstheguardcells,theybecometurgid.Thisresultsinopeningof

stomatalpore.Whenwaterexitsfromtheguardcells,theybecomeflaccid.Thisresultsin

closingofstomata.

39. Twogreenplantsarekeptseparatelyinoxygenfreecontainers,oneinthedarkand

theotherincontinuouslight.Whichonewilllivelonger?Givereasons.

Ans.Theplantwhichiskeptincontinuouslightlivelonger.Weknowthatplantrelease

carbondioxideduringrespiration.Incaseofplantwhichisbeingkeptindark,carbon

dioxidewillaccumulateinthecontainer.Thiswillfinallyresultinlackofoxygenforthe

plantandplantwoulddie.Incaseofplantwhichisbeingkeptinlight,carbondioxideshall

beutilizedduringphotosynthesis.Thiswillhelpinmaintainingtheavailabilityofoxygenfor

respiration.Asaresult,thisplantwilllivelonger.

40. Ifaplantisreleasingcarbondioxideandtakinginoxygenduringtheday,doesit

meanthatthereisnophotosynthesisoccurring?Justifyyouranswer.

Ans.Ifplantisreleasingcarbondioxideandtakinginoxygenduringtheday,itmeansthat

respirationishappeninginplant.Butitdoesnotmeanthatphotosynthesisisnothappening.

Carbondioxidereleasedafterrespirationcomesoutofstomata.Respirationisindependent

ofphotosynthesis.

41. Whydofishesdiewhentakenoutofwater?

Ans.Fishcanonlyconsumeoxygeninthedissolvedformpresentinwater.Also,thegillsof

fishescannotconverttheoxygenpresentinair,theyareadaptedtodissolvedoxygen.

42. Differentiatebetweenanautotrophandaheterotroph.

Ans.


43. Is‘nutrition’anecessityforanorganism?Discuss.

Ans.Nutritionisrequiredbyeveryorganismforvariouspurposes.Anorganismneeds

energytocarryoutvariousmetabolicactivities,andthisenergycomesfromnutrients

presentinfood,whichisthemostpotentialsourceofnutrition.

44. Whatwouldhappenifgreenplantsdisappearfromearth?

Ans.Greenplantsarethemainconductsthroughwhichsolarenergyistrappedand

channeledtoallotherorganisms.Greenplantsarethemainsourceoffood(directlyor

indirectly)formostoftheheterotrophs.Greenplantsmaintainthebalanceintheecosystem.

Thusdisappearanceofplantsfromearthwillleadtocatastrophicconsequenceslike

increasedatmospherictemperature,deathofvariousheterotrophswhichmayimbalancethe

ecosytem.

45. Leavesofahealthypottedplantwerecoatedwithvaseline.Willthisplantremain

healthyforlong?Givereasonsforyouranswer.

Ans.IfleavesofahealthypottedplantarecoatedwithVaseline,itwillclogthestomatal

poresonleaves.Blockageofstomatawillstoptranspirationandexchangeofgasesfrom

leaves.Transpirationplaysanimportantroleinascentofsapinplants.Hence,lackof

transpirationwillstopascentofsap.Moreover,stoppageofexchangeofgaseswouldalso

stoprespirationandphotosynthesisinleaves.Thiswillresultindeathofleavesandfinally

theplantwoulddieduetolackoffood.

46. Howdoesaerobicrespirationdifferfromanaerobicrespiration?

Ans.


47. MatchthewordsofColumn(A)withthatofColumn(B)

Ans.(a)-(ii),

(b)-(i),

(c)-(iv),

(d)-(iii)

48. Differentiatebetweenanarteryandavein.

Ans.

49. Whataretheadaptationsofleafforphotosynthesis?

Ans.Leavesshowfollowingadaptationsforphotosynthesis:


(a) Flatsurfacetoallowgreaterexposuretosunlight

(b) Presenceofchlorophylltotrapsolarenergy

(c) Largernumberofstomataonlowersurfaceforeasytranspiration.

