This is the student's text of one of the eight units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). The chapters include basic information about heredity, activities, and optional "excursions." A section on introductory notes to the student explains how to use the book. Data tables and empty spaces within the workbook format indicate where responses are expected. Illustrations accompany all instructions and the students are expected to select the proper equipment based on the illustrations. (SA)