NCERT Solutions | Class IX | Science (Biology) | Chapter 7 | Diversity in Living Organisms

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1. NCERT
SOLUTIONS
BIOLOGY
CLASS –IX

2. Diversity in Living
Organisms

3. In-text Exercise 1
Whydoweclassifyorganisms?
Thereareawiderangeoflifeforms(about10million−13million
species)aroundus.Theselifeformshaveexistedandevolvedonthe
Earthovermillionsofyearsago.Thehugerangeoftheselifeforms
makesitverydifficulttostudythemonebyone.Therefore,welookfor
similaritiesamongthemandclassifythemintodifferentclassestostudy
thesedifferentclassesasawhole.Thus,classificationmakesourstudy
easier.
Examplesofrangeofvariationsobservedindailylifeare:
i.Varietyoflivingorganismsintermsofsizerangesfrommicroscopic
bacteriatotalltreesof100metres.
ii.Thecolour,shape,andsizeofsnakesarecompletelydifferentfrom
thoseoflizards.
iii.Thelifespanofdifferentorganismsisalsoquitevaried.For
example,acrowlivesforonly15years,whereasaparrotlivesfor
about140years.
BiswarupMajumder| Bio-World
1.
2.Givethreeexamplesoftherangeofvariationsthatyouseein
life-formsaroundyou.

4. BiswarupMajumder| Bio-World
Theprimarycharacteristiconwhichthefirstdivisionoforganismsis
madeisthenatureofthecell.Itisconsideredtobethefundamental
characteristicforclassifyingalllivingorganisms.Natureofthecell
includesthepresenceorabsenceofmembrane-boundorganelles.
Therefore,onthebasisofthisfundamentalcharacteristic,wecan
classifyalllivingorganismsintotwobroadcategoriesofeukaryotesand
prokaryotes.Then,furtherclassificationismadeonthebasisof
cellularityormodesofnutrition.
2.
Thekindofcellsthatlivingorganismsaremadeupofisamorebasic
characteristicforclassifyingorganisms,thanonthebasisoftheir
habitat.Thisisbecauseonthebasisofthekindofcells,wecanclassify
alllivingorganismsintoeukaryotesandprokaryotes.Ontheotherhand,
ahabitatortheplacewhereanorganismlivesisaverybroad
characteristictobeusedasthebasisforclassifyingorganisms.For
example,animalsthatliveonlandincludeearthworms,mosquitoes,
butterfly,rats,elephants,tigers,etc.Theseanimalsdonotresemble
eachotherexceptforthefactthattheyshareacommonhabitat.
Therefore,thenatureorkindofacellisconsideredtobeafundamental
characteristicfortheclassificationoflivingorganisms
.
Whatistheprimarycharacteristiconwhichthefirstdivisionof
organismsismade?
In-text Exercise 2
Whichdoyouthinkisamorebasiccharacteristicforclassifying
organisms?
a)theplacewheretheylive.
b)thekindofcellstheyaremadeof.Why?
1.
B
(B)
(A)
A

5. Plantsandanimalsdifferinmanyfeaturessuchastheabsenceof
chloroplasts,presenceofcellwall,etc.But,locomotionisconsideredas
thecharacteristicfeaturethatseparatesanimalsfromplants.Thisis
becausetheabsenceoflocomotioninplantsgaverisetomany
structuralchangessuchasthepresenceofacellwall(forprotection),
thepresenceofchloroplasts(forphotosynthesis)etc.Hence,
locomotionisconsideredtobethebasiccharacteristicasfurther
differencesarosebecauseofthischaracteristicfeature.
BiswarupMajumder| Bio-World
1.
Aprimitiveorganismorlowerorganismistheonewhichhasasimple
bodystructureandancientbodydesignorfeaturesthathavenot
changedmuchoveraperiodoftime.Anadvancedorganismorhigher
organismhasacomplexbodystructureandorganization.Forexample,
anAmoebaismoreprimitiveascomparedtoastarfish.Amoebahasa
simplebodystructureandprimitivefeaturesascomparedtoastarfish.
Hence,anAmoebaisconsideredmoreprimitivethanastarfish.
Whichorganismsarecalledprimitiveandhowarethey
differentfromtheso-calledadvancedorganisms?
2.
In-text Exercise 3
Willadvancedorganismsbethesameascomplexorganisms?
Why?
3.Onwhatbasesareplantsandanimalsputintodifferent
categories?
Itisnotalwaystruethatanadvancedorganismwillhaveacomplex
bodystructure.But,thereisapossibilitythatovertheevolutionary
time,complexityinbodydesignwillincrease.Therefore,attimes,
advancedorganismscanbethesameascomplexorganisms.
StarfishAmoeba

