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Chapter 15

Chapter 15. Evolution. Evolution:. The process by which modern organisms have descended from ancient organisms Change in a type of organism over time Favorable traits become more frequent in a population, while less favorable traits become less frequent. Puzzle of Life’s Diversity.

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Chapter 15

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  1. Chapter 15 Evolution

  2. Evolution: • The process by which modern organisms have descended from ancient organisms Change in a type of organism over time Favorable traits become more frequent in a population, while less favorable traits become less frequent

  3. Puzzle of Life’s Diversity • Voyage of the Beagle ( 1831 - 1836 ) • Charles Darwin • Traveled to the Galapagos Islands and around the world from England • Made numerous observations and collected evidence leading to his Theory of Natural Selection

  4. Darwin’s Observations • Collected 68 different beetle species in one day in the Brazilian rainforest • Observed different but similar species on different continents that had similar biomes • Collected Fossils from different continents ( some resembled living organisms, some were like nothing he had ever seen before ) • Shapes of tortoise shells varied from one Island to the next • Beaks of finches varied on each Island

  5. Ideas that Shaped Darwin’s Thinking • Most people believed that the Earth and its inhabitants were only a few thousand years old, and that they had not changed over that time • Fossil evidence was being collected, and interpreted as the demise of creatures from some great catastophe • Catastrophism

  6. Ancient and Changing Earth • James Hutton (1795) • Published a detailed hypothesis about the geological forces that shaped the Earth ( over millions of years ) -Charles Lyell (1830) - published “Principles of Geology” - proposed that the observable forces seen today are the same that acted in the past (uniformitarianism ) Jean-BaptisteLamark(1809) - organisms acquired or lost certain traits during their lifetime, these traits could be passed to offspring, over time this could lead to new species

  7. Thomas Malthus ( 1798 ) • Published that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone • - War, famine and disease work against this growth Darwin reasoned that this would be true of all species - but not all offspring survive, and not all survivors reproduce - Why???

  8. Darwin Presents His Case • Began filling notebooks with his ideas about species diversity and the process that would later be called evolution. • 1858 – he receives a short essay by Alfred Russel Wallace, summarizing thoughts on evolutionary change • 1859 – publishes “On the Origin of Species” • Proposed Natural Selection as the mechanism for evolution (descent with modification )

  9. Inherited Variation and Artificial Selection • Noted that members of each species vary from each other in important ways, and they could be inherited • Current thought was that the variations were not important • Artificial Selection • Nature provides the variation, and humans selected the variations they found useful

  10. Evolution by natural Selection • 1. the Struggle for existence • Members of a species compete for survival • 2. Survival of the Fittest ( natural selection ) • Fitness : ability of an individual to survive and reproduce in its specific environment • Adaptation: any inherited characteristic that increases an organism’s chance of survival • Changes increase the specie’s fitness in its environment • 3. Descent with Modification • Common Descent: all species were derived from common ancestors ( single “tree of life” links all living things )

  11. Evidence for Evolution • 1. Fossil Record • 2. Geographic Distributionof living species • 3. homologous body structures • 4. similarities in embryology

  12. Summary of Darwin’s Theory • 1. individual organisms differ, and some of this variation is inheritable • 2. organisms produce more offspring than survive, and some survivors do not reproduce • 3. organisms compete for limited resources • 4. successful organisms survive to reproduce and pass on characteristics to their offspring, this process causes speciation over time • 5. Modern species are descendents from a common ancestor

  13. Chapter Review • P. 389 # 1 – 10, 12, 14, 17, 18, 21 – 25 • P. 390 # 28 – 30, Writing in Science

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