Evidence for macroevolution Strongest = Fossil Record• order of fossils in sediments• oldest at bottom• date with radioisotopes

Fossil RecordFind successive change in groups of organisms: "missing links"• whale legs & shape

Fossil RecordFind successive change in groups of organisms: "missing links"• whales• horse size

Fossil RecordFind successive changes: "missing links"• whale legs & shape• horse size• hominid cranium

Evidence for macroevolutionDNA: many genes are so similar that they must have diverged from a common ancestor:

Align genes, count diffs

Evidence for macroevolutionDNA: many genes are so similar that they must have diverged from a common ancestor

Align genes, count diffs# changes says when 2 spp. split

Molecular clocksAlign genes, count diffs# changes tells when 2 spp. splitCalibrate with fossil record

Mitochondrial DNA traces Mom• only comes from mom & doesn’t recombine• says we split ~ 170,000 years agoY chromosome traces Dad• only comes from dad & doesn’t recombine•Says we entered Europe ~ 50,000 years ago

Evidence for macroevolutionFossil recordDNAComparative anatomy: same bones derived from common ancestor: shape & function has changed

Evidence for macroevolutionFossil recordDNAComparative anatomy: same bones derived from common ancestor: shape & function changed

Vestigial structures: non-functional left-overs

Evidence for macroevolutionFossilsDNAComparative anatomyEmbryos retrace evolution as they develop

Embryos retrace phylogenyEmbryos retrace evolution as they develop

Embryos retrace phylogenyEmbryos retrace evolution as they developClose spp lookalike longer

Convergent evolution similar selection results in organisms that look alike e.g. desert plants: American cacti & African euphorbs look alike but unrelated

Convergent evolution similar selection -> organisms look alike e.g. Australian marsupials resemble American placental mammals

Convergent evolution similar selection -> organisms look alike e.g. Australian marsupials resemble American placental MammalsFill same niche:role in nature

Analogy vs homologyAnalogous: look alike but different originBird vs insect wings

Analogy vs homologyAnalogous: look alike but different originBird vs insect wingsfins vs flippers

Analogy vs homologyAnalogous: look alike but diff origin• Bird vs insect wings• fins vs flippersHomologous: look different, same origin

Pace of evolutionSome plants evolve rapidlyMammals evolve slowlyStarfish evolve very slowly

Pace of evolutionGradualism: gradual evolutionLarge populationsSlow change in selection

Pace of evolutionGradualism: gradual evolution

Large populationsSlow change in selection

Punctuated equilibria: evolve in spurts

Pace of evolutionPunctuated equilibria: evolve in spurtssmall populationsGenetic drift alters gene poolRapidly adapt then reach equilibrium

Pace of evolutionMass extinctions:

O2 poisoning 2 b.y.a. killed most bacteria

Mass extinctionsO2 poisoning 2 b.y.a. killed most bacteria96% of species died at end of PermianAsteroid 65 m.y.a. killed dinosaurs

Mass extinctionsO2 poisoning 2 b.y.a. killed most bacteria96% of species died at end of Permian: asteroid?Asteroid 65 m.y.a. killed dinosaursMan is causing another mass extinction!Enable evolution of new spp!

Mass extinctionsEnable evolution of new spp!Formerly occupied niches become availablemajor factor in success of mammals