AnimalDiversityAnimalDiversityBIOL221

Ch.32

• 1.3millionlivingspeciesofanimals

• havebeeniden;fied

• Thereareexcep;onstonearlyeverycriterionfor

dis;nguishinganimalsfromotherlife‐forms

• Severalcharacteris;cs,takentogether

• sufficientlydefinethegroup

Characteris2csofAnimalsCharacteris2csofAnimals

Nutri2on,CellStructureandSpecializa2onNutri2on,CellStructureandSpecializa2on

• Animals

• heterotrophsthatingesttheirfood

• mul;cellulareukaryotes

• lackcellwalls

• bodiesareheldtogetherbystructural

proteins

• suchascollagen

• Nervous;ssueandmuscle;ssue

• uniquetoanimals

Reproduc2onandDevelopmentReproduc2onandDevelopment

• Mostanimalsreproducesexually

• diploidstagedominateslifecycle

• AMeraspermfer;lizesanegg

• zygoteundergoesrapidcelldivision

• calledcleavage

• subdivision

• leadstoblastula

• undergoesgastrula2on

• formingagastrula

• withdifferentlayersofembryonic;ssues

Fig.Fig. 32‐2‐132‐2‐1

Zygote

Cleavage

Eight-cell stage

Fig.Fig. 32‐2‐232‐2‐2

Zygote

Cleavage

Eight-cell stage

Cleavage Blastula

Cross sectionof blastula

Blastocoel

Fig.Fig. 32‐2‐332‐2‐3

Zygote

Cleavage

Eight-cell stage

Cleavage Blastula

Cross sectionof blastula

BlastocoelGastrulation

BlastoporeGastrula

Archenteron

Ectoderm

Endoderm

Blastocoel

Video

• Manyanimals

• haveatleastonelarvalstage

• larva

• sexuallyimmatureand

morphologicallydis;nctfromtheadult

• eventuallyundergoes

metamorphosis

Reproduc2onandDevelopmentReproduc2onandDevelopment

• Allanimals,andonlyanimals

• haveHoxgenes

• regulatethedevelopmentofbodyform

• Hoxfamilyofgeneshasbeenhighlyconserved

• butcanproduceawidediversityofanimalmorphology

Reproduc2onandDevelopmentReproduc2onandDevelopment

HalfabillionyearsofAnimalsHalfabillionyearsofAnimals

• Theanimalkingdomincludesgreatdiversityoflivingspecies

• evengreaterdiversityofex;nctones

• Commonancestoroflivinganimals

• mayhavelivedbetween675and875millionyearsago

• mayhaveresembledmodernchoanoflagellates

• pro;ststhataretheclosestlivingrela;vesof

animals

Fig.Fig. 32‐332‐3

OTHEREUKARYOTES

Choanoflagellates

Sponges

Other animals

Anim

als

Individualchoanoflagellate

Collar cell(choanocyte)

NeoproterozoicEra(1BillionNeoproterozoicEra(1Billion––524MillionYearsAgo)524MillionYearsAgo)

• Earlymembersoftheanimal

fossilrecord

• Ediacaranbiota

• 565to550million

yearsago

Fig.Fig. 32‐432‐4

(a) Mawsonites spriggi (b) Spriggina floundersi

1.5 cm 0.4 cm

PaleozoicEra(542PaleozoicEra(542––251MillionYearsAgo)251MillionYearsAgo)

• Cambrianexplosion(535to525

millionyearsago)

• earliestfossilappearanceof

manymajorgroupsofliving

animals

• Severalhypothesesregardingthe

causeoftheCambrianexplosion

• Newpredator‐preyrela;onships

• Ariseinatmosphericoxygen

• Theevolu;onoftheHoxgene

complex

Fig.Fig. 32‐532‐5

AnimalDiversityAnimalDiversity• Animaldiversity

• con;nuedtoincreasethroughthePaleozoic

• butpunctuatedbymassex;nc;ons

• begantomakeanimpactonland

• by460millionyearsago

• Vertebratesmadethetransi;ontoland

• around360millionyearsago

MesozoicEra(251MesozoicEra(251––65.5MillionYearsAgo)65.5MillionYearsAgo)

• Coralreefsemerged

• becomingimportantmarineecologicalnichesforotherorganisms

• Dinosaurswerethedominantterrestrialvertebrates

• Firstmammalsemerged

CenozoicEra(65.5MillionYearsAgotothePresent)CenozoicEra(65.5MillionYearsAgotothePresent)• ThebeginningoftheCenozoicera