6. Thecriterionfortheclassificationoforganismsbelongingtokingdom
MoneraorProtistaisthepresenceorabsenceofawell-definednucleus
ormembrane-boundorganelles.KingdomMoneraincludesorganisms
thatdonothaveawell-definednucleusormembrane-boundorganelles
andtheseareknownasprokaryotes.KingdomProtista,ontheother
hand,includesorganismswithawell-definednucleusandmembrane-
boundorganellesandtheseorganismsarecalledeukaryotes.
BiswarupMajumder| Bio-World
Inthehierarchyofclassification,whichgroupingwillhavethe
smallestnumberoforganismswithamaximumof
characteristicsincommonandwhichwillhavethelargest
numberoforganisms?
3.
Inthehierarchyofclassification,aspecieswillhavethesmallestnumber
oforganismswithamaximumofcharacteristicsincommon,whereas
thekingdomwillhavethelargestnumberoforganisms.
Inwhichkingdomwillyouplaceanorganismwhichissingle-
celled,eukaryoticandphotosynthetic?
2.
KingdomProtistaincludessinglecelled,eukaryotic,andphotosynthetic
organisms.
In-text Exercise 5
In-text Exercise 4
1.Whatisthecriterionforclassificationoforganismsas
belongingtokingdomMoneraorProtista?
Whichdivisionamongplantshasthesimplestorganisms?1.
Thallophytaisthedivisionofplantsthathasthesimplestorganisms.This
groupincludesplants,whichdonotcontainawelldifferentiatedplant
body.Theirbodyisnotdifferentiatedintoroots,stems,andleaves.They
arecommonlyknownasalgae.

7. BiswarupMajumder| Bio-World
Howarepteridophytesdifferentfromthephanerogams?2.
Howdogymnospermsandangiospermsdifferfromeach
other?
3.
Around 85 percent plant kingdom is
found in the ocean, among which 75
percent plants are undefined.

8. BiswarupMajumder| Bio-World
Howdoporiferananimalsdifferfromcoelenterateanimals?1.
Howdoannelidanimalsdifferfromarthropods?2.
In-text Exercise 6
Whatarethedifferencesbetweenamphibiansandreptiles?3.
Whatarethedifferencesbetweenanimalsbelongingtothe
Avesgroupandthoseinthemammaliagroup?
4.

9. Inbiology,hierarchyreferstothetaxonomicalclassificationofliving
organismsinsuccessivelevelsofcomplexity.“Kingdom”isthehighestrank
insuchaclassificationwhile“species”isthelowest.
BiswarupMajumder| Bio-World
NCERT Exercise
Whataretheadvantagesofclassifyingorganisms?1.
Thereareawiderangeoflifeforms(about10million-13millionspecies)
aroundus.TheselifeformshaveexistedandevolvedontheEarthover
millionsofyearsago.Thehugerangeoftheselifeformsmakesitvery
difficulttostudythemonebyone.Therefore,welookforsimilarities
amongthemandclassifythemintodifferentclassessothatwecan
studythesedifferentclassesasawhole.Thismakesourstudyeasier.
Therefore,classificationservesthefollowingadvantages:
a)Itdeterminesthemethodsoforganizingthediversityoflifeon
Earth.
b)Ithelpsinunderstandingmillionsoflifeformsindetail.
c)Italsohelpsinpredictingthelineofevolution.
Howwouldyouchoosebetweentwocharacteristicstobeused
fordevelopingahierarchyinclassification?
2.
Fordevelopingahierarchyofclassification,wechoosethefundamental
characteristicamongseveralothercharacteristics.Forexample,plants
differfromanimalsintheabsenceoflocomotion,chloroplasts,cellwall,
etc.But,onlylocomotionisconsideredasthebasicorfundamental
featurethatisusedtodistinguishbetweenplantsandanimals.Thisis
becausetheabsenceoflocomotioninplantsgaverisetomany
structuralchangessuchasthepresenceofacellwallforprotection,and
thepresenceofchloroplastforphotosynthesis(astheycannotmove
aroundinsearchoffoodlikeanimals).Thus,allthesefeaturesarea
resultoflocomotion.Therefore,locomotionisconsideredtobea
fundamentalcharacteristic.Bychoosingthebasicorfundamental
characteristic,wecanmakebroaddivisionsinlivingorganismsasthe
nextlevelofcharacteristicisdependentonthese.Thisgoesontoforma
hierarchyofcharacteristics.

10. BiswarupMajumder| Bio-World
Explainthebasisforgroupingorganismsintofivekingdoms.3.
R.H.Whittakerproposedafivekingdomclassificationoflivingorganisms
onthebasisofLinnaeus’systemofclassification.Thefivekingdoms
proposedbyWhittakerareMonera,Protista,Fungi,Plantae,and
Animalia.Thebasisforgroupingorganismsintofivekingdomsisas
follows:
a)Onthebasisofthepresenceorabsenceofmembrane-bound
organelles,alllivingorganismsaredividedintotwobroadcategories
ofeukaryotesandprokaryotes.Thisdivisionleadtotheformationof
kingdomMonera,whichincludesallprokaryotes.
b)Then,eukaryotesaredividedasunicellularandmulticellular,onthe
basisofcellularity.UnicellulareukaryotesformkingdomProtista,
andmulticellulareukaryotesformkingdomFungi,Plantae,and
Animalia.
c)Animalsarethenseparatedonthebasisoftheabsenceofacell
wall.
d)Sincefungiandplantsbothcontainacellwall,theyareseparated
intodifferentkingdomsonthebasisoftheirmodesofnutrition.
Fungihavesaprophyticmodeofnutrition,whereasplantshave
autotrophicmodeofnutrition.Thisresultsintheformationofthe
fivekingdoms.

