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Evidence for Evolution by Natural Selection Regents Biology 2006-2007 What is evolution? Evolution is the gradual change in a species over time. Regents Biology Isn’t evolution just a theory? A theory is a well-supported ____________, testable _______, explanation of phenomena that have occurred in the natural world, like the theory of __________________, gravitational attraction cell ________, theory and _____________. atomic theory Regents Biology http://www.avgoe.de/StarChild/DOCS/STARCH00/questions/apple_falling.gif http://sixthsense.osfc.ac.uk/chemistry/atomic_structure2/atom.gif Evidence supporting evolution Fossil record Anatomical record Molecular record Regents Biology 1. Fossil record Fossils show a series of organisms have lived on Earth over a long period of time Regents Biology Fossils tell a story… the Earth is old Life is old Life on Earth has changed Regents Biology Evolution of birds Today’s organisms descended from ancestral species Fossil of Archaeopteryx lived about 150 mya links reptiles & birds Regents Biology We found the fossil! Land Mammal ? ? ? Complete series of transitional fossils Someone’s idea of a joke! Regents ButBiology the joke’s on them!! Ocean Mammal ? 2. Anatomical record Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors Regents Biology Compare the bones The same bones under the skin limbs that perform different functions are built from the same bones How could these very different animals have the same bones? Regents Biology Homologous structures Structures that come from the same origin homo- = same -logous = information Forelimbs of human, cats, whales, & bats same structure on the inside different functions on the outside evidence of common ancestor Regents Biology Vestigial organs Hind leg bones on whale fossils Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land! Regents Biology Vestigial organs Structures on modern animals that have no function remains of structures that were functional in ancestors evidence of change over time some snakes & whales have pelvis bones & leg bones of walking ancestors eyes on blind cave fish human tail bone Regents Biology Comparative embryology Development of embryo tells an evolutionary story similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development Regents Biology 3. Molecular record Comparing DNA & protein structure everyone uses the same genetic code (DNA)! Human Macaque Dog Bird Frog Lamprey 8 32 45 67 125 compare common genes compare common proteins 0 10 20 30 40 50 60 70 80 90 100 110 120 Regents Biology Building “family” trees Closely related species are branches on the tree — coming from a common ancestor Regents Biology Rate Yourself 4 Apply concepts of natural selection and evolution by creating a scenario that demonstrates the ideas 3 Explain how natural selection leads to evolution. 2 Describe how the evidence supports evolution. 1 Identify evidence for evolution. Regents Biology