### Biota--A Predator-Prey Simulation.

The discipline of population ecology involves laboratory and field observations that require long periods of time and sophisticated materials. Because of these constraints, students typically do not generate experimental data when introduced to this important field. As a result, for many of these students, the concepts driving population ecology are often abstract and vague. The computer simulation Biota allows students to generate and study population data in a quick and easy fashion.

Biota is a simulation tool for studying the processes which influence the sizes of plant and animal populations. The simulation consists of a set of mathematical equations that model various population interactions, and a set of generic tools that allow the user to define both the organisms that will interact in a simulation and the geographical area in which those species will interact.

In a typical use of Biota, you first define a set of species. As shown in Figure 1, this involves setting various parameters required in the mathematical models (population growth parameters, modes of migration, etc.). Next, you characterize the types of interactions between species (predator, prey, competitor or independent) and the strengths of those interactions (coefficients of interaction). Finally, you define the type and number of geographical areas in which the species will interact. After populating the regions with organisms, the resulting "biota" is allowed to cycle. Using a variety of data viewing tools (bar charts showing absolute popu-lation number, species time series, phase plots, etc.), the resulting species population levels are analyzed. In this way, features governing population levels can be studied and explored.

#### Figure 1. editing a species interaction parameters.

Figure 2 shows the general simulation summary window from a Biota simulation where two species (foxes and rabbits) are interacting within and migrating among nine distinct geographical regions. In the upper left area of the window, you see that a bar chart displaying absolute popu-lation numbers for each species has been inset in each of the nine regions. The lower portion of the window shows the actual population data for each species in each region during each iteration.

#### Figure 2 results from simulation in 3x3 region using Biota.

One of Biota's strengths is its ability to allow different mathematical models to apply simultaneously to different population interactions. Thus, species A may be a predator to species B (modelled using the Lotka/Volterra with Carrying Capacity equation), but may be a host to the (parasite) species C (modelled using the Nicholson & Baily equation). In this way, complex scenarios involving multiple interaction types can be modelled and studied.

Biota has been released in a §-format along with sample data sets and a user manual. The program is currently limited in the number of interaction models and data analysis tools available, but future enhancements will include more sophisticated models (such as Leslie, Gilpin and lag incorpor-ation), enhancement of data analysis options, and the ability to set traps in order to investigate sampling effects.

Clearly, Biota will be a powerful demonstrative tool for exploring population ecology. However, its high level of sophistication and generalizability will also allow it be used in research settings. With these features, we feel Biota truly embodies the 3Ps of Project BioQUEST, and will proudly take its place among the other fine BioQUEST modules. For the last three years BioQUEST has been developing a demonstration prototype showing how the BioQUEST philosophy, the field of biology and computers could all come together. Now BioQUEST is beginning testing, refining and fleshing out these materials to create a project suitable for distribution and use. BioQUEST is currently negotiating with Addison-Wesley Publishing Company, Inc. about publishing the BioQUEST Collection. During the 1990-1991 academic year field tests on the BioQUEST materials will be conducted. We hope to have BioQUEST material commercially available by Jan 1992. At that time BioQUEST will consist of software, manuals and additional text which discuss some new approaches to and ideas for biology education.

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