#2 - Evolution Background

#2 - Evolution Background - What Produces Biodiversity...

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1 What Produces Biodiversity? EVOLUTION “In considering the Origin of Species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well-founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which most justly excites our admiration.” -- Charles Darwin , The Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life (1859) So what IS evolution anyway? • Definition 1 : any change in the frequency of alleles in a gene pool (population) from one generation to the next. • In other words, if the proportion of alleles of any particular gene changes from one generation to the next, EVOLUTION HAS OCCURRED! The Theory of Evolution • Definition 2 : Evolution is “descent with modification” from a common ancestor, resulting in changes in the features of organisms across generations. The processes of evolution may result in the formation of new species (and/or traits of a given species) and the loss of others. • The Theory : The processes which contribute to descent with modification are responsible for generating ALL BIOLOGICAL DIVERSITY EVER .
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2 How do the different definitions fit together? • Evolution explains changes in traits that are inherited from generation to generation. We now know that changes in genes in a population are responsible for these changes in traits. x Thus, the processes which alter gene pools from one generation to the next are responsible for generating ALL BIOLOGICAL DIVERSITY, including traits, species, major groups of organisms, etc. A Powerful Theory • The Theory of Evolution provides a framework for forming hypotheses to answer questions about any aspect of biodiversity Proximate explanations deal with how a specific phenomenon works. I.e., “How does it work?” • e.g., How does a bat’s wing allow it to fly? • e.g., How does a particular type of pneumonia bacteria resist a particular antibiotic? Ultimate explanations focus on how a phenomenon came to exist in a particular way. I.e., “Why does it work the way it does, as opposed to some other way?” • e.g., How did bats come to have wings, and why are their wing’s different from those of birds, or insects? • e.g., Why do bacteria often exhibit resistance to antibiotics
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This note was uploaded on 04/24/2008 for the course BIOL 216 taught by Professor Baker during the Spring '08 term at Clark University.

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#2 - Evolution Background - What Produces Biodiversity...

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