50. Whyissmallintestineinherbivoreslongerthanincarnivores?

Ans.Thefoodofherbivorescontainsahugeamountofcellulose.Theanimalsneedthe

assistanceofcertainbacteriatodigestcelluloseandthisprocesstakestime.Duetothis,

herbivoreshavelongersmallintestinethancarnivores.Meatiseasiertodigestandhence

carnivoreshavesmallintestinewhichismuchsmallerthaninherbivores.

51. Whatwillhappenifmucusisnotsecretedbythegastricglands?

Ans.Mucusplaysimportantroleindigestivesystem.Mucuspreventstheinnerliningof

digestivesystemfrombecomingdry.Thishelpsineasiermovementoffoodthroughthe

digestivesystem.Moreover,mucusinstomachprotectstheinnerliningfromdamageby

hydrochloricacid.So,lackofmucuswillresultindamagetotheinnerliningofstomach.It

mayresultingastriculcers.

52. Whatisthesignificanceofemulsificationoffats?

Ans.Fatispresentintheformoflargeglobules.Fortheconcernedenzyme,itisdifficultto

digestlargeglobulesoffat.Emulsificationoffatresultsinfatbreakingintosmallerglobules.

Afterthat,itbecomeseasierfortheenzymetodigestfat.

53. Whatcausesmovementoffoodinsidethealimentarycanal?

Ans.Foodmovesinsidethealimentarycanalbecauseofperistalsis.Alimentarycanalhas

muscularwalls.Duetothis,thealimentarycanalcontractsandrelaxesinalternative

fashion.

54. Whydoesabsorptionofdigestedfoodoccurmainlyinthesmallintestine?


Ans.Smallintestinehasspecializedstructurestofacilitateabsorption.Theinnerliningof

smallintestinehasnumerousfolds;toincreasetheareaofabsorption.Thefinger-like

projectionsinsidethesmallintestinearerichlysuppliedbybloodvessels.Thisalsohelpsin

absorptionoffood.Duetothis,absorptionofdigestedfoodoccursmainlyinthesmall

intestine.

55. MatchGroup(A)withGroup(B)

Ans.(a)-iv

(b)-iii

(c)-i

(d)-ii

56. Whyistherateofbreathinginaquaticorganismsmuchfasterthaninterrestrial

organisms?

Ans.Theavailabilityofoxygenismuchlessinaquaticenvironmentthaninterrestrial

environment.Duetothis,aquaticorganismsneedtoworkhardertoobtainoxygen.Hence,

rateofbreathinginaquaticorganismsismuchfasterthaninterrestrialorganisms.

57. Whyisbloodcirculationinhumanheartcalleddoublecirculation?

Ans.Inhumanheart,bloodpassesthroughthehearttwiceduringonecardiaccycle.The

deoxygenatedbloodcomestotheheartandgoestothelungsforoxygenation.

Simultaneously,theoxygenatedbloodcomestotheheartfromlungsandgoestodifferent

organs.Duetothis,bloodcirculationinhumanheartiscalleddoublecirculation.


58. Whatistheadvantageofhavingfourchamberedheart?

Ans.Four-chamberedheartgivesfollowingadvantages:

(a) Thereisclearcutdivisionoflabouramongdifferentchambers.Atriareceivebloodand

ventriclespumptheblood.

(b) Thereiscompletesegregationofoxygenatedanddeoxygenatedbloodintheheart.

(c) Heart’sefficiencyismoreinthisdesign.

59. Mentionthemajoreventsduringphotosynthesis.

Ans.Followingarethemajoreventsduringphotosynthesis:


(b) Conversionoflightenergyintochemicalenergy.

(c) Splittingofwatermoleculesintohydrogenandoxygen.

(d) Reductionofcarbondioxidetoformcarbohydrate.

60. Ineachofthefollowingsituationswhathappenstotherateofphotosynthesis?

(a) Cloudydays

Ans.Availabilityofsunlightislessoncloudydays.Thiswillreducetherateof

photosynthesis.


(b) Norainfallinthearea

Ans.Noeffect

(c) Goodmanuringinthearea

Ans.Noeffect

(d) Stomatagetblockedduetodust

Ans.Openingofstomataisessentialforavailabilityofcarbondioxideforphotosynthesis.

