Ch. 9 Reading Notes Summary: Generalities about predator-prey systems are elusive, but ecological knowledge indicates that extermination of any element in a community is unwise. The coexistence of prey and predators for centuries indicates that, given proper food and cover, natural prey populations can withstand predation and that predator populations can survive low prey densities. The effect of predators on prey populations in nature may depend on the complexity of the community in which they live. In the absence of predators and hunting, many prey populations overpopulate their ranges and ultimately decline rapidly from starvation and disease. In complex communities that have abundant food and cover and several species of predators and prey, predators moderate the occurrence of drastic peaks and troughs in prey populations. Ecological evidence from relatively simple natural communities, however, indicates that predators may depress declining prey populations to very low levels and maintain those levels for extended periods of time. In such
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