This catalog contains lesson descriptions of the available biology lessons on PLATO IV, compiled to assist instructors in planning their curricula. Information is provided for 87 lessons in the following areas: introductory material on experimental tools and techniques; chemical basis of life; cellular structure and function; reproduction and development; molecular genetics; biogenetics; classical genetics and genetics of populations; evolution; population biology and ecology; plant anatomy and physiology; plant pathology; taxonomy; human anatomy and physiology; and animal behavior. For each lesson, the following are provided: file name, author, instructional objective, description, student time, grade level, subject area, and special notes. (MH)