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Evolution

Evolution. Chapter 7 and 8. Theory of Evolution. Process by which populations accumulate inherited changes over time Change over time. What is a Theory?. An explanation for an observation or a series of observations that is supported by a considerable body of evidence. Evidence of Evolution.

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Evolution

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  1. Evolution Chapter 7 and 8

  2. Theory of Evolution • Process by which populations accumulate inherited changes over time • Change over time

  3. What is a Theory? • An explanation for an observation or a series of observations that is supported by a considerable body of evidence.

  4. Evidence of Evolution • Fossil Record • Vestigial Structures • Comparing Organisms • Skeletal Structures • DNA • Embryonic Stages

  5. Fossil Record • Fossils are the remains or imprints of once-living organisms found in the layers of the Earth’s crust • Fossil provide a sequence of evolutionary events known as the fossil record

  6. Vestigial Structures • Remnants of once useful structures • Example – Modern whales do not have legs, however they do have remnants of hind limb bones • Modern Boa Constrictors also have remnant legs

  7. Evolution of Whales http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html

  8. Comparing Organisms

  9. Charles Darwin • Darwin was a naturalist (scientist who studies nature) • He collected samples and learned about the world on his Voyage of the Beagle

  10. Darwin’s Finches and the Galapagos Islands • Darwin’s most famous encounter was on the Galapagos where he observed animals and plants that were very similar, yet showed great variation

  11. Historical Contributions • Darwin lived during a time of great discovery • Scientist soon realized that the earth was very old, old enough for great changes to have occurred • Thomas Malthus observed that if populations continue to grow, at some point there will be insufficient resources, food and living space Hutton Lyell

  12. Change Over Time • Darwin began developing his theory in 1836, but he did not publish until 1858 out of fear • It took the discoveries of Alfred Wallace to encourage Darwin to publish is work “On the Origin of Species”

  13. Natural Selection • Overproduction – Species produce more offspring than can survive to maturity • Variation – Individuals in a population have slight differences. Some traits will increase that an individual will survive to reproduce • Struggle to Survive – Not enough resources to support all individuals  Competition • Successful Reproduction – Individuals who are best adapted to survive and reproduce  Reproducing more of their successful trait

  14. Speciation • If two groups become separated and have unique environmental pressures, overtime the two populations can become so different that they can no longer interbreed • Species that cannot interbreed are considered different species

  15. Separation

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