Ecology

Challenge 1 "The Producers":

Step 1:

Try to get two plants to happily co–exist. In any given ecosystem, most organisms will carve out a niche for themselves where they can obtain all of the necessities to survive. Often, different species within the ecosystem will compete for the resources that a niche provides. However, certain species live well together—symbiotically, parasitically, or by staying out of each other's way. For example, lichen and moss, often the primary colonizers of a new ecosystem, tend to live fairly harmoniously in each other's vicinity. Let's see what happens in this model.

Imagine the ecosystem is newly forming—the previous ecosystem has been destroyed by fire or flood—and the first colonizers of the successive ecosystem are, of course, producers. Given the two fictitious species of plants in the simulator, predict what will happen in this young system and record your prediction in the Data Table. Then run the simulator to 100 time steps and record the population numbers for both plants. Answer the following:

1. What assumptions does this model make about co-dominance as well as the general terrain of the ecosystem?
2. Do you find one producer to be dominant? Why might one producer be dominant over another?

Step 2:

Now you'll introduce an herbivore into the environment. In theory, an herbivore native to the ecosystem should feed primarily on the dominant species. In this system, the herbivore may consume enough of the dominant species to give the non-dominant species a chance for proliferation and survival. Click on herbivore A (the rabbit) and choose "eats plant A." Predict and record what will happen to the population numbers in the ecosystem. Then, run the simulator and record your results. Answer the following:

1. Does adding the herbivore establish a more equal field? Is one producer still dominant over the other? Why might one producer be dominant over another?
2. If the simulation included decomposers, how would your current results change?
3. How do producer population numbers with the presence of an herbivore compare to the primary colonizer model?

Conclusion:

When the ecosystem contains plants only, one species of plant out-competes the other(s) and takes over. This illustrates the "competitive exclusion principle," which theorizes that no two species can occupy the same niche at the same time in a particular locale if resources are limited. (You can read more about this in the Unit 4 text.) The presence of a consumer is needed to keep that plant in check and allow the other species to survive.

The primary colonizers of an ecosystem, the producers, are also the harbingers of primary succession. As these pioneer plants die and decay, they add organic material to the soil, which, over time, will allow for secondary succession—generally larger and more delicate producers such as trees.

From what you have learned in the text and videos, how are humans contributing to the creation of a vastly rapid form of succession? In other words, how are we speeding up the effects of the competitive exclusion principle and thereby altering the outcome of that ecosystem's natural succession?

Challenge 2 "Food Web"

Now that you have a sense for the interrelationships between the trophic levels, see how big you can make your food web and still have all of the species you add survive through the end of the simulation run. Keeping the ideas of succession and the competitive exclusion principle in mind, think of the many factors that may go into sustaining an ecosystem. Is there any way we can all get along and live side by side?

Step 1:

First you'll run a less than "real-life" scenario. Choose only one organism from each trophic level and make sure that the food chain goes in a straight line from one trophic level to the next, i.e., Herbivore A eats Plant A, Omnivore A eats Herbivore A, and the Top Predator eats Omnivore A. Let Plant B survive on its own and see what happens. Predict whether each species will survive, and whether it will increase or decrease in number, as well as whether Plant B will survive to the end. Record your prediction in the Data Table and then run the simulation twice and record your data. Use X for "die out," ↑ for "increase in numbers," and ↓ for "decrease in numbers." Answer the following:

1. Was your prediction correct? How did you arrive at your prediction? What differences were there between your prediction and the simulation?
2. What would happen to this imaginary ecosystem if the producers were to die out?
3. Did any of the species increase in number? What could account for this increase? Which species decreased in number and what might account for this decrease?
4. Which populations would benefit the most from the presence of decomposes?

