CBSE NCERT Solutions for Class 11 biology Chapter 4 Exercises Q.1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account? Solution: The purpose of the classification of animals is to trace the common features among different species and group them on the basis of common fundamental features rather than considering every feature of an organism. If every individual will have to be studied independently, the correlation among species cannot be identified and hence, evolutionary significance at an individual level cannot be traced. The interrelationship among different animals will not be traceable. If only common features of organisms are taken into account it will lead to a grouping of unrelated organisms. For example the birds, bats and butterflies all have wings but basically have different origin and characteristics. Similarly, the whale seems to belong to class Pisces but is actually a mammal and bats look like birds but are mammals. Thus, for grouping the organisms their evolutionary characters must be taken into consideration. Q.2. How important is the presence of an air bladder in Pisces? Solution: Air bladder in bony fishes (Class– Osteichthyes), allows them to balance themselves in water without sinking, hence, maintaining the buoyancy. It also allows the fish to move upwards, downwards or stay still in the water current enabling them to survive in an aquatic medium without wasting extra energy. Q.3. What are the modifications that are observed in birds that help them fly? Solution: The birds have the following features which allow them to fly: The forelimbs are modified into wings that enable the birds to fly and the hindlimbs are modified to swim, walk or perch on branches. They have bony endoskeleton and long hollow bones with air cavities (pneumatic bones), thus, reducing the bodyweight of birds. They have streamlined shaped body, which allows smooth and rapid movement in the air. Their body is covered with feathers, hence, provide insulation to the body. Air sacs present along with lungs aid in respiration. Q.4. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why? Solution: Oviparous animals are those animals that lay eggs and young ones hatch from them. The eggs develop outside the parent and are susceptible to predators attack. Hence, the chances of survival of all the embryos are not possible. So the oviparous mother lays many eggs in order to compensate for any loss and there is less burden for the mother to carry the progeny. Viviparous animals are those animals that give birth to the young ones and the mother produces less young ones. The embryo develops within the body of the viviparous mother in the safe conditions and environment with the least exposure to external conditions and predators until birth. Only a few young ones can be properly incubated due to viviparity. Hence, the number of young ones produced by an oviparous and viviparous mother are not equal. Q.5. Segmentation in the body is first observed in which of the following. PlatyhelminthesAschelminthesAnnelida Solution: The body of Annelids organisms is marked by the presence of true body segments or metameres, hence the name Annelida. These are the first organisms in which true metamerism is found. Arthropoda NCERT Biology Grade 11 Chapter 4 Animal kingdom Practice more on Animal kingdom Page 1 www.embibe.com
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CBSENCERTSolutionsforClass11biologyChapter4
Exercises
Q.1. Whatarethedifficultiesthatyouwouldfaceinclassificationofanimals,ifcommonfundamentalfeaturesarenottakenintoaccount?
Solution: Thepurposeoftheclassificationofanimalsistotracethecommonfeaturesamongdifferentspeciesandgroupthemonthebasisofcommonfundamentalfeaturesratherthanconsideringeveryfeatureofanorganism.
Ifeveryindividualwillhavetobestudiedindependently,thecorrelationamongspeciescannotbeidentifiedandhence,evolutionarysignificanceatanindividuallevelcannotbetraced.Theinterrelationshipamongdifferentanimalswillnotbetraceable.
Ifonlycommonfeaturesoforganismsaretakenintoaccountitwillleadtoagroupingofunrelatedorganisms.Forexamplethebirds,batsandbutterfliesallhavewingsbutbasicallyhavedifferentoriginandcharacteristics.Similarly,thewhaleseemstobelongtoclassPiscesbutisactuallyamammalandbatslooklikebirdsbutaremammals.Thus,forgroupingtheorganismstheirevolutionarycharactersmustbetakenintoconsideration.
Q.2. HowimportantisthepresenceofanairbladderinPisces?
Solution: Airbladderinbonyfishes(Class–Osteichthyes),allowsthemtobalancethemselvesinwaterwithoutsinking,hence,maintainingthebuoyancy.Italsoallowsthefishtomoveupwards,downwardsorstaystillinthewatercurrentenablingthemtosurviveinanaquaticmediumwithoutwastingextraenergy.
