Darwins observations lamarcks evolutionary hypotheses

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Darwin’s Observations
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Lamarck’s Evolutionary Hypotheses Proposed that the use or disuse of organs caused organisms to gain or lose traits over time. These new characteristics could be passed on to the next generation .
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Ex. - A water bird’s long legs happen because the animal kept wading in deeper water to get food.
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Lamarck’s hypotheses were incorrect in many ways We know that traits acquired during a lifetime cannot be passed on to offspring Evaluating Lamarck’s Hypotheses
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However, Lamarck was one of the first to: Suggest that species are not fixed Explain that evolution uses natural processes Recognize that there is a link between an organism’s environment and its body structures Lamarck’s work paved the way for later biologists, including Darwin Evaluating Lamarck’s Hypotheses
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Population Growth In 1798, Thomas Malthus noticed that people were being born faster than people were dying He reasoned that if the human population grew unchecked, there would not be enough living space and food for everyone The forces that work against human population growth are war, famine and disease
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How this helped Darwin He reasoned that what Malthus proposed for human populations also applied to all living things. He observed that most organisms produce many more offspring than survive . He wondered which individuals would survive . . . and why If all the offspring that were produced did survive, they would overrun the world.
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To find an explanation for change in nature, Darwin studied the changes produced by plant and animal breeders Some plants bear larger or smaller fruits than others Some cows give more or less milk than others in their herd This told Darwin that variation could be passed from parents to offspring and used to improve crops and livestock Artificial Selection
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In artificial selection , nature provides the variations, and humans select the ones they find useful Darwin knew that variation occurs in wild species as well as domesticated species He realized that that natural variation provided the raw material for evolution Artificial Selection
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Artificial Selection
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16-3 Darwin Presents His Case Darwin wanted to gather as much evidence as he could to support his ideas before he made them public In 1858, Darwin read an essay by Alfred Wallace whose thoughts about evolution were almost identical to his! In order to not get “scooped”, Darwin decided to present his work at a scientific meeting in 1858 along with some of Wallace’s essay The next year, Darwin published his complete work on evolution: On the Origin of Species
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Evolution by Natural Selection Struggle for Existence From Malthus’ theory of supply and demand , Darwin reasoned that if more individuals are produced than can survive , they will have to compete for food, living space and other necessities of life Darwin described this as the struggle for existence
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Evolution by Natural Selection Variation and Adaptation Individuals have natural variations among their inheritable traits Some variations are
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