Comparative Comparative AnatomyAnatomy

Concepts & PremisesConcepts & Premises

Note Set 1Note Set 1Chapters 1 & 2Chapters 1 & 2

PhylogenyPhylogeny

Historical Historical relationship relationship between organisms between organisms or lineagesor lineages

Ancestry shown by Ancestry shown by phylogenetic treephylogenetic tree

Phylogenetic Phylogenetic SystematicsSystematics- shows - shows relationships from relationships from past to presentpast to present Shows evolutionary Shows evolutionary

relationshipsrelationships Figure 2.1

Major Vertebrate GroupsMajor Vertebrate Groups

Figure 2.2

CladisticsCladistics Method for Method for

studying studying phylogenyphylogeny

Shows ancestry of Shows ancestry of derived featuresderived features

AdvancedAdvanced structures are derived, structures are derived, synapomorphicsynapomorphic

PrimitivePrimitive structures are not derived, structures are not derived, ancestral, symplesiomorphic ancestral, symplesiomorphic

Figure 2.3

ConvergenceConvergence- organism response to - organism response to similar environmentsimilar environment Similar structures yet distantly related Similar structures yet distantly related

organismsorganisms Ex: limbs of fishes and marine mammalsEx: limbs of fishes and marine mammals

ParallelismParallelism- structure similarities in - structure similarities in closely related organismsclosely related organisms Similar morphology due to parallel evolutionSimilar morphology due to parallel evolution

Ex: Dog and gray wolf skullEx: Dog and gray wolf skull

Figure 2.4

PaedomorphosisPaedomorphosis

PaedomorphosisPaedomorphosis- Ontogenetic changes - Ontogenetic changes where larval features of ancestor becomes where larval features of ancestor becomes morphological features of descendantmorphological features of descendant

Juvenile character stage of ancestor is Juvenile character stage of ancestor is retainedretained

Figure 2.5 - (Left) larval state salamander with external, feathery gills; (Center) adult salamander that lost gills; (Right) adult axolotl salamander retains juvenile external gills.

Paedomorphosis Paedomorphosis (cont.)(cont.)

Figure 2.6: Natural selection pressures on the wolf may have lead to the formation of a new species, the domestic dog. The prehistoric adult dog skull (center) can be compared to the adult wolf skull (left) and particularly the juvenile wolf skull (right).

NeotenyNeoteny- delayed rate of somatic - delayed rate of somatic developmentdevelopment

ProgenesisProgenesis- precocious sexual maturation - precocious sexual maturation in morphological juvenilein morphological juvenile

Behavioral PaedomorphologyBehavioral Paedomorphology- juvenile - juvenile behavioral stage retainedbehavioral stage retained

Ex: wolf pup and domestic dogEx: wolf pup and domestic dog

HeterochronyHeterochrony- change in rates of - change in rates of character development during phylogenycharacter development during phylogeny

Paedomorphosis Paedomorphosis (cont.)(cont.)

GeneralizedGeneralized- structure with broad function- structure with broad function Ex: human handEx: human hand

SpecializedSpecialized- structure with restricted - structure with restricted functionfunction

Ex: single digit handEx: single digit hand

ModificationModification- change from previous state, - change from previous state, may be preadaptivemay be preadaptive

PreadaptationPreadaptation- current trait that will be - current trait that will be useful in futureuseful in future

Ex: binocular vision and thumbEx: binocular vision and thumb

Amniotes- higher vertebrates with amniotic Amniotes- higher vertebrates with amniotic sac sac

Ex: reptiles, birds, mammalsEx: reptiles, birds, mammals

Anamniotes- lower vertebrates without Anamniotes- lower vertebrates without amniotic sacamniotic sac

Ex: fish, amphibiansEx: fish, amphibians

Amnion- membrane sac that surrounds Amnion- membrane sac that surrounds embryo embryo Cleidoic egg- amniotic egg with shellCleidoic egg- amniotic egg with shell

Higher vs. Lower Higher vs. Lower VertebratesVertebrates

Serial homology- serial repetition of Serial homology- serial repetition of body parts in single organismbody parts in single organism

Ex: SomitesEx: Somites

Figure 2.7: Somite formation in 4 week old embryo.

Vestigial- phylogenetic remnant that was better developed in ancestor.

(e.g., human appendix, fruit fly wings, python leg spurs)

Figure 2.8: Ball python spurs.

