This text bridges the gap between introductory physics and its application to the life sciences. It is intended for advanced undergraduates and beginning graduate students. The Fourth Edition is updated to include new findings, discussion of stochastic processes and expanded coverage of anatomy and biology. The text includes many problems to test the student's understanding, and chapters include useful bibliographies for further reading. Its minimal prerequisites and wide coverage make it ideal for self-study. The fourth edition is updated throughout to reflect new developments.