lec16bio100Evolution

lec16bio100Evolution - Evolution The Story Behind the...

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Evolution The Story Behind the Theory
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Evidence of Evolution Evolution has two different meanings to biologists. The term can refer to either a process or a theory. A theory is a general principle that explains or predicts observations. Generally, the word evolution means change, and the process of biological evolution relates to this definition.
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Evidence of Evolution Biological evolution is a change in the characteristics of a population of organisms over many generations. An evolutionary change is one that results in a change in the frequency of alleles in a population. Evolution has been observed many times, and we can even infer that it has occurred in the past.
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Evidence of Evolution The theory of evolution is a principle for understanding how species come into being and why they have the characteristics they exhibit.
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Evidence of Evolution Species on earth today are descendants of a single common ancestor, and all species represent the product of millions of years of evolutionary change. In other words, modern organisms, humans included, are related to each other and have been diverging from their common ancestor by a variety of processes since life originated.
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Evidence of Evolution When scientists think about evolution , they think about the origin of modern species from a common ancestor ( theory of common descent ). Figure 22.1 Figure 22.1
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Which evolutionary tree is correct?
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Evidence of Evolution Figure 22.2 Figure 22.2
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Evidence of Evolution Darwin was especially influenced by the month he spent on the Galapagos Islands. He found many birds, reptiles and other organisms that appeared to be unique to each island. Most noteworthy for Darwin were the giant tortoises.
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Evidence of Evolution Figure 22.3 Figure 22.3
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The Theory of Evolution by Natural Selection Charles Darwin and Alfred Russell Wallace (1858) state the Theory of Evolution: All species past and present are related by descent from a common ancestor Species change through time (“descent with modification”).
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Past Contributors and Disciplines Ideas of evolution can be traced back to the time of early Greek philosophers Thomas Malthus: Political Economist Charles Lyell: “Father of Geology” Georges Cuvier: Paleontologist MAIN IDEAS: comparative organismal biology & fossils in rocks of extinct species Jean-Baptiste de Lamarck: Zoologist MAIN IDEAS: organisms change individually (incorrect), and pass on their traits to their offspring (correct)
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Natural Selection Species are related by common ancestry. The characteristics of a species can be
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lec16bio100Evolution - Evolution The Story Behind the...

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