Chapter 1 - Chapter 1=Adaptaion by Natural Selection...

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Chapter 1=Adaptaion by Natural Selection Darwin’s Theory of Adaptation (The struggle for existence, variation in fitness, and the inheritance of variation) 1. The ability of a population to expand is infinite, environmental support is finite (because sources are finite, not all individuals will be able to survive and reproduce; organisms reproduce until environment can no longer sustain them) 2. Organisms within populations vary, and this variation allows for survival and reproduction (some will possess traits that help them reproduce more successfully-adaptations) 3. This variation is transmitted from parent to offspring (inherited) (If traits heritable they will be passed on to offspring and be more common in successive generations) Natural Selection-evolution by variation and selective retention An Example of Adaptation by Natural Selection *Finches Supply of food was not sufficient to sustain population; beak depth varied among finches and affected bird’s survival (large beaked birds ^ small beaked birds decreased; average beak depth increased (small beaked birds died) Morphology-an organism’s size, shape and composition Selection preserves the status quo when the most common type is best adapted (birds with large beaks less likely to survive juvenile period-require more food) Equilibrium-‘neither gene frequencies nor phenotypes change Stabilizing selection-process that produces equilibrium Populations characteristics susceptible to change as well =) Species-dynamic population of individuals that may or may not change over time Stasis/not natural state of species but prevalent when the most favored type is most common-favored by stabilizing selection INDIVIDUAL SELECTION Adaptation results from the competition among individuals, not between the entire populations or species Selection produces adaptation that benefits individuals (often selection leads to changes in behavior/morphology that increase the reproductive success of individuals but decreases that of the group, population, species) *organisms produce more offspring than necessary to maintain species (individual vs. group)
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This note was uploaded on 08/26/2011 for the course ANTHRO 200 taught by Professor Gouzoulesandkonner during the Spring '11 term at Emory.

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Chapter 1 - Chapter 1=Adaptaion by Natural Selection...

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