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2006 Fossil Discovery of Early Tetrapod “Tiktaalik” “missing link” from sea to land animals Evidence Supporting Evolution AP Biology Evidence for Evolution • Paleontology – fossils show change in a species • • over time Biogeography – Similar species are found in similar ecosystems around the world Morphology – Comparing structures – – Homologous structures – body parts with similar structure but possible different function. Shows common ancestry Analogous structures – similar structure develops in organisms that share a common ecosystem but not a common ancestry • Biochemical or Molecular AP Biology – Similarities in gene sequences, proteins, DNA Fossils Preserved remains of living things Paleontology is the study of the fossil record Most organisms do not leave a fossil after death Explains the “missing links” Sedimentation Fossils AP Biology As the organism decomposes the spaces will be filled with the minerals from the silt The Archaeopteryx Fossil Reptilian Features Forelimb has three functional fingers with grasping claws. Lacks the reductions and fusions present in other birds. Breastbone is small and lacks a keel. True teeth set in sockets in the jaws. The hind-limb girdle is typical of dinosaurs, although modified. Long, bony tail. AP Biology Avian Features Vertebrae are almost flatfaced. Impressions of feathers attached to the forelimb. Belly ribs. Incomplete fusion of the lower leg bones. Impressions of feathers attached to the tail. LEFT: Archaeopteryx lithographica Found in 1877 near Blumenberg, Germany How old is that fossil? Relative Dating Age of fossils based according to their location in strata Absolute Dating Age of fossils determined by analyzing the content of radioactive isotopes found in the fossil. Half-life: The length of time required for half of the radioactive elements to change into another stable element. Unaffected by temperature, light, pressure, etc. All radioactive isotopes have a dependable half life. Ex: C14 decays into N14 AP Biology Relative Dating AP Biology Absolute Dating How radioactive “naturally occurring” elements get inside an organism: A.K.A – Radiometric dating AP Biology Homologous Structures Anatomical evidence AP Biology Analogous structures Convergent Don’t be fooled by evolution their looks! Those tails Does fins this & mean & sleek they bodies have a are recent common ancestor? analogous structures! Solving a similar problem with a similar solution AP Biology Molecular Homology Human Macaque Dog Bird Frog Lamprey The sequence in DNA proteins Why &compare is a &molecular DNA proteins record of evolutionary across species? relationships. Comparative hemoglobin structure 8 0 32 45 67 125 10 20 30 40 50 60 70 80 90 100 110 120 Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans AP Biology Vestigial organs Why would whales have pelvis & leg bones if they were always sea creatures? AP Biology These are remnants of structures that were functional in ancestral species Evolution evidence at the cellular level Domains: Archaea, Bacteria and Eukarya Elements conserved through all: DNA, RNA and many metabolic pathways. Eukaryotes – core features: Cytoskeleton Nucleus Membrane-bound organelles Linear chromosomes Endomembrane system AP Biology