This Click & Learn is the third resource in Lab 5: Community and Ecosystem Ecology. It has students explore examples of how changes in the population numbers of one species can affect species at other trophic levels and ultimately the entire ecosystem.
To use this resource as part of Lab 5, assign each of the four case studies in the Click & Learn to small groups of students. Each group should work together to present the information from their case study and address discussion questions of your choice. Examples of discussion questions are shown below.
General
Define the term “trophic cascade.”
Arctic Tundra Case Study
- What is the effect of foxes on seabirds? Why?
- What effect do seabirds have on soil nutrients? Why?
- What effect do soil nutrients have on grass? Why?
- Describe the picture at the end of the case study that illustrates the result of adding foxes to an arctic tundra ecosystem, and explain this result.
African Savanna Case Study
- What is the effect of the rinderpest virus on the wildebeest population? Why?
- What is the effect of vegetation on the frequency and intensity of fires? Why?
- Describe the graph at the end of the case study that illustrates the effect of eradicating rinderpest through a vaccination program. Explain why this would be the result of eliminating the virus.
Midwestern Lake Case Study
- What is the effect of bass on minnows? Why?
- What is the effect of phytoplankton (photosynthetic microorganisms) on carbon influx — that is, removing carbon dioxide (CO2) from the atmosphere? Why?
- What effect does the bass have on the amount of carbon stored in the lake? Why?
Venezuelan Jungle Case Study
- What effect do predators, such as jaguars, have on vegetation? Why?
- What effect would the disappearance of predators have on the structure of the forest?
- What effect would the decline of herbivores have on the ecosystem?