Blockageofstomatawillreducetherateofphotosynthesis.

61. Nametheenergycurrencyinthelivingorganisms.Whenandwhereisitproduced?

Ans.AdenosineTriphosphate(ATP)iscalledtheenergycurrencyinlivingorganisms.Itis

producedinmitochondriaduringrespiration.

62. Whatiscommonforcuscuta,ticksandleeches?

Ans.Allofthemareparasites.Theyliveonorinsidethebodyofanotherorganismtoget

food.Theyalwaysharmtheirhosts.

63. Explaintheroleofmouthindigestionoffood.

Ans.Roleofmouthindigestionoffood:

(a) Ingestionoffoodhappensthroughmouth.

(b) Masticationoffoodbreaksthefoodintosmallerparticles.

(c) Salivamakesthefoodslipperysothatitbecomeseasytoswallowthefood.

(d) Salivaryamylaseconvertsstarchintosugar.

64. Whatarethefunctionsofgastricglandspresentinthewallofthestomach?

Ans.Gastricglandssecretehydrochloricacid,pepsinandmucus.Theyhavefollowing


functions:

(a) Hydrochloricacidkillsanygermwhichmaybepresentinfood.Itmakestheenvironment

inthestomachacidic;whichisessentialforfunctioningofgastricenzyme.

(b) Pepsindigestsprotein.

(c) Mucuspreventstheinnerliningofstomachfromgettingdamagedbyhydrochloricacid.

65. MatchthetermsinColumn(A)withthoseinColumn(B)

Ans.(a)-i(b)-iv(c)-ii(d)-iii

66. Namethecorrectsubstratesforthefollowingenzymes

(a) Trypsin(b)Amylase (c) Pepsin(d)Lipase

Ans.(a)Protein(b)Starch (c) Protein(d)Fat

67. Whydoveinshavethinwallsascomparedtoarteries?

Ans.Bloodflowthroughveindoesnotexertpressureonthewallsofveins.Duetothis,they

donotneedthickwalls.Hence,veinshavethinwallsascomparedtoarteries.

68. Whatwillhappenifplateletswereabsentintheblood?

Ans.Plateletsplayanimportantroleinclottingofblood.Clottingofbloodisdefense

mechanism.Itpreventsexcesslossofbloodincaseofinjury.Lackofplateletwillnotallow

thebloodtoclot.Thiswillresultinexcesslossofbloodincaseofinjury.Thismayprovefatal

fortheperson.


69. Plantshavelowenergyneedsascomparedtoanimals.Explain.

Ans.Plantsremainfixedataplacebecausetheydonotneedtomoveinsearchoffood.Asa

result,plantsdonotneedtohavelocomotion,thewayanimalsdo.Moreover,mostofthe

movementsofsubstancesinplantshappenthroughpassivetransport;whichdoesnotneed

energy.Duetothis,theenergyrequirementinplantsislowascomparedtoanimals.

70. Whyandhowdoeswaterentercontinuouslyintotherootxylem?

Ans.Roothairshavethinwalls.Duetothis,waterenterstheroothairsbecauseofosmosis.

Waterfromroothairscontinuouslymovesintotherootxylem.Tomaintaintheosmotic

gradients,thecellsofroothairstakeupionsfromthesoil.

71. Whyistranspirationimportantforplants?

Ans.Significanceoftranspiration:

(a) Itcreatestranspirationpulltofacilitateascentofsap.

(b) Ascentofsapisnecessarytomakewateravailableforphotosynthesis.

(c) Ithelpsaplanttogetridofexcesswater.

72. Howdoleavesofplantshelpinexcretion?

Ans.Leavesplayimportantroleinexcretioninplants.Mostofthecarbondioxideexits

throughstomatainleaves.Manyexcretoryproductsaccumulateinleaves.Plantsshedleaves

togetridexcretoryproducts.


Long Answer Questions

73.ExplaintheprocessofnutritioninAmoeba.

