2Phylogeny Historical relationship between organisms or lineages Ancestry shown by phylogenetic treePhylogenetic Systematics- shows relationships from past to presentShows evolutionary relationshipsFigure 2.1
4Cladistics Method for studying phylogeny Shows ancestry of derived featuresFigure 2.3Advanced structures are derived, synapomorphicPrimitive structures are not derived, ancestral, symplesiomorphic
5Convergence- organism response to similar environment Similar structures yet distantly related organismsEx: limbs of fishes and marine mammalsParallelism- structure similarities in closely related organismsSimilar morphology due to parallel evolutionEx: Dog and gray wolf skullFigure 2.4
6PaedomorphosisFigure (Left) larval state salamander with external, feathery gills; (Center) adult salamander that lost gills; (Right) adult axolotl salamander retains juvenile external gills.Paedomorphosis- Ontogenetic changes where larval features of ancestor becomes morphological features of descendantJuvenile character stage of ancestor is retained
7Paedomorphosis (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).
8Paedomorphosis (cont.) Neoteny- delayed rate of somatic developmentProgenesis- precocious sexual maturation in morphological juvenileBehavioral Paedomorphology- juvenile behavioral stage retainedEx: wolf pup and domestic dogHeterochrony- change in rates of character development during phylogeny
9Generalized- structure with broad function Ex: human handSpecialized- structure with restricted functionEx: single digit handModification- change from previous state, may be preadaptivePreadaptation- current trait that will be useful in futureEx: binocular vision and thumb
10Higher vs. Lower Vertebrates Amniotes- higher vertebrates with amniotic sacEx: reptiles, birds, mammalsAnamniotes- lower vertebrates without amniotic sacEx: fish, amphibiansAmnion- membrane sac that surrounds embryoCleidoic egg- amniotic egg with shell
11Serial homology- serial repetition of body parts in single organism Ex: SomitesFigure 2.7: Somite formation in 4 week old embryo.
12VestigialVestigial- phylogenetic remnant that was better developed in ancestor.(e.g., human appendix, fruit fly wings,python leg spurs)Figure 2.8: Ball python spurs.
13RudimentaryPhylogenetic sense- structure is fully exploited by a descendantEx: rudimentary lagena in fish (sac of semicircular canals) develops into organ of Corti in mammalsOntogenetic sense- structure is underdeveloped or not fully developed from embryo to adultEx: Muellerian tract in females develops into reproductive tract; yet in males, duct is rudimentaryEx: Woffian duct in males develops into sperm duct; yet in females, duct is rudimentary
14Adaptive Radiation- diversification of species into different lines through adaptation to new ecological nichesFigure 2.9: Branching evolution; increased diversity.
15Sea Squirt Free Swimming Larva Figure 2.10: Larval form of sea squirt.Figure 2.11: Lamprey larval structures.Larval stage of sea squirt resembles vertebrate tadpoleDeveloped notochord and dorsal nerve cordRudimentary brain and sense organs
16Sea Squirt Sessile Adult Figure 2.12: Adult sea squirt.Figure 2.13: Adult sea squirt structures (see book figure 3.4).Once larva attaches, notochord and nervous system disappearResembles invertebrate
17Literature CitedFigure 2.1-Figure 2.2-Figure 2.3- Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002.Figure 2.4-Figure 2.5-Figure 2.6- Morey, Darcy F. The Early Evolution of the Domestic Dog. American Scientist, Vol. 82, No. 4, p342.Figure 2.7-Figure 2.8-Figure 2.9-FigureFigureFigureFigure