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)