Textbook in PDF format Biology is a traditional, comprehensive introductory biology textbook with coverage from cell structure and function to the conservation of biodiversity and is appropriate for a one- or two-semester biology course. Biology focuses on three themes: systems, evolution, and the nature of science. These themes are integrated into all aspects of the textbook, from the unit learning outcomes to the theme-based feature readings in the text. Recognizing that instructors are increasingly being asked to engage their students while still providing them with a firm foundation in core biological principles, the authors of Biology integrated relevant content throughout the text to better allow students to make connections and think more scientifically