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Unformatted text preview: Principles of Biology II - Leege Georgia Southern University Descent with Modifications I. Themes of Biology: Diversity and Evolution Dazzling diversity: 1.5 million species described 5-100 million present II. Evolution Link between unity and diversity Why study evolution? Species diversity Adaptations for survival Similarities and differences among species Patterns in fossil record Geographic distribution of species All these patterns are explained by evolution! III. What is evolution? A. Evolution = Change in genetic makeup of a population over time. Change Genetic makeup Population Time Not an external change in structure Does not occur to individuals B. How does change take place? Mechanism of evolution: 2 step process Heritable variation in population Differential reproductive success How do we know variation is heritable? i. Types of variation Variation as response to environment Genetic variation Figure 23.11 How can we tell genetic and environmental variation apart?...
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