11. BiswarupMajumder| Bio-World
WhatarethemajordivisionsinthePlantae?Whatisthebasis
forthesedivisions?
4.
ThekingdomPlantaeisdividedintofivemaindivisions:Thallophyta,
Bryophyta,Pteridophyta,Gymnosperms,andAngiosperms.
Theclassificationdependsonthefollowingcriteria:
Differentiated/Undifferentiatedplantbody
Presence/Absenceofvasculartissues
With/Withoutseeds
Nakedseeds/Seedsinsidefruits
a)Thefirstlevelofclassificationdependsonwhetheraplantbodyiswell
differentiatedornot.Agroupofplantsthatdonothaveawell
differentiatedplantbodyareknownasThallophyta.
b)Plantsthathavewelldifferentiatedbodypartsarefurtherdividedon
thebasisofthepresenceorabsenceofvasculartissues.Plantswithout
specialisedvasculartissuesareincludedindivisionBryophyta,whereas
plantswithvasculartissuesareknownasTracheophyta.
c)Tracheophytaisagainsub-dividedintodivisionPteridophyta,onthe
basisoftheabsenceofseedformation.
d)Theothergroupofplantshavingwelldevelopedreproductiveorgans
thatfinallydevelopseedsarecalledPhanerogams.Thisgroupisfurther
sub-dividedonthebasisofwhethertheseedsarenakedorenclosed
infruits.Thisclassifiesthemintogymnospermsandangiosperms.
Gymnospermsareseedbearing,non-floweringplants,whereas
angiospermsarefloweringplantsinwhichtheseedsareenclosed
insidethefruit.

12. BiswarupMajumder| Bio-World
Howarethecriteriafordecidingdivisionsinplantsdifferent
fromthecriteriafordecidingthesubgroupsamonganimals?
5.
Criteriafordecidingdivisionsinplantsare:
i.Differentiated/Undifferentiatedplantbody
ii.Presence/Absenceofvasculartissues
iii.With/Withoutseeds
iv.Nakedseeds/Seedsinsidefruits
KingdomAnimaliaisdividedintotwomajorgroupsonthebasisofthe
presenceorabsenceofanotochord.

13. BiswarupMajumder| Bio-World
Non-chordatesdonotpossessanotochord,whileallmembersofthe
phylumchordatespossessanotochord.
Non-chordateisfurtherdividedintosubgroupsonthebasisofthe
followingfeatures:
Onthebasisoftheabovefeatures,non-chordatesaredividedintothe
followingsubgroups:
Porifera,
Coelenterate,
Platyhelminthes,
Nematodes,
Annelids,
Molluscs,
Arthropoda,and
Echinodermata.

14. BiswarupMajumder| Bio-World
Allmembersofthephylumchordatepossessanotochord.However,
someanimalssuchasBalanoglossus,Amphioxus,Herdmania,etc.have
anotochord,whichiseitherabsentordoesnotruntheentirelengthof
theanimal’sbody.Therefore,theseanimalsarekeptinaseparatesub-
phylumcalledProtochordata,andtherestofthechordatesareincluded
inthesub-phylumvertebrata.Themembersofthesub-phylum
vertebrataareadvancedchordates.Theyaredividedintofiveclasses:
Pisces,Amphibian,Reptilia,Aves,andMammalia.

15. BiswarupMajumder| Bio-World
i.ClassPisces:Thisclassincludesfishsuchastuna,rohu,shark,etc.
Theseanimalsmostlyliveinwater.Hence,theyhavespecial
adaptivefeaturessuchasastreamlinedbody,presenceofatailfor
movement,gills,etc.toliveinwater.
ii.ClassAmphibia:Itincludesfrogs,toads,andsalamanders.These
animalshaveadualmodeoflife.Inthelarvalstage,therespiratory
organsaregills,butintheadultstage,respirationoccursthrough
thelungsorskin.Theylayeggsinwater.
iii.ClassReptilia:Itincludesreptilessuchaslizards,snakes,turtles,
etc.Theyusuallycreeporcrawlonland.Thebodyofareptileis
coveredwithdryandcornifiedskintopreventwaterloss.Theylay
eggsonland.
iv.ClassAves:Itincludesallbirdssuchassparrow,pigeon,crow,etc.
Mostofthemhavefeathers.Theirforelimbsaremodifiedinto
wingsforflight,whilehindlimbsaremodifiedforwalkingand
clasping.Theylayeggs.
v.ClassMammalia:Itincludesavarietyofanimalswhichhavemilk
producingglandstonourishtheiryoungones.Somelayeggsand
somegivebirthtoyoungones.Theirskinhashairaswellassweat
glandstoregulatetheirbodytemperature.
ExplainhowanimalsinVertebrataareclassifiedintofurther
subgroups.
6.
AnimalsinVertebrataareclassifiedintofiveclasses:
Vertebrata