The tabs at the top of the screen allow you to access the Introduction, Notebook, Assignments, Glossary, and Help. These tabs will lead you to information and tools that are outside the applet itself.

Introduction: This provides an overview and links to background information on the lab.

Notebook: Record your own notes on the results of the lab--your hypotheses, details about results, and conclusions. You can also move data from the Results pages directly to the Notebook - see Exporting.

Assignments: Doing the assignments is critical to understanding the concepts of this lab. The Assignments here were written to benefit a wide range of general biology classes and you should find them helpful, but check with your instructor before proceeding with any Assignments.

Glossary: The glossary contains definitions for selected terms in the lab.

Help: Explanations and hints on using all features of the lab are in Help.




Input buttons allow you to change variable information that enables you to make comparisons between many different hypothetical population situations. Clicking on any of the input buttons on the left-hand panel will bring up the controls for that variable. The controls for all of the variables appear as a parameter slider bar at the bottom of the screen. For slider bar controls, double-click on a slider to directly enter a value or click and drag the green diamond on the slider bar to the desired value.


The different parameters in PopEcoLab are changed by using these controls to adjust the variable for each parameter. Ideally, you want to compare different values for each parameter. The parameter adjustments are described below:

Initial Population: The initial population for brown sparrows is set at 200 birds while the default value for blue sparrows and hawks is zero. Population size of each species can be manipulated by clicking and dragging the slider bar.

Clutch Size: Clutch size is the number of eggs that a female bird lays in her nest. The default value for brown sparrows and blue sparrows is three eggs while the default clutch size for hawks is two eggs. Controlling clutch size is one way to influence the rate of reproduction for all three species of birds.

Life Span: Brown and blue sparrows have a shorter life span than hawks. Notice that the default life span for sparrows is one year while the life span for hawks is three years. This feature allows you to manipulate mortality rates (independent of predation) to influence life span.

Flight Speed: The ability of sparrows to avoid predation by hawks depends on their flight speed. The default value for both brown and blue sparrows is 6 meters per second (m/sec).

Competition: Although brown sparrows primarily eat seeds and blue sparrows primarily eat insects, the two sparrows are potential competitors because brown sparrows can also eat insects and blue sparrows can also eat seeds. The relative rates of consumption of these "alternative resources" can be varied independently.

Resource Densities: Seed density and insect density directly influence the carrying capacity of brown and blue sparrows, respectively. The default values are 100 seeds per meter-squared (m2) and 100 insects/m2.

When you have finished selecting all of your desired parameters, click Done to indicate that you have finished changing inputs. You can now use the small pull-down menu at the bottom left corner of the screen to choose how many generations to run the experiment on (100-500), and then click Run Experiment to run an experiment.



Results are given automatically after the Run button is clicked and an experiment is completed. The results are presented in various forms which can be accessed by clicking on the appropriate button in the frame on the left side of the page:

Population Size: The population size is represented as a plot of the number of birds in the population versus the number of year of the experiment. Note that you can user your cursor to drag on the graph to zoom into an area. Click on the graph once to zoom back out.

Phase Space: Phase space is shown as a plot of the number of one species (e.g., blue sparrows) against another (e.g., brown sparrows) as population numbers change over time. This type of plot is valuable for examining relationships between species. You can select the species for each axis by using the pull-down menus below the plot. Note that you can user your cursor to drag on the graph to zoom into an area. Click on the graph once to zoom back out.

Textual Data: Text columns of raw data for population size of brown sparrows, blue sparrows, and hawks are available for your reference.

Input Summary: A summary table of the input parameters for the experiment that you carried out is available for your reference.



As you run experiments, form hypotheses, and test them, you should keep notes on your hypotheses and findings in the PopEcoLab Notebook.

Main Window: The main section of the Notebook is an editable text box to which you can add and modify text at any time. The contents of the Notebook are not saved between uses of Lab; therefore, it is suggested that you "Export" and print or save the Notebook contents if you would like a permanent record of your work.

Control Buttons: You will see a row of control buttons at the bottom of the notebook window. These include Export, and Undo Editing.

Export Notes:The current contents of the notebook are exported to a temporary HTML file. This file is then opened in your browser. Exporting your notes allows you to print them when you are done with your assignment.

NOTE: extremely long notes will cause machines to hang when trying to export. If you are running many experiments it is best to print your notes and clear the notebook occasionally.

Undo Editing: Any changes you have made to the notebook since it was last opened will be removed, restore it to its state when it was opened.