Q.3. Whatarethemodificationsthatareobservedinbirdsthathelpthemfly?
Solution: Thebirdshavethefollowingfeatureswhichallowthemtofly:
Theforelimbsaremodifiedintowingsthatenablethebirdstoflyandthehindlimbsaremodifiedtoswim,walkorperchonbranches.Theyhavebonyendoskeletonandlonghollowboneswithaircavities(pneumaticbones),thus,reducingthebodyweightofbirds.
Theyhavestreamlinedshapedbody,whichallowssmoothandrapidmovementintheair.Theirbodyiscoveredwithfeathers,hence,provideinsulationtothebody.Airsacspresentalongwithlungsaidinrespiration.
Q.4. Couldthenumberofeggsoryoungonesproducedbyanoviparousandviviparousmotherbeequal?Why?
Solution: Oviparousanimalsarethoseanimalsthatlayeggsandyoungoneshatchfromthem.Theeggsdevelopoutsidetheparentandaresusceptibletopredatorsattack.Hence,thechancesofsurvivalofalltheembryosarenotpossible.Sotheoviparousmotherlaysmanyeggsinordertocompensateforanylossandthereislessburdenforthemothertocarrytheprogeny.
Viviparousanimalsarethoseanimalsthatgivebirthtotheyoungonesandthemotherproduceslessyoungones.Theembryodevelopswithinthebodyoftheviviparousmotherinthesafeconditionsandenvironmentwiththeleastexposuretoexternalconditionsandpredatorsuntilbirth.Onlyafewyoungonescanbeproperlyincubatedduetoviviparity.Hence,thenumberofyoungonesproducedbyanoviparousandviviparousmotherarenotequal.
Q.5. Segmentationinthebodyisfirstobservedinwhichofthefollowing.PlatyhelminthesAschelminthesAnnelida
Solution: ThebodyofAnnelidsorganismsismarkedbythepresenceoftruebodysegmentsormetameres,hencethenameAnnelida.Thesearethefirstorganismsinwhichtruemetamerismisfound.
Arthropoda
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Q.6. Matchthefollowing:
(a)Operculum (i)Ctenophora(b)Parapodia (ii)Mollusca(c)Scales (iii)Porifera(d)CombPlates (iv)Reptilia(e)Radula (v)Annelida(f)Hair (vi)Cyclostomataandchondrictyes.(g)Choanocytes (vii)Mammalia(h)Gillslits (viii)Osteichthyes
Solution: (a)-(viii),
OperculumcoversthegillslitsinOsteichthyes.
(b)-(v),
ParapodiaisthelocomotoryorganellesinthepolypodagroupofphylumAnnelida.
(c)-(iv),
Reptilesaremostlyterrestrialanimalsandtheirbodyiscoveredbydryandcornifiedskin,epidermalscales,orscutes.
(d)-(i),
ThepresenceofcombplatesisacharacteristicfeatureofthephylumCtenophora.
(e)-(ii),
Theradulaisateeth-likestructureusedtocrushthefoodmaterial,presentintheorganismsofphylumMollusca.
(f)-(vii),
Thepresenceofhairinthebodyisanidentifyingfeatureofmammals.
(g)-(iii),
Choanocytes,alsocalledthecollarcellsarepresentinPoriferansandactasadefensesystem.
(h)-(vi),
UncoveredgillslitsarepresentintheCyclostomataandChondrichthyes,whiletheyarecoveredbyoperculumintheOsteichthyes.
(a) Operculum (viii) Osteichthyes(b) Parapodia (v) Annelida(c) Scales (iv) Reptiles(d) CombPlates (i) Ctenophora(e) Radula (ii) Mollusca(f) Hair (vii) Mammalia(g) Choanocytes (iii) Porifera(h) Gillslits (vi) CyclostomataandChondrichthyes.
Q.7. Listoutthenamesofsomeanimalsthatarefoundparasiticonhumanbeings.
Solution: TheanimalsofphylumPlatyhelminthsandAschelminthesthatincludestheflatwormsandroundworms,respectivelyarefoundmostlyinhabitingthedigestivetractbutcanbepresentinotherbodyparts.
