"What if…?" is a four-day summative assessment for a unit on biodiversity and evolution within a general biology course for ninth and tenth graders. Students gather evidence through multiple investigations to answer the questions: (1) "How has life changed on the planet? (2) What has caused those changes? and (3) What is happening to biodiversity now and into the future?" Students apply the crosscutting concept of cause and effect with an increased focus on their personal choices impacting the environment around them. They will logically anticipate plausible microevolutionary adaptations that are likely to be selected to improve species fitness in the future by one-million-year increments. These microevolutionary events, in turn, support speciation and macroevolution in intervals over one million years (Uyeda et al. 2011). The assessment is a series of situational questions that explores evolutionary inflection points throughout the history of life on Earth. Students analyze anthropomorphic trends, apply mechanisms of evolution, and accurately assign different anatomical, physiological, and behavioral adaptations to increase a species' fitness 15 million years into the future. Upon submission of the unit assessment, students will have demonstrated their understanding of the causes driving species evolution and the selection effects of inherited adaptations.