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16.2 – Ideas That Shaped Darwin’s Thinking Warm Up How did Lamarck propose organisms evolve? Explain this process. 16.2 – Ideas That Shaped Darwin’s Thinking Chapter 16: Darwin’s Theory of Evolution 16.2 – Ideas That Shaped Darwin’s Thinking Think about it! Many Europeans in Darwin’s time believed the Earth was only a few thousand years old!! Darwin’s ideas relied upon the Earth being much older. He based these thoughts off of the research by several scientists. 16.2 – Ideas That Shaped Darwin’s Thinking James Hutton and Geological Change Recognized connections between a number of geological processes and geological features. Proposed two main ideas 1. Forces from under the Earth’s surface can push rock layers up to create mountains. 2. Wind and water erosion can wear mountains away and create valleys. (Grand Canyon – Rocky Mountains) 16.2 – Ideas That Shaped Darwin’s Thinking James Hutton’s Conclusion All of these process took very long time to occur! Concluding that the Earth must be much older than a few thousand years. 16.2 – Ideas That Shaped Darwin’s Thinking Lyell’s Principles of Geology Stated that the laws of nature are constant over time and past events can be explained by current observations! Examples Ancient volcanoes released lava and gases, just as volcanoes do now. Ancient rivers slowly dug channels and carved canyons in the past, just as they do today. 16.2 – Ideas That Shaped Darwin’s Thinking Lyell’s Conclusion Lyell agreed with Hutton Argued that Earth was much older than a few thousand years Lyell’s book significantly impacted Darwin’s thinking. 16.2 – Ideas That Shaped Darwin’s Thinking Lamarck’s Evolutionary Hypotheses Jean-Baptiste Lamarck also proposed that species change over time: The Principle of Inherited Characteristics That organisms could change during their lifetimes by selectively using or not using various parts of their bodies. He also suggested that individuals could pass these acquired traits on to their offspring! 16.2 – Ideas That Shaped Darwin’s Thinking Lamarck’s Ideas Example A giraffe with a 3’ long neck can only reach the leaves at the bottom of the tree. After it ate all of the leaves at the bottom it has to continuously reach for higher leaves. Reaching for the higher leaves all of the time caused its neck to grow longer. Now it can easily reach the higher leaves. The giraffe will then pass the long neck trait on to its offspring. Principle of Inherited Characteristics 16.2 – Ideas That Shaped Darwin’s Thinking Evaluating Lamarck’s Hypotheses Today, we know that Lamarck’s hypotheses were incorrect in several ways. Evolution does not progress in a predetermined direction. Traits acquired by individuals during their lifetime cannot be passed on to offspring. 16.2 – Ideas That Shaped Darwin’s Thinking Population Growth Thomas Malthus – English Economist Conducted human population studies. Noted the that there were more births than deaths. This increased population would create competition for resources! 16.2 – Ideas That Shaped Darwin’s Thinking Population Growth Darwin knew that Malthus’s idea of competition applied animals as well. Examples: A oak tree can produce thousands of seeds each summer. One oyster can produce millions of eggs each year. Most offspring die before reaching maturity, and only a few of those that survive manage to reproduce. 16.2 – Ideas That Shaped Darwin’s Thinking Artificial Selection Artificial Selection = nature provides the variations, and humans select the traits they find useful. Darwin put artificial selection to the test by raising and breeding fancy pigeon varieties. 16.2 – Ideas That Shaped Darwin’s Thinking Artificial Selection Darwin concluded that natural variation provided the raw material for evolution. When Darwin published his scientific explanation for evolution, it changed the way people understood the living world.