VestigialVestigial

RudimentaryRudimentary

Phylogenetic sensePhylogenetic sense- structure is fully - structure is fully exploited by a descendantexploited by a descendant

Ex: rudimentary Ex: rudimentary lagenalagena in fish (sac of semicircular in fish (sac of semicircular canals) develops into organ of Corti in mammalscanals) develops into organ of Corti in mammals

Ontogenetic senseOntogenetic sense- structure is - structure is underdeveloped or not fully developed underdeveloped or not fully developed from embryo to adultfrom embryo to adult

Ex: Ex: Muellerian tractMuellerian tract in females develops into in females develops into reproductive tract; yet in males, duct is rudimentaryreproductive tract; yet in males, duct is rudimentary

Ex: Ex: Woffian ductWoffian duct in males develops into sperm duct; in males develops into sperm duct; yet in females, duct is rudimentaryyet in females, duct is rudimentary

Adaptive RadiationAdaptive Radiation- diversification of - diversification of species into different lines through species into different lines through adaptation to new ecological nichesadaptation to new ecological niches

Figure 2.9: Branching evolution; increased diversity.

Sea Squirt Sea Squirt Free Swimming Larva Free Swimming Larva

Larval stage of sea squirt resembles Larval stage of sea squirt resembles vertebrate tadpolevertebrate tadpole Developed notochord and dorsal nerve cordDeveloped notochord and dorsal nerve cord Rudimentary brain and sense organsRudimentary brain and sense organs

Figure 2.10: Larval form of sea squirt.Figure 2.11: Lamprey larval structures.

Sea Squirt Sea Squirt Sessile AdultSessile Adult

Once larva attaches, notochord Once larva attaches, notochord and nervous system disappearand nervous system disappear Resembles invertebrateResembles invertebrate

Figure 2.13: Adult sea squirt structures (see book figure 3.4).

Figure 2.12: Adult sea squirt.

Literature CitedLiterature Cited

Figure 2.1- Figure 2.1- http://www.erin.utoronto.ca/~w3bio356/lectures/early_amniote.htmlhttp://www.erin.utoronto.ca/~w3bio356/lectures/early_amniote.html

Figure 2.2- http://courses.lib.odu.edu/biology/kcarpent/less10nte.html Figure 2.2- http://courses.lib.odu.edu/biology/kcarpent/less10nte.html Figure 2.3- Kardong, K. Vertebrates: Comparative Anatomy, Function, Figure 2.3- Kardong, K. Vertebrates: Comparative Anatomy, Function,

Evolution. McGraw Hill, 2002. Evolution. McGraw Hill, 2002. Figure 2.4- http://anthro.palomar.edu/animal/animal_2.htmFigure 2.4- http://anthro.palomar.edu/animal/animal_2.htmFigure 2.5- Figure 2.5-

http://evolution.berkeley.edu/evosite/evo101/IIIC6dDevochange2.shtmlhttp://evolution.berkeley.edu/evosite/evo101/IIIC6dDevochange2.shtmlFigure 2.6- Morey, Darcy F. The Early Evolution of the Domestic Dog. Figure 2.6- Morey, Darcy F. The Early Evolution of the Domestic Dog.

American Scientist, Vol. 82, No. 4, p342.American Scientist, Vol. 82, No. 4, p342.Figure 2.7- http://www.sciencemuseum.org.uk/exhibitions/lifecycle/12.aspFigure 2.7- http://www.sciencemuseum.org.uk/exhibitions/lifecycle/12.aspFigure 2.8- http://www.edwardtbabinski.us/articles/snake_vestigial_limb.htmlFigure 2.8- http://www.edwardtbabinski.us/articles/snake_vestigial_limb.htmlFigure 2.9- http://anthro.palomar.edu/animal/animal_1.htmFigure 2.9- http://anthro.palomar.edu/animal/animal_1.htmFigure 2.10- Figure 2.10-

http://www.umanitoba.ca/faculties/science/biological_sciences/lab13/http://www.umanitoba.ca/faculties/science/biological_sciences/lab13/biolab13_3.htmlbiolab13_3.html

Figure 2.11- http://cas.bellarmine.edu/tietjen/images/agnaths.htmFigure 2.11- http://cas.bellarmine.edu/tietjen/images/agnaths.htmFigure 2.12- http://www8.nos.noaa.gov/coris_glossary/index.aspx?letter=aFigure 2.12- http://www8.nos.noaa.gov/coris_glossary/index.aspx?letter=aFigure 2.13- Figure 2.13-

http://www.auburn.edu/academic/classes/zy/0301/Topic3/Topic3.htmlhttp://www.auburn.edu/academic/classes/zy/0301/Topic3/Topic3.html