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7.2

7.2. Evidence for Evolution. Fossil Evidence Texas fossils proved it was once covered by sea Kinds of Fossils Fossil – any evidence of life from an earlier geological time. Imprint of a leaf, feather, or organism in rock

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7.2

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  1. 7.2 Evidence for Evolution

  2. Fossil Evidence • Texas fossils proved it was once covered by sea • Kinds of Fossils • Fossil – any evidence of life from an earlier geological time

  3. Imprint of a leaf, feather, or organism in rock • Cast made of minerals that fills in the follows of an animal track, mollusk shell, or other parts of an organism • A piece of wood or bond replaced by minerals • An organism frozen in ice • An insect or other organism trapped in amber • Sedimentary Rock – a rock type formed from particles of preexisting rocks

  4. The Fossil Record • Scientists developed a geologic Time Scale • Relative Dating • Estimate of how old a fossil is • Based on the idea that the lower it is, the older it will be. • Radiometric Dating • Radioactive elements – give off radiation due to an unstable nucleus • Compares radioactive to non radioactive material to determine dating • Several samples to obtain consistent results • Uranium

  5. Fossils Show Evolution Occurred • Simple life forms from past times • Other Evidence for Evolution • Homologous – body parts that are similar in origin and structure • Homologous structures indicate that two or more species might share a common ancestor • Dolphin flipper and bird wing

  6. Vestigial Structures • Vestigial structure – a body part that doesn’t seem to have a function • Whales and snakes with hip bones • Embryology • Embryology – study of the development in organisms • Gills in all mammals

  7. DNA • Closely related organisms have similar DNA • Bears and Dogs • All primates have a common ancestor • Share hemoglobin, a protein in red blood cells that carries oxygen

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