Evolution E-2 Study Guide PDF

**I. Key Concepts in Evolutionary Processes** **1. Evolution:** **Phenotype- observable characteristics of an organism** - **Definition:** A change in allele frequencies in a population over time. - **Microevolution:** Small-scale changes within a species or population....

**I. Key Concepts in Evolutionary Processes** **1. Evolution:** **Phenotype- observable characteristics of an organism** - **Definition:** A change in allele frequencies in a population over time. - **Microevolution:** Small-scale changes within a species or population. - **Macroevolution:** Large-scale changes that result in the formation of new species or taxonomic groups. **2. Four Forces of Evolution:** - **Mutation:** Introduction of new alleles (can be beneficial, deleterious, or neutral). - **Gene Flow (Migration):** Movement of alleles between populations due to migration. - **Genetic Drift:** Random changes in allele frequencies, especially significant in small populations. - **Natural Selection:** The only evolutionary process that consistently increases adaptation. It favors traits that enhance survival and reproduction. **II. Natural Selection and Fitness** **1. Natural Selection:** - A process where certain phenotypes increase reproductive success, leading to changes in allele frequencies. - **Directional Selection:** Favors one extreme phenotype, causing allele frequencies to shift in one direction (e.g., antibiotic resistance). - **Stabilizing Selection:** Favors intermediate phenotypes and reduces genetic diversity (e.g., optimal birth weight). - **Disruptive Selection:** Favors extreme phenotypes at both ends, potentially leading to speciation (e.g., beak size in seedcrackers). - **Balancing Selection:** Maintains genetic diversity by favoring heterozygotes or rare alleles (e.g., heterozygote advantage in sickle-cell anemia). **2. Fitness:** - **Absolute Fitness:** The total number of offspring an individual contributes to the next generation. - **Relative Fitness (w):** The fitness of a genotype compared to the population average. - If relative fitness w\>1w \> 1w\>1, the allele increases in frequency. - If w=1w = 1w=1, the allele changes randomly. - If w\