Name ______Class ______Date ______

Introduction to Ecology

Use this activity to familiarize yourself with the virtual Ecology lab bench and its simulations.

Ecology is the study of interactions among organisms and between organisms and their physical environment. The Virtual Bio Lab allows you to simulate and analyze some of these interactions, from predator-prey cycles to competition to population crashes caused by human impacts.

Enter the Virtual Bio Lab and select the title of this activity from the “Biomes & Populations” menu on the whiteboard. You will be taken to the virtual Ecology lab bench.

The Ecology Lab Bench Controls

At the top left of the Ecology lab bench screen, you will find the Species Selector, which allows you to choose species for simulations and experiments. At the Ecology bench, the list of featured species is limited to those whose interactions with each other and the environment are relatively well known. Selecting a species and clicking the “Add” button will cause that species’ name to appear in the Species Tracking box. The Abiotic Variables panel to the right of the Species Tracking box allows you to select different biomes and adjust abiotic factors in the ecological simulation.

The Controller, which is a console found in the lower middle of the screen, allows you to run ecological simulations. Clicking the green play button begins the simulation. A simulation offers a glimpse of the ecological interactions involving the selected species and biome over time. Results, such as changes in population and biomass, will appear in graphical form to the right of the Controller. The speed of the simulation can be accelerated or slowed by clicking the “+” and “-” buttons. The simulation can also be paused at any time by clicking on the red pause button. If left to run on its own, and if virtual populations do not grow beyond a certain number (in the trillions), the simulation will run for 50 virtual years.

Part A: Getting Results

Like the other lab benches, the virtual Ecology lab environment features a clipboard of presets. In this case, choosing a preset will set up a specific simulation including the species, initial populations, abiotic factors, and biome.

Click on the preset clipboard and select the preset called “Exponential Growth.” Three species will appear in Species Tracking, each with an initial population of 1000. As you can see in the Abiotic Variables panel, the selected biome is temperate deciduous forest. Note that in Species Tracking, the “Excess Food” box is checked for each species. This means that the simulation assumes that food scarcity is not a limiting factor for these populations.

Click the green play button to start the simulation. Data will appear on the right side of the screen. You can click on the buttons at the top of the data window to see how species change in terms of population, biomass, and energy. Note that the view of the biome changes as the simulation runs, and specific days’ weather conditions are revealed in a small window below the graphs. Click the “+” sign on the Controller to speed up the simulation to intervals of 1 year. Typically, the simulation will run for up to 50 years, but it will stop earlier if any of the populations reaches a number in the trillions. You can pause and continue the simulation at any time.

1. Using the population view of the graphs, describe the patterns of population growth of the three species.

2. What might account for the slight, temporary plateaus or dips in the curves of all three species?

On the Controller, click the “Time” button, which will restore the initial preset settings. In Species Tracking, click on Elk and then click “Edit Species.” The “Edit Species” menu allows you to see the life history parameters that control how a species behaves in a simulation. “Average Offspring per Birth,” for example, reveals how many offspring an adult female elk will give birth to, on average, each year.

Above that, the birth interval determines how often, in days, the species reproduces. For example, “364” means adult females give birth every 364 days, or once a year. This may also be set to specific days of the year, for organisms whose reproduction varies by season. If set by days, “120 and 240” would mean the species gives birth on the 120th and 240th days of the year.

“Age to Adult” is the age, in days, of an elk that is mature enough to reproduce. Species that have a relatively old age of maturity tend to have slower population growth rates than species that mature at young ages.

To learn about the other parameters and how they affect the ecology simulations, you can click on “Help” in the lower left of the main lab window.

3. In the table below, record the information that determines the elk’s reproductive rate. Do the same for the other two species you are tracking.

Data Table 1
Species / Birth interval (in days) or specific birthing days / Avg. offspring per birth / Age to adult (in days)
Elk
House mouse
Snowshoe hare

Note the two buttons at the bottom of Species Tracking: “Catastrophe” and “+/-Population.” You can click on these at any time when a simulation is running. When you click either button, the selected species, which you can choose using the pull-down menus next to the buttons, will immediately experience a sudden change in population. The “+/- Population” button can simulate a sudden increase in population, due to events such as immigration or human-induced habitat restoration, or a sudden decrease, due to something like hunting or emigration. “Catastrophe” will only reduce population. For either effect, you can adjust the population by a percentage, or you can delete the % symbol so that the adjustment will be a specific number of individuals. Note: Once a population has crashed all the way to zero, you cannot replenish it if “+/- Population” is set to a percentage. You must delete the % symbol and instead use an integer, such as “+50.”

4. Review your answer to Question 1, or rerun the simulation. Given the data you recorded in Data Table 1, why are there different population growth patterns among these three species?

Part B: Analyzing Data

Go back to the preset clipboard and click on “Nutrient Level.” This will set up a population of Kentucky bluegrass in a temperate deciduous forest. Look at the settings, including the initial grass population and abiotic variables.

5. What is the initial population of the grass, and what is the nutrient level?

On the Controller, click the play button to start the simulation of the grass living in this particular biome under the given conditions. Let it run until 10 years have passed. Use the acceleration button to advance time at a faster rate, such as five-year intervals. Use the pause button to pause the simulation. Above the graphs, click “Save” to save the results to the Lab Book.

The red Lab Book can be found lying on top of the Controller. Click on it to open the book. The data will be saved by default under the name of the biome, but the title can be edited. Click on the title and change it to “Low Nutrients” to note the conditions the grass grew under during the simulation. Both in the Lab Book and in the main window, you can switch between three different graphs: population, biomass, and energy. On the biomass and energy graphs, “t” stands for metric tons, and “MJ” stands for megajoules. In the Lab Book, you can also click on “Show Data” to see the raw data. Close the Lab Book to return to the Ecology bench.

6. Toggle between the three graphs to analyze what happened to the grass over the course of ten years. What was the grass population after ten years? Its Biomass? Energy? Record the data in Data Table 2 on the next page.

7. Reset “Time,” adjust the nutrient level to “Medium,” and run the simulation again for 10 years. Save the data, edit the title to note the nutrient conditions, and fill in the second row of the data table. Then, repeat the simulation again to show growth under high nutrient levels.

Data Table 2
Nutrient Level / Grass population after 10 years / Grass biomass after 10 years (t) / Grass energy after 10 years (MJ)
Low
Medium
High

7. How did changing the nutrient level in the biome affect the growth rates of the grass?

8. Assuming there is limited space in the biome, why would higher nutrient levels allow for more biomass but not greater numbers of individuals?

Part C: Saving Results

As with the other lab benches, you can save your Lab Book data as a lab book file (.lbk) that can be emailed to your teacher or reviewed later on. To do this, open the Lab Book, click on the “File” menu, and select “Save File.” A window will appear that asks you where you want to save the file and how to name it.

Once you save a file, you or someone else can then open the file in the Virtual Bio Lab by going to the same menu in the Lab Book and selecting “Open File.” You will be prompted to select the file from somewhere on your local drive. When opened, the results you saved will appear in the Lab Book.

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Virtual Bio Lab 1 Biomes & Populations

Introduction to Ecology