ECOLOGY AND THE ENVIRONMENT
Estes and Palmisano (1974), Estes et al. (1998) – Questions for Discussion
- Define a “keystone species”. (1pt)
- Explain how the orca-otter-urchin-kelp food web presented in these studies is an example of top-down control. (1pt)
- Define “anthropogenic”. What anthropogenic effect is most responsible for the situation with the sea otters? (1pt)
- Find and describe another example of a keystone predator creating top-down controls in an ecosystem. Include the predator species, the ecosystem, and how the ecosystem would be different in the absence of the predator species. (2pt)
- Estes and Palmisano 1974, Figure 1: What is this graph comparing? Why is there no line shown for vegetation at Shemya Island (hint: what does “coincident with the ordinate” mean)? (2pt)
- Estes and Palmisano 1974, Figure 2: Based on this graph, describe the difference in sea urchin size demographics between the two islands. Why are these differences important? (2pt)
- Why are kelp forests ecologically important? What ecosystem services do they provide to other species living in the region? What benefits can they provide to human societies? (3pt)
- Keystone species are often the focus of conservation efforts. Describe at least one benefit of this approach to conservation, as well as one potential risk or limitation to this approach. (3pt)
- Describe a potential strategy for bringing these kelp forest ecosystems back into balance. What might be a limitation or difficulty with implementing this strategy? (3pt)
- Write out the citations for both papers using Ecology formatting. (2pts)
–> Please read the two short articles to answer the questions, Also please read the other attached document to follow the formatting.
Answer preview
In their graph, Estes & Palmisano (1974) evaluate how to vegetation cover and sea urchin density changes with changes in the depth of the ocean. The graph indicates that the percentage of vegetation cover decreases with an increase in depth. Similarly, the sea Urchin density in Shemya Island increases with the proliferation of the vegetation cover. On the other hand, the sea Urchin density in Amchitka decreases with an increase of the vegetation cover and fall in depth. In Shemya Island, the vegetation line is not shown because it coincides with the ordinate line. Both ordinate and vegetation lines share the same variables.
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ECOLOGY AND THE ENVIRONMENT
