lecture02 - BioEE 278 Evolutionary Biology Fall 2007...

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BioEE 278 Fall 2007 Evolutionary Biology Lecture 2 EVIDENCE FOR EVOLUTION Chapter 3, pp. 48-55, 61-65 A. Darwin’s Fundamental Principles 1. Descent with modification 2. Hierachical organization 3. Good fit of organisms to environment B. Descent with modification and Homology 1. Most characters of organisms are modified from pre-existing characters of their ancestors . In other words, most characters do not arise “ de novo ”. 2. What do we mean by “character”? 3. Homology : homologous characters are ones that are inherited from an ancestor and have similar genetic and developmental underpinnings. a. Example (Fig. 3.4): limb bones of tetrapods (e.g., frogs, lizards, snakes, crocodiles, birds, mammals). b. Character “states” of homologous structures may differ. * in shape: bat vs. bird wings. * fusion or loss (horses). * “vestigial” or reduced limbs in snakes, hind limbs in whales, pseudogenes. 4. Existence of intermediate forms.
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lecture02 - BioEE 278 Evolutionary Biology Fall 2007...

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