One of the standards for life science addressed in the "Next Generation Science Standards" (NGSS Lead States 2013) is "Ecosystems: Interactions, Energy, and Dynamics" (HS-LS2). A critical concept included in this core idea is biodiversity. To show competency, students are expected to design investigations, collect data, and perform mathematical analyses to explain how biodiversity changes or remains the same in ecosystems with different factors (Figure 1, p. 26). To this end, this article describes an ecosystem biodiversity investigation, posing the research question: How do two wooded areas of different ages compare in species biodiversity? Students collected plants in two areas of a local wooded ecosystem and calculated Simpson's biodiversity index (Figure 2, p. 26) to compare the relative abundance of organisms in each area. Simpson's biodiversity index gauges the number of species present and the relative abundance of each species. The Simpson index, named for Edward H. Simpson, a British statistician, was chosen because it can compare data sets of unequal size and is based in probability, and research has demonstrated that students using it better comprehend relative abundance of species, or species evenness (Dor-Haim, Amir, and Dodick 2011). As the focus in science education shifts to integrating authentic scientific practices with content learning, so must teaching. The biodiversity lesson described here can help achieve that goal.