read the two articles and answer the questions below :
- What evidence is there that sea otters are a keystone species?
- Explain how the killer whale-sea otter-urchin food web is an example of top-down control.
- Explain the difference between Figure 2a and 2b from Estes and Palmisano (1974).
- What are the benefits of large-scale/long-term approaches in ecological research?
- Write out the citation for these journal articles using the format of the journal Ecology.