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Bio242LaboratoryModule2

Theme:Evolutionshapestheflowandpatternofinformationthroughphylogeneticlineages,evidentinthe

linkagebetweenformandfunction

Objectives-wewilltracktheeffectsofnaturalselectiononthelineages

oflifeastheyadapttolifeonland-wewillcomparethedifferentadaptationsofhomologous

featuresamonglineages-wewillusethevariationamonghomologouslocitoreconstructthephylogenyofthelineagesoflife

Bio242Lab6

UnderstandingBiologicalDiversity:SystematicTheoryandPractice

• Brief introduction toKingdom Animalia• Examineform andfunction ofMolluscamorphology, especiallyfeatures thatenabledlifeonland.

• Usecomputer software (Mesquite) toassembleaphylogenyofthe molluscs andtesthypotheses ofevolution

Whatisananimal?

• Without looking atyournotes, anythoughts?

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Whatisananimal?

• Multicellularheterotrophs:feedbyingestion.

• Howdoesthisdifferfromplants,fungi,protists?

Whatisananimal?

• Carbohydratesstoredasglycogen

• Polysaccharideofglucose

• (no,youdonotneedtoknowthisstructure)

Whatisananimal?

• Nocellwalls• Cellssupportedbystructuralproteins:collagen– Extracellularmatrix,supportstissues,givescellsstructurefromoutside

– Triple-helixstructuralprotein

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Whatisananimal?

• Nerveandmuscletissue

• Impulse&movement

Whatisananimal?ComplexEmbryo• Egg+Sperm⎝• Zygote⎝cleavage ⎝• Blastula⎝• Gastrula⎝• Larvaorjuvenile⎝• Adult

Notethetwolayersoftissueatthegastrulastage(EctodermandEndoderm)

The complexembryoand germlayerdevelopment

• Diploblastic:Animalswithonlyectodermandendoderm

• Cnidaria (jellies)andCtenophora(combjellies)

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Gastrulation

• Allbilateralanimalshaveathirdgermlayer,themesoderm

• Formsmusclesandmostorgansbetweendigestivetractandtheoutercovering.

• Triploblastic

BodyCavity:TheCoelom

• Mosttriploblasticanimalshaveabodycavity– Fluid- orair-filledspaceseparatingthedigestivetractfromtheouterbodywall.

• Thisisthecoelom

BodyCavity:TheCoelom

• Thecoelomformsfromtissuederivedfrommesoderm

• COELOMATES:– Mesodermconnectsdorsallyandventrallyandprovidesacompletelining ofthecoelom

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BodyCavity:TheCoelom

• Thecoelomformsfromtissuederivedfrommesoderm

• PSEUDO-COELOMATES:– Coelomislinedwithmesoderm(outside)andendoderm(inside)

BodyCavity:TheCoelom

• Thecoelomformsfromtissuederivedfrommesoderm

• ACOELOMATES:– Notruebodycavity– Oftensoft-bodiedorganisms.

Morphological Trends

Tissues• PoriferaorParazoa(sponges)lacktruetissues(thisisauniquedevelopment)

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Morphological Trends

Symmetry• Radialvsbilateral• Radial– Topandbottomonly--noleftorright

– Likelyancestral trait:Cnidarians,Ctenophores

PoriferaMetazoa

ANCESTRALPROTIST

CtenophoraEum

etazoa

Deuterostom

ia

670 millionyears ago

Bilateria

Lophotrochozoa

Ecdysozoa

Cnidar ia

Acoela

Hemichordata

Echinodermata

Chordata

Platyhelminthes

Syndermata

Ectoprocta

Brachiopoda

Mollusca

Annelida

Nematoda

Arthropoda

770 millionyears ago

680 millionyears ago

Cellular level/no tissues; asymmetric;skeleton of spiculesandspongin

Bilateralsymmetry;cephalization;triploblastic;bodycavities(coelom)

Multicellular;heterotrophic;complexembryo;nocellwall

Truetissues;diploblastic;radialsymmetry

TrendsintheevolutionofAnimalia

TheMolluscs

• >100,000 species (second onlytothearthropods innumbers)

• Mostlymarine, but 8,000infreshwater• 28,000 spp.ofsnails andslugsliveonland• reduced coelom• Similar bodyplan, butmodified invariousways:foot, visceralmass,mantle, shell, andradula

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ThelineagesofMollusca

• Gastropods (snailsandslugs)• Polyplacophorans (chitons)• Bivalves(clams,scallops, mussels)• Cephalopods (octopus, squid, nautilus)• Scaphopods (tooth ortuskshells)

Gastropods

Bivalves

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Polyplacophorans

Scaphopods

Cephalopods

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Visceralmass

Clamdissectiondetails

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Mouth?Anus?

Scallopsanyone?

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