Chapter 22 -Descent with Modification - A Darwinian View of Life

Chapter 22 -Descent with Modification - A Darwinian View of Life

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AP Biology ROOSEVELT HIGH SCHOOL Dr. Block Chapter 22 Descent with Modification: A Darwinian View of Life Lecture Outline Overview On November 24, 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection. Darwin’s book drew a cohesive picture of life by connecting what had once seemed a bewildering array of unrelated facts. Darwin made two major points in The Origin of Species: 1. Today’s organisms descended from ancestral species that were different from modern species. 2. Natural selection provided a mechanism for this evolutionary change. ° The basic idea of natural selection is that a population can change over time if individuals that possess certain heritable traits leave more offspring than other individuals. ° Natural selection results in evolutionary adaptation, an accumulation of inherited characteristics that increase the ability of an organism to survive and reproduce in its environment. Eventually, a population may accumulate enough change that it constitutes a new species. In modern terms, we can define evolution as a change over time in the genetic composition of a population. ° Evolution also refers to the gradual appearance of all biological diversity. Evolution is such a fundamental concept that its study is relevant to biology at every level, from molecules to ecosystems. ° Evolutionary perspectives continue to transform medicine, agriculture, biotechnology, and conservation biology. Student Misconceptions 1. Many first-year students misunderstand the vitally important theory of evolution by natural selection. One problem is that many  of the biological terms associated with evolution have familiar, everyday meanings that are different from their strict biological  definitions. The following terms may be problematic: n Fitness.  When students think of fitness, they usually think of an organism’s general health, vigor, strength, or intelligence. As a  result, they may find it hard to appreciate that any trait that increases an organism’s relative reproductive success increases its  fitness. n Adaptation.  In everyday use, adaptation refers to an individual changing over its lifetime in response to the environment.  Students may confuse the colloquial and scientific meanings of this term and arrive at the mistaken notion that changes  (“adaptations”) over individual lifetimes accumulate to bring about evolutionary change in populations. n Theory.  Students may tell you, “Evolution is only a theory, not a fact.” In common usage, the term  theory  means a tentative  explanation. In a scientific context, a theory is a useful, comprehensive, and well-supported explanation for a wide range of  observations. n
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This note was uploaded on 02/18/2011 for the course BIO 211 taught by Professor Powell during the Spring '10 term at Portland CC.

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Chapter 22 -Descent with Modification - A Darwinian View of Life

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