This book covers the basics of marine biology with a global approach using examples from many regions and ecosystems worldwide. This introductory, one-semester text is designed for non-majors. The authors have made a special effort to include solid basic science content needed in a general education course, including the fundamental principles of biology, the physical sciences and the scientific method. This science coverage is integrated with a stimulating, up-to-date overview of marine biology. - The fourth edition features two new chapters: The Microbial World and Multicellular Primary Producers: Seaweeds and Plants. - New and Unique "See It in Motion" video clips for each chapter are available via the Castro/Huber web site. These underwater clips feature video footage of marine animals and their behaviour. - Terminology has been changed to reflect the new classification system being used (3-domain system, seaweeds as protists).