PAS Index

The Population Analysis System (PAS) consists of a series of microcomputer programs designed to help you construct models and analyze the dynamics of populations of organisms inhabiting variable environments. The picture above shows the opening screen of the PAS shell or organizer.

PAS FreeWare

PAS software is now distributed free-of-charge and can be downloaded by following the instructions below:

From Windows Explorer, create a folder called PAS on your hard drive (C: drive)

Download the PASzip.EXE file by clicking here.

In Windows Explorer, go to the PAS folder and locate the executable file PASzip.EXE

Double-click on PASzip.EXE.

The PAS programs and help files will be unzipped into the PAS folder. To run the programs in Windows, use Windows Explorer to locate the executable file PAS.EXE in the PAS folder and double click on it. An online User Manual containing a description of the PAS system and how it works (including tutorials) can be found below.

When publishing analyses done with PAS, please cite this web page and/or the book "Principles of population dynamics and their application" by A. A. Berryman (Stanley Thornes, Cheltenham, UK). Click here for more information.

PAS USER MANUAL

One-species Analysis

Pressing [2] in the PAS Main Menu will access programs for modeling and analysis of populations consisting of a single species. All other species are relegated to the environment of the subject population. The programs are:

P1a - Analyzes and models population census (time series) data.

P1b - Builds logistic population models and simulates dynamics.

Two-species Analysis

Pressing [3] in the PAS Main Menu will access programs for modeling and analysis of the interaction between two covarying populations such as predators and their prey, competitors or cooperators. The programs are:

P2a - Analyzes census data collected at equal time intervals on two coexisting species.
P2b - Models and simulates the dynamics of two interacting populations.

Applications

Pressing [4] in the PAS Main Menu will access programs that use models created by other PAS routines. They are mainly self-explanatory and no user manuals are provided. Clicking on the programs below show examples of them in action:

P1i - Interprets the biological meaning of model parameters in P1a or P1b.
P1s - Evaluates the sensitivity and stability of single-species models.
P2p - Forecasts future population densities and probabilities of outbreak or extinction.
P2m - Plays management games and tests harvesting or pest control strategies.

Lessons

Pressing [5] in the Main Menu will access programs for learning the theory of population dynamics and how it can be applied to real-life data. They are mainly self-explanatory and no user manuals are provided. Clicking on the programs below show examples of them in action:

PL1 - Exponential growth and the limits to growth.
PL2 - Predator-prey interactions in time and space.
PL3 - Competition between species.
PL4 - Interaction between plants and herbivores and pest management.
PL5 - Predator-prey cycles and pest management.

Games

Pressing [6] in the Main Menu will access programs for studying simple artificial life systems, like cellular automata. They are mainly self-explanatory and no user manuals are provided. Clicking on the programs below show examples of them in action:

PG1 - The Game of Life.
PG2 - Logistic growth of cellular automata.
PG3 - Predator-prey automata.

System

© 1987-1994 Ecological Systems Analysis, 921 West Main Street, Pullman WA 99163 USA. Protected by United States Copyright Law. Materials on this and associated pages cannot be reproduced without the written consent of Ecological Systems Analysis.