This Study Guide on Contemporary Problems, Number 8, is one of a series prepared by the American Association for the Advancement of Science representing part of the 1974-75 National Science Foundation Chautauqua-Type Short Courses for College Teachers Program. This is a test edition and contains evaluation forms to be completed by the users and to be used in possible revision. Thorough discussions of several mathematical models are presented along with computer programs in BASIC to solve the related problems. This is followed by self-study problems and solutions. The contents include: population models--deterministic and discrete, deterministic and continuous, and stochastic; a predator-prey model; an economic model; and modeling in probability. (MP)