Someanimalsthatarefoundparasiticonhumanbeingsare:
1.Fasciolahepatica(LiverFluke)
2.Taeniasolium(Flatworm)3.Ascarislumbricoides(Roundworm)4.Wuchereriaduodenale(Filarialworm)5.Echinococcusgranulosus(HydatidWorm)6.Ancylostomaduedonale(HookWorm)
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Q.8. Ifyouaregivenaspecimen,whatarethestepsthatyouwouldfollowtoclassifyit?
Solution: Aspecimencanbeclassifiedbasedonthefollowingcharacteristics:Theleveloforganisation–Wecancheckwhichoneofthefollowingleveloforganisationthespecimenexhibits.
ThecellularleveloforganisationTissueleveloforganisationOrganleveloforganisation.
Structuralsymmetryoftheanimalbody.
SymmetricAsymmetric
Numberofembryoniclayers–Theanimalcanhavetwoorthreegermlayersonthebasisofwhichitcanbeclassifiedinto-
DiploblasticTriploblastic
Onthebasisofpresenceorabsenceofcoelomtheycanbeclassifiedunderthefollowingcategories:
Acoelomatesinwhichthecoelomisabsent.Coelomatesinwhichatruecoelomlinedbymesodermispresent.Pseudocoelomatesinwhichthecoelomisnotlinedbymesodermlayer.
Onthebasisofpresenceorabsenceofnotochordanimalscanbegroupedinto:
Non-chordates,theseorganismsdonothavenotochord.Chordates,theseorganismspossesnotochordatanystageoftheirlife.
Q.9. Howusefulisthestudyofthenatureofbodycavityandcoelomintheclassificationofanimals?
Solution: Thepresenceorabsenceofthebodycavityisimportantintheclassificationofanimalsasitindicatestheleveloforganizationinanevolutionarybasis.
Thebodycavitylinedwithmesodermiscalledcoelom.Theorganismspossessingcoelomarearthropods,molluscs,annelids,echinoderms,hemichordates,chordatesandtherefore,theyareknownascoelomates.Theyhaveacomplexstructureandanefficientorgansystemtocarryoutvariousprocesses.
Thebodycavitywithoutaliningofmesodermisknownasacoelomandtheseincludeloweranimalslikeplatyhelminthes.Therefore,theyareknownasacoelomatesandhavesimplebodyorganization.
Ifthemesodermisfoundasscatteredpouchesbetweenendodermandectodermsuchorganismsareknownaspseudocoelomates.Example:aschelminthes.Hence,intheanimalclassification,platyhelminthesarelessorganized,followedbyaschelminthes,whereas,annelids,arthropods,molluscs,echinoderms,hemichordates,andchordatesarewell-organizedtocarryoutdifferentactivities.
Q.10. Distinguishbetweenintracellularandextracellulardigestion?
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Solution: Feature IntracellularDigestion Extracellular digestion
Site It takes place insidethe cell.
It takes place outside the cell in thealimentary canal.
Feature IntracellularDigestion Extracellulardigestion
Enzymes
Onlyafewenzymesfromcytoplasmarereleasedintothefoodvacuole,wherefoodisdigested.
Well-definedcellssecreteenzymesandreleasethemintothecavityofthealimentarycanal.
Feature IntracellularDigestion Extracellulardigestion
Efficiency Thisisaless-efficientmethodofdigestionoffood.
Thisdigestionismoreefficient.
Feature IntracellularDigestion ExtracellulardigestionLeveloforganisation
Itoccursinunicellularorganisms.
Itoccursinmulticellularhighlyevolvedorganisms.
Feature IntracellularDigestion Extracellulardigestion
DistributionThedigestedfoodisreleasedintothecytoplasm.
Thedigestedfoodisabsorbedbythealimentarycanalandthendistributedindifferentpartsofthebody.
Q.11. Whatisthedifferencebetweendirectandindirectdevelopment?
Solution: Feature DirectDevelopment Indirectdevelopment
Presenceoflarva
Thereisnolarvalstageandtheembryodevelopsintoamatureorganismthatresemblestheparentorganism.
