Write yоu аnswer tо pаrt (а) in the bоx below (be sure to also indicate which essay you are answering: 1, 2, 3, or 4). You must stick to the same question set (1, 2, 3, or 4) for each sub question you are answering. (6 Points) 1. Competition: (a) Describe the early experiments of Gause on two species of yeast (as mentioned in class and discussed in Krebs) and what do the results suggest about the competitive exclusion principle. 2. Predation: (a) List the four criteria that are required to determine whether a predator is limiting the distributions of its prey. If all of these criteria are not met, can you still claim that predators are limiting distributions of organisms? Why or why not (be specific, use real examples)? 3. Community Dynamics: (a) Define and contrast the terms “keystone species” and “dominant species”. 4. Temperature as a Limiting Factor: (a) “The stated purpose of the Endangered Species Act is to protect species and also the ecosystems upon which they depend." Why might listing polar bears as a Threatened Species under the Endangered Species Act have been problematic when it came to enforcing the necessary protection from this Act?