15–2 Ideas That Shaped Darwin's Thinking Photo credit: Art Wolfe Incorporated Copyright Pearson Prentice Hall

An Ancient, Changing Earth How did Hutton and Lyell describe geological change?

An Ancient, Changing Earth Hutton and 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. Copyright Pearson Prentice Hall

An Ancient, Changing Earth Lyell's Principles of Geology Lyell stressed that scientists must explain past events in terms of processes that they can actually observe. The processes that shaped the Earth millions of years earlier continue in the present. Copyright Pearson Prentice Hall

An Ancient, Changing Earth 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. Copyright Pearson Prentice Hall

Lamarck’s Evolution Hypotheses According to Lamarck, how did species evolve? Copyright Pearson Prentice Hall

Lamarck's Evolution Hypotheses Jean-Baptiste Lamarck recognized that: living things have changed over time. all species were descended from other species. organisms were adapted to their environments. Copyright Pearson Prentice Hall

Lamarck's Evolution Hypotheses 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. Flaws: Tendency toward perfection Use and Disuse Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Lamarck’s Evolution Copyright Pearson Prentice Hall

Lamarck's Evolution Hypotheses Lamarck's Hypothesis A male fiddler crab uses its front claw to ward off predators and to attract mates. Lamarck proposed that the selective use or disuse of an organ led to a change in that organ that was then passed on to offspring. This proposed mechanism is shown here applied to fiddler crabs. (1) The male crab uses its small front claw to attract mates and ward off predators. (2) Because the front claw has been used repeatedly, it becomes larger. Copyright Pearson Prentice Hall

Lamarck's Evolution Hypotheses Lamarck's Hypothesis Because the front claw is used repeatedly, it becomes larger. This characteristic (large claw) is passed onto its offspring. Copyright Pearson Prentice Hall

Lamarck's Evolution Hypotheses Evaluating Lamarck's Hypotheses Lamarck’s hypotheses of evolution are incorrect in several ways. 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. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall August Weismann Disproves the idea of inheritance of acquired traits by cutting off the tails of mice for 5 generations. All mice gave birth to mice with tails. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall What was Malthus's theory of population growth? Population Growth Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Population Growth Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. Copyright Pearson Prentice Hall

Early Ideas About Evolution There were many important naturalists in the 18th century. Linnaeus: classification system from kingdom to species Buffon: species shared ancestors rather than arising separately E. Darwin: more-complex forms developed from less-complex forms Lamarck: environmental change leads to use or disuse of a structure Copyright Pearson Prentice Hall 18

Early Ideas About Evolution Theories of geologic change set the stage for Darwin’s theory. There were three theories of geologic change. Copyright Pearson Prentice Hall 19

Copyright Pearson Prentice Hall Catastrophism Natural disasters such as floods and volcanic eruptions have shaped landforms and caused species to become extinct. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Gradualism Changes is landform resulted from slow changes over a long period of time. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Uniformitarianism The geologic processes that shape Earth are uniform through time. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall 15–2 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 15–2 Hutton and Lyell recognized that geological processes of the past differ from those of the present. indicate that Earth is many millions of years old. operate quickly, often over thousands of years. always involve violent events like volcanoes, earthquakes, and floods. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 15–2 The discovery of many fossils challenged the idea that acquired traits could be inherited. Earth is many millions of years old. species had never changed over time. geological changes are slow. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 15–2 Which of the following scientists proposed the hypothesis of selective use and disuse? Charles Darwin Jean-Baptiste Lamarck Thomas Malthus Charles Lyell Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 15–2 The scientist that proposed that Earth is shaped by geological forces that took place over long periods of time is: Malthus Hutton Darwin Lamarck Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 15–2 Darwin’s reading of Thomas Malthus made him realize that because of overpopulation, human beings cannot avoid extinction. all living things must evolve. living things produce more offspring than can possibly survive. the basic ideas of Lamarck were wrong. Copyright Pearson Prentice Hall

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