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Evidence for macroevolution Strongest = Fossil Record order of fossils in sediments oldest at bottom date with radioisotopes. Fossil Record Find successive change in groups of organisms: "missing links" whale legs & shape. Fossil Record - PowerPoint PPT Presentation
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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