Ans.Amoebashowsholozoicnutritionwhichiscomprisedoffollowingsteps:

Ingestion,Digestion,Absorption,AssimilationandEgestion

Ingestion:Amoebamakesfinger-likeprojectionsoutsideitsbody.Theseprojectionsare

calledpseudopodia.Amoebatrapsfoodparticlewithpseudopodia.Afterthat,amoebatakes

inthefoodparticle;alongwithwater.

Digestion:Amoebamakesfoodvacuoleafteringestingthefoodparticle.Enzymesare

releasedinthefoodvacuolefordigestion.

Absorption:Afterdigestion,nutrientsenterthecytoplasmthroughosmosis.

Assimilation:Nutrientsareutilizedbythecellforvariouspurposes.

Egestion:Foodvacuolegoesnearthecellmembranetoemptyitscontentsoutsidethecell.

Thisresultsinexpulsionofwastematerialsfromthecell.

74. Describethealimentarycanalofman.


Ans.Thehumanalimentarycanalhasfollowingparts:

BuccalCavity:Buccalcavitycontainstongue,teethandsalivaryglands.Foodentersthe

digestivesystemthroughbuccalcavity.

Oesophagus:Buccalcavityisconnectedtoalongtube-likestructure;calledoesophagus.

Oesophagushasavalvetopreventthebackflowoffoodintomouth.

Stomach:StomachisaJ-shapedorgan.Thebuccalcavityopensintothestomach.Wallsof

stomacharecomposedofmuscles.Gastricglandsarepresentinthestomach.Theseglands

secretehydrochloricacid,pepsinandmucus.

SmallIntestine:Thisislongandhighlycoiledstructure.Thelumenofthesmallintestineis

smallerthanthatoflargeintestine.Thestomachopensintosmallintestine.The

hepatopancreaticductopensintothesmallintestine.Villiarepresentinsmallintestineto

facilitateabsorptionoffood.

LargeIntestine:Thisisshorterthansmallintestine.Thelumenoflargeintestineislarger

thanthatofsmallintestine.

Rectum:Largeintestineopensintorectum.Wastematerialsandundigestedfoodarestored

inrectum.

75. Explaintheprocessofbreathinginman.

Ans.Breathinginvolvestwostep,viz.inhalationandexhalation.


Inhalation:Theprocessoftakinginaircalledinhalation.Duringthisprocess,ribscomeout

anddiaphragmmovesdown.Thisincreasesthevolumeinsidethelungsandreducesthe

pressureinlungs.Asaresult,airmovestowardsthelungs.

Exhalation:Theprocessofgivingoutairiscalledexhalation.Duringthisprocess,ribsgoin

anddiaphragmmovesup.Thisreducesthevolumeinsidethelungsandincreasesthe

pressureinlungs.Asaresult,airmovesoutofthelungs.

76. Explaintheimportanceofsoilforplantgrowth.

Ans.Importanceofsoilforplantgrowth:

(a) Soilprovidesthebaseonwhichaplantcangrow.

(b) Soilservesasreservoirofwaterforplants.

(c) Soilservesasreservoirofdifferentmineralswhichareessentialforgrowthofplants.

(d) Soilcontainsmanyorganicmaterialswhichprovidenutrientstoplants.

77. Drawthediagramofalimentarycanalofmanandlabelthefollowingparts.Mouth,

Oesophagus,Stomach,Intestine

Ans.


78. Howdocarbohydrates,proteinsandfatsgetdigestedinhumanbeings?

Ans.Digestionofcarbohydrates:Digestionofcarbohydratesbeginsfrombuccalcavity.

Salivaryamylaseconvertsstarchintosugar.Othercomplexcarbohydratesareconverted

intoglucoseinthesmallintestine.

DigestionofProteins:Proteinispartiallydigestedinthestomach.Forthis,stomachsecretes

theenzymepepsin.Insmallintestine,pancreaticjuiceprovidestheenzymestrypsinand

chymotrypsin.Theseenzymescompletethedigestionofproteins.

DigestionofFats:Digestionoffatstakesplaceinsmallintestine.Bile;fromliver;emulsifies

thefat.Duetothis,fatisbrokenintosmallglobules.Thismakesiteasierfortheenzymeto

digestfat.Lipaseistheenzymewhichconvertsfatintoglycerolandfattyacid.

