In this Biodiversity Counts activity, students learn how scientists calculate a biodiversity index using a page from the phone book as their data source. The printable five-page PDF handout includes a series of inquiry-based questions to get students thinking about what they already know about biodiversity and how living and non-living things are connected, step-by-step directions for calculating a biodiversity index, and a worksheet that includes brainstorming questions and areas for recording answers.