Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.

By the end of this section, you will be able to do the following:

Name and describe the distinguishing features of the three main groups of mammals
Describe the likely line of evolutionary descent that produced mammals
List some derived features that may have arisen in response to mammals’ need for constant, high-level metabolism
Identify the major clades of eutherian mammals

In this video segment adapted from NOVA, animations of an asteroid hitting Earth are used to illustrate this widely accepted theory of dinosaur extinction and the resulting conditions that favored mammals.