This document contains an instructional unit which deals with one major topic in ecology. It focuses on the variables which affect the development of populations and determine their final size within a given period of time. The variables operating in nature which determine the development of populations are numerous, thus complicating the task of scientists who attempt to evaluate the separate influence of each variable. To help overcome some of these problems this unit attempts to study the development of animal populations using a computer simulation. This instructional method presents a relatively simple simulation of the complex realities of animal populations. The booklet was designed to guide the student through the content being addressed and introduce the student to the computer simulation. It also includes additional activities, questions, and summaries. (TW)