Homework # 4, WFC 10 2007 NAME: Gary Rossetto 1. The reading by Krebs (Chapter 5) includes two examples with lakes, one in which fertilization from sewage was regarded as bad and one were deliberate fertilization was regarded as good. What do these examples have to do with ecological communities (hint: what is the chapter title?). Why is one good and one bad? In Lake Washington, the pollution was due to sewage. The nutrients in the sewage increased the growth of certain species but not others. After the pollution stopped the unbalance was corrected, and the algae and crustacean populations returned to their original levels. In the Great Central Lake, the fertilizer was added on purpose. The added nitrogen increased all levels of organisms proportionally, so there was never an imbalance. 2. In lecture, Dr Moyle discussed how the realized niche of an animal is determined in part by its interactions with predators and competitors, which is how it fits into a community. Provide an example of a species that has narrower niche as a result of
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