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Ch. 15 Sec. 2

Ch. 15 Sec. 2. Ideas That Shaped Darwin's Thinking. Radical views Most people believed the Earth was only a few thousand years old Plants and animals were always the same. New discoveries Exploration Fossil record. I. An Ancient, Changing Earth.

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Ch. 15 Sec. 2

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  1. Ch. 15 Sec. 2 Ideas That Shaped Darwin's Thinking

  2. Radical viewsMost people believed the Earth was only a few thousand years oldPlants and animals were always the same

  3. New discoveriesExplorationFossil record

  4. I. An Ancient, Changing Earth James Hutton and Charles Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present

  5. A. Hutton and Geological Change • In 1795 - hypothesis • Geological forces • operate very slowly • over millions of years • ∴ Earth had to be much more than a few thousand years old

  6. B. Lyell's Principles of Geology • Stressed observation as explanation • Volcanoes • Canyons • Processes that shaped the Earth millions of years ago continue • Explained how geological features could be built up or torn down

  7. C. This understanding of geology influenced Darwin: • If the Earth could change over time, life might change as well. • It would have taken many years for life to change in the way Lyell suggested. This would have been possible only if the Earth were extremely old

  8. II. Lamarck's Evolution Hypotheses A. Jean-Baptiste Lamarck recognized that: • living things have changed over time • all species were descended from other species • organisms were adapted to their environments

  9. Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species.

  10. B. Tendency Toward Perfection  • Acquiring features that help them live more successfully in their environments • Birds fly because they wanted to fly

  11. C. Use and Disuse • Organisms could alter the size or shape of particular organs by using (or not using) their bodies in new ways • Traits then passed to offspring

  12. A male fiddler crab uses its front claw to ward off predators and to attract mates. • Lamarck's Hypothesis Fig.15 – 7 page 376

  13. Because the front claw is used repeatedly, it becomes larger. This characteristic (large claw) is passed onto its offspring.

  14. D. Inheritance of Acquired Traits E. Evaluating Lamarck's Hypothesis • Lamarck did not know: • how traits are inherited • that an organism’s behavior has no effect on its heritable characteristics • However, he paved the way for the work of later biologists

  15. III. Population Growth • 1798 - Thomas Malthus • Birth rate > Death rate • War, famine, and disease • Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.

  16. 2. When Darwin read Malthus’s work, he realized that this reasoning applied to plants and animals. 3. If all the offspring of almost any species survived for several generations, they would overrun the world. 4. This information was central to Darwin’s explanation of evolutionary change.

  17. 15–2 Ideas That Shaped Darwin’s Thinking In Darwin’s day, most Europeans thought that Earth and all of its life forms had existed for only a few thousand years. They also thought that species did not change. Some scientists of Darwin’s time began challenging these ideas. These scientists influenced the development of Darwin’s theory of evolution. • Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and that it had changed over time. These ideas helped Darwin realize that life might change as well. Knowing that Earth was very old convinced Darwin that there had been enough time for life to evolve.

  18. • Jean-Baptiste Lamarck was one of the first scientists to see that evolution occurred. He also recognized that organisms adapt to their environments. Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species. Scientists now know that some of Lamarck’s ideas are wrong. However, his general ideas about evolution and adaptation are correct. These ideas influenced Darwin.• Economist Thomas Malthus also influenced Darwin.Malthus thought that if the human population keptgrowing, sooner or later there would be insufficient living space and food for everyone. Darwin thought this was true for all organisms.

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