• followedmassex;nc;onsofbothterrestrialandmarineanimals

• Theseex;nc;onsincludedthelarge

• nonflyingdinosaursandthemarinerep;les

• Modernmammalordersandinsects

• diversifiedduringtheCenozoic

AnimalscanbecharacterizedbyAnimalscanbecharacterizedby““bodyplansbodyplans””

• Zoologists

• some;mescategorizeanimalsaccordingtoabody

plan

• asetofmorphologicalanddevelopmentaltraits

• Agrade

• agroupwhosememberssharekeybiologicalfeatures

• notnecessarilyaclade,ormonophyle;cgroup

SymmetrySymmetry

• Animalscanbecategorized

• accordingtothesymmetryoftheirbodies

• orlackofit

• Someanimalshave

• radialsymmetry

• Pieslicesarethesame

• bilateralsymmetry

• Two‐sidedsymmetry

• Adorsal(top)sideandaventral(bo`om)side

• ArightandleMside

• Anterior(head)andposterior(tail)ends

• Cephaliza2on,thedevelopmentofahead

Fig.Fig. 32‐732‐7

(a) Radial symmetry

(b) Bilateral symmetry

TissuesTissues

• Animalbodyplans

• alsovaryaccordingtotheorganiza;onoftheanimal’s;ssues

• Tissues

• collec;onsofspecializedcells

• isolatedfromother;ssuesbymembranouslayers

• Duringdevelopment

• threegermlayersgiverisetothe;ssuesandorgansoftheanimalembryo

• Ectoderm,mesoderm,endoderm

• Ectoderm

• thegermlayercoveringtheembryo’ssurface

• Endoderm

• innermostgermlayer

• linesthedevelopingdiges;vetube

• calledthearchenteron

• Diploblas2c

• animalshaveectodermandendoderm

• Triploblas2c

• animalsalsohaveaninterveningmesodermlayer

• theseincludeallbilaterians

GermLayersGermLayers

BodyCavi2esBodyCavi2es

• Mosttriploblas;canimals

• possessabodycavity

• Atruebodycavity

• calledacoelom

• derivedfrom

mesoderm

• Coelomates

• animalsthatpossessa

truecoelom

Fig.Fig. 32‐8a32‐8a

CoelomBody covering(from ectoderm)

Digestive tract(from endoderm)

Tissue layerlining coelomand suspendinginternal organs (from mesoderm)

(a) Coelomate

• pseudocoelom

• bodycavityderived

fromthemesodermand

endoderm

• Notlinedby

mesodermonall

sides

• pseudocoelomates

• Triploblas;canimals

thatpossessa

pseudocoelom

BodyCavi2esBodyCavi2es

Fig.Fig. 32‐8b32‐8b

Pseudocoelom

Body covering(from ectoderm)

Muscle layer(frommesoderm)

Digestive tract(from endoderm)

(b) Pseudocoelomate

• acoelomates

• Triploblas;canimalsthatlackabodycavityarecalled

BodyCavi2esBodyCavi2es

(c) Acoelomate

Body covering(from ectoderm)

Wall of digestive cavity(from endoderm)

Tissue-filled region(from mesoderm)

ProtostomeandDeuterostomeDevelopmentProtostomeandDeuterostomeDevelopment

• Basedonearlydevelopment

• manyanimalscanbecategorized

• ashavingprotostomedevelopment

• ordeuterostomedevelopment

CleavageCleavage

• protostomedevelopment

• cleavageisspiralanddeterminate

• deuterostomedevelopment

• cleavageisradialandindeterminate

• indeterminatecleavage

• eachcellintheearlystagesofcleavage

• retainsthecapacitytodevelopintoacompleteembryo

• makespossibleiden;caltwins,andembryonicstemcells

Fig.Fig. 32‐932‐9

Protostome development(examples: molluscs,

annelids)

Deuterostome development(examples: echinoderm,

chordates)

Eight-cell stage Eight-cell stage

Spiral and determinate Radial and indeterminate

Coelom

Archenteron

(a) Cleavage

(b) Coelom formation

Coelom

KeyEctodermMesodermEndoderm

Mesoderm MesodermBlastopore BlastoporeSolid masses of mesodermsplit and form coelom.

Folds of archenteronform coelom.

Anus Mouth

Digestive tube

Mouth AnusMouth develops from blastopore. Anus develops from blastopore.

(c) Fate of the blastopore

CoelomForma2onCoelomForma2on

• Inprotostomedevelopment

• splibngofsolidmassesofmesodermformsthe

coelom

• Indeuterostomedevelopment

• mesodermbudsfromthewallofthearchenteronto

formthecoelom

Fig.Fig. 32‐9b32‐9b

Coelom

Protostome development(examples: molluscs,

annelids)

Deuterostome development(examples: echinoderms,

chordates)

(b) Coelom formation

KeyEctodermMesodermEndoderm

MesodermMesodermCoelom

Archenteron

Blastopore BlastoporeSolid masses of mesodermsplit and form coelom.

