Half a century after darwin published his theory

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Half a century after Darwin published his theory, scientists discovered radioactivity Scientists now use radioactivity to establish the age of rocks and fossils Radioactive dating indicates that the earth is about 4.5 billion years old , which supports Darwin’s idea that the Earth was very old
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The Age of Earth and Fossils Recent Fossil Finds During Darwin’s time, not enough intermediate fossils had been found to document the evolution of modern species from their ancestors Since Darwin, paleontologists have discovered hundreds of fossils that identify intermediate stages in the evolution of many different groups of modern species Exs: Whales Dinosaurs Birds Fish Four-Legged Animals
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Comparing Anatomy and Embryology In Darwin’s time, scientists noted that all vertebrate limbs had the same basic bone structure But some were used for crawling, some for climbing, some for running and others for flying
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Homologous Structures Same Structure, Different Function What does it show? Evidence of a common ancestor
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Darwin proposed that animals with similar structures evolved from a common ancestor with a basic version of that structure Similarities and differences among homologous structures help determine how recently species shared a common ancestor Homologous structures have also been found in plants Homologous Structures
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The clue to common descent is common structure , not common function NOT inherited from a common ancestor. Analogous Structures Body parts that share a common function , but not structure Same function, Different structure Exs. – The wing of a bee and the wing of a bird Analogous Structures
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Analogous Structures
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Vestigial Structures Vestigial structures are those structures that are similar but are reduced in size and remain unused Humans have a vestigial structure. Can you name it?
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Vestigial pelvis and femur in a modern whale.
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Vestigial Structures
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Embryology Embryology is the study of the early stages of development of an organism Researchers noticed a long time ago that vertebrate embryos look very similar The same groups of embryonic cells develop in the same order and in similar patterns
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Embryology Vertebrate embryos have fold of tissue in the neck region called gill pouches In fish these develop into gills In human these same pouches develop to form inner ear bones .
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Lines of Evidence: Molecular Evidence Similarities in early development suggest a common ancestor Embryology
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Embryology
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Embryology
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Genetics and Molecular Biology Biochemists study and compare chemicals found in living things ( DNA and Proteins ) The genetic code is nearly identical in almost all organisms This is powerful evidence that all organisms evolved from common ancestors that shared this code
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DNA Sequencing
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