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Overview: This case study in the form of a set of PowerPoint slides examines the evolution of light fur in beach mice from the molecular level up to the population genetics level. Author/Source: Evo-Ed Grade level: 13-16 Time: one to two class periods Teaching tips: This series of slides provides direct links to studies and data sets and integrates active learning strategies such as clicker questions, minute papers, and think/pair/share. Students could review the website or ppt slides before class and clicker questions/application questions could be source of class discussion. Concepts: Correspondence to the Next Generation Science Standards is indicated in parentheses after each relevant concept. See our conceptual framework for details. Natural selection and genetic drift act on the variation that exists in a population. Natural selection acts on phenotype as an expression of genotype. Phenotype is a product of both genotype and the organism’s interactions with the environment. Variation of a character within a population may be discrete or continuous. Continuous characters are generally influenced by many different genes. New heritable traits can result from mutations. Mutation is a random process. Organisms cannot intentionally produce adaptive mutations in response to environmental influences. Complex structures may be produced incrementally by the accumulation of smaller advantageous mutations. Inherited characteristics affect the likelihood of an organism's survival and reproduction. Over time, the proportion of individuals with advantageous characteristics may increase (and the proportion with disadvantageous characteristics may decrease) due to their likelihood of surviving and reproducing. Traits that confer an advantage may persist in the population and are called adaptations. The number of offspring that survive to reproduce successfully is limited by environmental factors. Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental.

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