Folds of archenteronform coelom.

FateoftheBlastoporeFateoftheBlastopore

• Theblastopore

• formsduringgastrula;on

• connectsthearchenterontotheexteriorofthegastrula

• Inprotostomedevelopment

• blastoporebecomesthemouth

• Indeuterostomedevelopment

• blastoporebecomestheanus

Fig.Fig. 32‐9c32‐9c

Anus

Protostome development(examples: molluscs,

annelids)

Deuterostome development(examples: echinoderms,

chordates)

Anus

Mouth

Mouth

Digestive tube

(c) Fate of the blastopore

KeyEctodermMesodermEndoderm

Mouth develops from blastopore. Anus develops from blastopore.

AnimalphylogenyfrommoleculardataAnimalphylogenyfrommoleculardata

• Zoologists

• recognizeaboutthreedozenanimalphyla

• Currentdebateinanimalsystema;cs

• hasledtothedevelopmentoftwophylogene;chypotheses

• butothersexistaswell

• Onehypothesisofanimalphylogeny

• isbasedmainlyonmorphologicalanddevelopmental

comparisons

• Anotherhypothesisofanimalphylogeny

• isbasedmainlyonmoleculardata

Fig.Fig. 32‐1032‐10

ANCESTRALCOLONIALFLAGELLATE

Metazoa Eum

etazoa

“Porifera”

Bilateria

Deuterostom

iaProtostom

ia

Cnidaria

Ctenophora

Ectoprocta

Brachiopoda

Echinodermata

Chordata

Platyhelminthes

Rotifera

Mollusca

Annelida

Arthropoda

Nematoda

Fig.Fig. 32‐1132‐11

Silicea

ANCESTRALCOLONIALFLAGELLATE

Metazoa

Eumetazoa

“Porifera”B

ilateria

Deuterostom

iaLophotrochozoa

Ecdysozoa

Calcarea

Ctenophora

Cnidaria

Acoela

Echinodermata

Chordata

Platyhelminthes

Rotifera

Ectoprocta

Brachiopoda

Mollusca

Annelida

Nematoda

Arthropoda

PointsofAgreementPointsofAgreement

• Allanimalsshareacommonancestor

• Spongesarebasalanimals

• Eumetazoaisacladeofanimals(eumetazoans)

• withtrue;ssues

• MostanimalphylabelongtothecladeBilateria

• calledbilaterians

• Chordatesandsomeotherphyla

• belongtothecladeDeuterostomia

ProgressinResolvingBilaterianRela2onshipsProgressinResolvingBilaterianRela2onships

• Themorphology‐basedtree

• dividesbilateriansintotwoclades

• deuterostomesandprotostomes

• Incontrast,recentmolecularstudies

• indicatethreebilaterianclades

• Deuterostomia,Ecdysozoa,andLophotrochozoa

• Ecdysozoans

• shedtheirexoskeletonsthroughaprocesscalledecdysis

Fig.Fig. 32‐1232‐12

• Somelophotrochozoans

• haveafeedingstructurecalledalophophore

• Otherphylagothroughadis;nctdevelopmentalstage

• calledthetrochophorelarva

ProgressinResolvingBilaterianRela2onshipsProgressinResolvingBilaterianRela2onships

Fig.Fig. 32‐1332‐13

LophophoreApical tuftof cilia

Mouth

(a) An ectoproct (b) Structure of a trochophore larva

100 µm

Anus

FutureDirec2onsinAnimalSystema2csFutureDirec2onsinAnimalSystema2cs

• Phylogene;cstudies

• basedonlargerdatabases

• willlikelyprovidefurtherinsightsintoanimal

evolu;onaryhistory

Youshouldnowbeableto:Youshouldnowbeableto:

1. Listthecharacteris;csthatcombinetodefineanimals

2. SummarizekeyeventsofthePaleozoic,Mesozoic,andCenozoiceras

3. Dis;nguishbetweenthefollowingpairsorsetsofterms:radialandbilateralsymmetry;gradeandcladeofanimaltaxa;diploblas;candtriploblas;c;spiralandradialcleavage;determinateandindeterminatecleavage;acoelomate,pseudocoelomate,andcoelomategrades

4. Comparethedevelopmentaldifferencesbetweenprotostomesanddeuterostomes

5. Comparethealternaterela;onshipsofannelidsandarthropodspresentedbytwodifferentproposedphylogene;ctrees

6. Dis;nguishbetweenecdysozoansandlophotrochozoans

Youshouldnowbeableto:Youshouldnowbeableto: