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Predator and Prey

Predator-prey relationships (that is, neither competitive nor mutualistic relationships) have been seen as providing the necessary stability for almost infinite numbers of species to exist in ecosystems. Such relationships do so by keeping the size of species populations in check at supportable levels.

Stefano Allesina and Si Tang, researchers at the University of Chicago, have studied such relationships. Their recent investigations have noted that, "When prey are high, predators increase and reduce the number of prey by predation. When predators are low, prey decrease and thus reduce the number of predators by starvation. These predator/prey relationships thereby promote stability in ecosystems and enable them to maintain large numbers of species.

By contrast, mutualistic relationships may reinforce the growth of large populations and competitive relationships may depress population numbers to the point of ecological instability."

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