Inthistypeofdevelopment,theembryohatchesfromtheegginalarvalformbeforeitdevelopsintoamatureorganismthatresemblestheparentorganism.
Feature Direct Development Indirect development
Metamorphosis Metamorphosis isabsent. Metamorphosis is present.
Feature DirectDevelopment Indirectdevelopment
Example Observedinfishes,reptiles,birdsandmammals.
Observedinmostoftheinvertebratesandamphibians.
Q.12. Whatarethepeculiarfeaturesthatyoufindinparasiticplatyhelminthes?
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Solution: Platyhelminthesarethewormswithadorso-ventrallyflattenedbody,alsocalledasflatworms.Theyarefoundasparasitesinanimals,includinghumanbeings.e.g.Fasciolahepatica(liverfluke)andTaeniasolium(Tapeworm).
Theyhavethefollowingcharacteristicfeatures:
TheyaremostlyparasiticformsexceptforPlanariansandhavehooksandsuckers,whichhelpthemtoattachtothehostbody.Theyaretotallydependentonthehostfortheirnutrition.Theyarebilaterallysymmetrical,triploblasticandacoelomateswithorganlevelsofcellularorganization.Theyhaveanincompletedigestivesystem.i.etheypossessasingleopeningintheiralimentarycanalthatliesattheanteriorendandactsasbothmouthandanus.Theyhavespecializedcellsthathelpinexcretionandosmoregulationcalledflamecells.Theyarehermaphroditei.esexesarenotseparateandthefertilizationisinternalalthoughmanylarvalstagesarepresent.Theylacklocomotoryorgansduetotheirparasiticlifestyle.
Q.13. Whatarethereasonsthatyoucanthinkofforthearthropodstoconstitutethelargestgroupoftheanimalkingdom?
Solution: ArthropodaisthelargestphyluminthekingdomAnimaliaandincludealmosttwo-thirdofthenamedspeciesonearth.
Theyareknownfortheirjointedappendages,thathelptheminthemobilityonlandandenablethemtoescapefromtheenemy.Theirbodycomprisesthehead,thorax,andabdomenthatiscoveredbyanexoskeletonmadeofchitin,heteropolysaccharidesmadeofN-acetylglucosamineunits.Itprotectsthebodyfromdiverseatmosphericconditionsandalsopreventsthelossofwater,hencemakingthemadapttoterrestrialconditions.
Theyarethefirstorganismsthathaveawell-definedrespiratory,circulatory,anddigestivesystemthathelptheminsurvivalindiverseconditions.ThelargestnumberofspeciesintheanimalkingdomarefoundintheclassInsectaofphylumArthropoda.Theyareadaptabletoland,waterandairastheyhavewings.AllthesefactorscontributetothearthropodatoconstitutethelargestgroupofthekingdomAnimalia.
Q.14. Watervascularsystemisthecharacteristicofwhichgroupofthefollowing?PoriferaCtenophoraEchinodermata
Solution: ThewatervascularsystemisauniquefeatureofEchinoderms,whichhelpstheseorganismsinlocomotion,respiration,capturingandtransportationoffood.e.g.Starfish(Asterias),Seacucumber(Cucumaria).
Chordata
Q.15. “Allvertebratesarechordatesbutallchordatesarenotvertebrates”.Justifythestatement.
Solution: Chordataisthemostdevelopedamongallthephylumsintheanimalkingdom.Thecharacteristicfeaturesofchordataisthepresenceofthenotochord,pairedpharyngealgillslitsanddorsalhollownervecord,tailandaventralheart.
TheoccurrenceofthenotochordinsubphylaofChordata-
Urochordata(tunicate)-Itispresentonlyinthelarvaltail.Cephalochordata-Itispresentfromheadtothetailregionandstaysthroughoutitslife.Vertebrata-Itispresentonlyduringtheembryonicperiod,whichgetsreplacedwiththecartilaginousorbonyvertebralcolumnintheadults.
Thus,itconcludesthat“Allvertebratesarechordates,butallchordatesarenotvertebrates”.
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