Step 2:

Now try a more "real-life" scenario and experiment with what might happen in an ecosystem that is more like a web. This time click the "all on" button. The model shows who eats whom and the paths by which energy is transferred. Predict which populations will die out, increase in numbers, or decrease in numbers and record your predictions. Run the simulation twice and record the results in your Data Table. Then try to modify who eats whom in order to ensure the survival of all species and record what was changed in your chart. Finally, answer the following:

1. Was your prediction correct? How did you arrive at your prediction? What differences were there between your prediction and the simulation?
2. Were you able to modify the parameters so that each species survived? Explain how you decided what changes to make.
3. Which way does energy flow and how does eating an organism result in energy transfer?

Conclusion:

Ecosystems have an extremely complex web of cause and effect. Changing one connection or altering the population of any species within an ecosystem can have dire, cascading effects on all others within that ecosystem.

Consider the following:

1. How does a natural ecosystem offer suggestions toward a more economical and eco-friendly human model?
2. How do humans affect the greater food web? In this model, how could humans who do not live in the ecosystem still manage to alter the flow of energy within the web?

Design your own Argument:

Getting Started:

The Ecology Lab simulation allows you to create different food chains and webs within a model ecosystem. Once you establish the food chains and webs in the model ecosystem, you can run the simulation to determine the effect on the population of each organism. To answer the guiding question, you will need to design and conduct several experiments using the online simulation. To accomplish this task, you must determine what type of data you will need to collect during each experiment, how you will collect it, and how you will analyze it.

To determine what type of data you will need to collect, think about the following questions:

• What will serve as your dependent variable (population size, number of different populations, relative abundance, and so on)?

• What type of data will you need to keep a record of during your investigation?

To determine how you will collect your data, think about the following questions:

• What will serve as a control (or comparison) condition during each experiment?

• What types of treatment conditions will you need to set up for each experiment?

• What variables will you need to control during each experiment?

• How often will you collect data and when will you do it?

• How will you keep track of the data you collect and how will you organize the data? To determine how you will analyze your data, think about the following questions:

• How will you determine if there is a difference between the conditions during each experiment?

• What type of calculations will you need to make?

• What type of table or graph could you create to help make sense of your data?

Argument:

Once your group has finished collecting and analyzing your data, prepare a whiteboard that you can use to share your initial argument. Your whiteboard should include all the information shown in the figure below.

Argument on Whiteboard:

Share your Argument:

To share your argument with others, we will be using a round-robin format. This means that one member of your group will stay at your lab station to share your group’s argument while the other members of your group go to the other lab stations one at a time to listen to and critique the arguments developed by your classmates. The goal of the argumentation session is not to convince others that your argument is the best one; rather, the goal is to identify errors or instances of faulty reasoning in the arguments so these mistakes can be fixed. You will therefore need to evaluate the content of the claim, the quality of the evidence used to support the claim, and the strength of the justification of the evidence included in each argument that you see. In order to critique an argument, you will need more information than what is included on the whiteboard.

You might, therefore, need to ask the presenter one or more follow-up questions such as:

• How did you use the simulation to collect your data?

• What did you do to analyze your data? Why did you decide to do it that way? Did you check your calculations?

• Is that the only way to interpret the results of your analysis? How do you know that your interpretation of your analysis is appropriate?

• Why did your group decide to present your evidence in that manner?

• What other claims did your group discuss before you decided on that one? Why did your group abandon those alternative ideas?

• How confident are you that your claim is valid? What could you do to increase your confidence?

Once the argumentation session is complete, you will have a chance to meet with your group and revise your original argument. Your group might need to gather more data or design a way to test one or more alternative claims as part of this process. Remember, your goal at this stage of the investigation is to develop the most valid or acceptable answer to the research question!

Report:

Once you have completed your research, you will need to prepare an investigation report that consists of three sections that provide answers to the following questions:

1. What question were you trying to answer and why?

2. What did you do during your investigation and why did you conduct your investigation in this way?

3. What is your argument?

Your report should answer these questions in two pages or less. This report must be typed, and any diagrams, figures, or tables should be embedded into the document. Be sure to write in a persuasive style; you are trying to convince others that your claim is acceptable or valid!

Ecology Simulator