The first edition of BIOLOGY, written by Dr. Rob Brooker, Dr. Eric Widmaier, Dr. Linda Graham, and Dr. Peter Stiling, has reached thousands of students and provided them with an outstanding view of the biological world. Now, the second edition has gotten even better! The author team is dedicated to producing the most engaging and current text that is available for undergraduate students who are majoring in biology. We want our students to be inspired by the field of biology and become critical thinkers. To this end, we have made the following changes throughout the entire book. Each chapter in the second edition begins with an interesting story or set of observations that will catch the students' interests as they begin to read a chapter. To help students test their knowledge and critical thinking skills, we have increased the number of Concept Check questions that are associated with the figure legends and revised the many of the questions at the end of each chapter so they are at a higher level in Bloom's taxonomy. An answer key for the questions is now provided in an appendix at the end of the book. To further help students appreciate the scientific process, the Feature Investigation in each chapter now includes three new elements: a Conclusion, the original journal citation for the experiment, and questions that are directly related to the experiment. Many photographs and micrographs have been enlarged or replaced with better images. The presentation of the material has been refined by dividing some of the chapters into smaller sections and by the editing of complex sentences. With regard to the scientific content in the textbook, the author team has worked with hundreds of faculty reviewers to refine the first edition and to update the content so that our students are exposed to the most cutting edge material.