The Online Biology Book was created by Dr. Michael J. Farabee of Estrella Mountain Community College in Arizona. The textbook represents Farabee's many years of teaching freshman biology and offers "introductory hypertext learning modules for a wide variety of biological topics." It is organized into 41 chapters (and a glossary), all of which are revised and updated frequently. Topics include chemistry, cellular biology, genetics, thermodynamics, protein synthesis, plants and structure, animal organ systems (integumentary, respiratory, etc.), evolutionary theory, and biological diversity, among others. Each chapter is well illustrated with color images and supported by hyperlinked glossary terms. Whether seeking an introduction to or a review of general biology, this well-maintained site is worth the visit.