Lesson 4: Competition Between Populations Preview CT-STEM

Invaders

In this activity you will examine the effects of a competitor species on a population. The competitor species in this case is called invaders. The invaders eat grass, just like the bugs. The invaders do not eat bugs, and the bugs do not eat invaders.

Set the initial number of birds to zero and the grassland region to 100%.
Press SETUP and then press GO/STOP. As the model is running, press the LAUNCH AN INVASION button on one side, sometime between a time of 100 and 500 .
Run the model until it pauses on its own.
Record your observations below.

Questions

Please answer the questions below.

Question 4.1

Describe what happens in the model when you first add invaders to the ecosystem. Specifically, describe the effect on the bug population.

Question 4.2

Estimate the carrying capacity of the bugs when invaders are present.

Question 4.3

Try to find at least two different parameters to change that will result in the bug population dying out. Don't add predators or change the initial number of bugs. Briefly describe the approaches you used.

Question 4.4

Based on your understanding of resource availability and carrying capacity, why do you think invaders influence the bug population? How is this scenario similar to or different from the previous activity?

Question 4.5

Compare the total carrying capacity of the bugs and invaders in the left ecosystem to the carrying capacity of bugs in the right ecosystem. What do you notice about these values? Why do you think this is the case?

Notes

These notes will appear on every page in this lesson so feel free to put anything here you'd like to keep track of.