79. Explainthemechanismofphotosynthesis.

Ans.Photosynthesisistheprocessbywhichgreenplantspreparetheirfoodinthepresence

ofsunlight.Greenplantsutilizecarbondioxideandwatertomakecarbohydrate.The

reactionofphotosynthesiscanbeshownbyfollowingequation:

ThewholeprocessofPhotosynthesisiscomposedoffollowingsteps:


(b) Conversionoflightenergyintochemicalenergy

(c) splittingofwatermoleculesintohydrogenandoxygen.


(d) Reductionofcarbondioxidetoformcarbohydrate

Thesestepsneednottakeplaceoneafteranotherimmediately.Forexample;desertplants

takeupcarbondioxideatnighttomakeanintermediate.Duringdaytime,theymake

carbohydrate.Afterphotosynthesis,carbohydrateisconvertedintostarchandstarchis

storedindifferentplantorgans.

80. Explainthethreepathwaysofbreakdowninlivingorganisms.

Ans.Thebreakdownofsugarcanbeshownbyfollowingdiagram:

Inallorganisms,glucoseisfirstconvertedintopyruvate.Glucoseisa6-carbonmolecule,

whilepyruvateisa3-carbonmolecule.Thisstepissameinallorganismsandithappensin

cytoplasm.Furtherbreakdownofpyruvatecanhappeninanyofthefollowingways:

InYeast:Inyeast,breakdownofpyruvatetakeplaceinabsenceofoxygen.Duetothis,itis

calledanaerobicrespiration.Pyruvateisbrokendownintoethanolandcarbondioxide.

Inmusclecells:Duringstrenuousphysicalactivity,theenergydemandfrommusclecells

suddenlyincreases.Thisiscompensatedbyanaerobicrespirationinmusclecells.Insucha

situation,pyruvateisbrokendownintolacticacid.

Inmitochondria:Inthiscase,breakdownofpyruvatetakesplaceinpresenceofoxygen.

Duetothis,itiscalledaerobicrespiration.Pyruvateisbrokendownintocarbondioxideand

water.Aerobicrespirationisthenormismostofthelivingbeings.

81. Describetheflowofbloodthroughtheheartofhumanbeings.


Ans.Bloodflowthroughthehumanhearttakesplaceinfollowingsteps:

Deoxygenatedbloodfromdifferentorganscomestotherightatriumthroughthe

venacava.

Fromtherightatrium,bloodgoestotherightventricle.Thetricuspidvalvebetween

therightatriumandrightventriclepreventsthebackflowofblood.

Fromtherightventricle,bloodgoestothelungsthroughpulmonaryartery.Inside

thelungs,carbondioxideisremovedfromthebloodandoxygenenterstheblood.

Fromthelungs,bloodgoestotheleftatriumthroughpulmonaryvein.

Fromtheleftatrium,bloodgoestotheleftventricle.

Fromtheleftventricle,bloodispumpedintotheaortasothatitcanbesuppliedto

differentorgans.

82. Describetheprocessofurineformationinkidneys.

Ans.Thefunctionalunitofkidneyiscallednephron.


Anephroniscomposedofatuftofbloodcapillariesandhighlycoiledducts.Thetuft

ofbloodcapillariesissurroundedbyacup-shapedstructure;calledBowman’s

capsule.

Wastematerialfrombloodarefilteredoutofthecapillariesandtheygothroughthe

wallofBowman’scapsule.

Afterthat,thewastematerialandwaterpassthroughtheducts.Whenthemixtureof

waterandothermaterialsmovethroughtheduct,somematerialsandwaterare

reabsorbed.Thisdependsonexcessamountofwaterpresentinthebody.

Afterreabsorptionofwaterandothermaterial,urinebecomesconcentrated.This

thengoestothecollectingduct.

Urinefromcollectingductsmovesthroughureterintotheurinarybladder.Fromthe

urinarybladder,urineisexpelledfromthebodyasandwhenrequired.


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Exercise Multiple Choice Questions (MCQs)...Chapter 6 Life Processes Multiple Choice Questions (MCQs) 1.Which of the following statements about the autotrophs is incorrect? (a)They