Many changes and revisions have been made throughout this new edition, some major, some small. The chapters on life history (embryology), locomotion (energetics, burrowing, respiration),and circulatory system have been substantially revised. Many revised figures not only incorporate newer information but also present an evolutionary summary within a cladistic context. Several new Box Essays have been added, e.g., snakes and their prey (\`Borrowed Toxins,\` Chapter 6), and prosthetic \`cheetahs\` (\`On a Fast Track,\` Chapter 10). Over Turning Chordates. New developmental genetics now indicate that chordate ancestors flipped over immediately, reversing dorsal and ventral surfaces. That inversion remains the basis of the chordate body plan today. Amphioxus Basal. Recently completed genomic studies reveal that amphioxus is not the sister group to vertebrates; urochordates now occupy that position. Amphioxus is the most basal living group of chordates, but this enlarges its importance as a possible model for the first chordates. Evo-Devo. The genomic section on evolution and development (Chapter 5), introduced in the last edition, is expanded here by including more examples throughout the chapters of how master control genes (Hox genes) build vertebrate systems and provide the genetic basis for major evolutionary changes. This helps to inform and enlighten traditional form, function, and evolution of vertebrates with modern genetic mechanisms. Phylogenetic Relationships. Thanks again to evermore comprehensive molecular comparisons of vertebrate groups, phylogenetic relationships are becoming better resolved, and natural groups are emerging from this analysis with better clarity. This is the basis for revisions in the third chapter, but these are carried forward throughout the book. To purchase an eBook version of this title, visit www.CourseSmart.com (0077346009). With the CourseSmart eTextbook version of this title, students can save money, reduce their impact on the environment, and access powerful web tools for learning. Faculty can also review and compare the full text online without having to wait for a print desk copy. New figures are used, along with new text, to show modern tools of the trade, insights from new fossils, dinosaur respiration, and cardiovascular shunting. Cross references direct students to other areas of the text where they can refresh their understanding or clarify an unfamiliar subject. Important literature is cited at the end of each chapter, and Web links connect them to further references and resources. A glossary of definitions is included at the end of the book with appendices covering vector algebra, International System of Units, common Greek and Latin combining forms, and classification of the chordates. The use of color has been expanded, which brightens these sections of the book. But color has also been used to better correlate and compare structures between figures in these chapters.