2 Phylogeny Historical relationship between organisms or lineages Ancestry shown by phylogenetic treePhylogenetic Systematics- shows relationships from past to presentShows evolutionary relationshipsFigure 2.1
4 Cladistics Method for studying phylogeny Shows ancestry of derived featuresFigure 2.3Advanced structures are derived, synapomorphicPrimitive structures are not derived, ancestral, symplesiomorphic
5 Convergence- 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
6 PaedomorphosisFigure (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
7 Paedomorphosis (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).
8 Paedomorphosis (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
9 Generalized- 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
10 Higher 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
11 Serial homology- serial repetition of body parts in single organism Ex: SomitesFigure 2.7: Somite formation in 4 week old embryo.
12 VestigialVestigial- phylogenetic remnant that was better developed in ancestor.(e.g., human appendix, fruit fly wings,python leg spurs)Figure 2.8: Ball python spurs.
13 RudimentaryPhylogenetic 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
14 Adaptive Radiation- diversification of species into different lines through adaptation to new ecological nichesFigure 2.9: Branching evolution; increased diversity.
15 Sea 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
16 Sea 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
17 Literature 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