The Interactions of Food, Prey, and Predators in Outbreaks
Jensen and Ball (1970) experimented with about as simple an interaction between an organism, its food, and its predator, as it is possible to get — populations of bacteria and their protozoan predators maintained in culture flasks of water. They obtained the organisms from natural populations in a Michigan river, and added nothing but a sterile nutrient solution to the cultures. The bacteria grew on the nutrient solution and the protozoa ate the bacteria. By adding the same amount of this nutrient solution to flasks once every 7 days, they generated weekly peaks of great abundance of bacteria followed by peaks of protozoa. After each peak the numbers of both organisms remained at very low levels until the next injection of food. This manipulation had generated a classic feedback alternation of a cyclic prey and its predator. However, when they added exactly the same amount of nutrient solution each week, but in equal daily amounts, these regular peaks and troughs of bacteria and protozoa failed to appear. The numbers of both organisms continued to fluctuate, but instead at much lower amplitudes, and at random to each other and in time. A clear demonstration of the dependence of both organisms on their food supply.
KeywordsNutrient Solution Thought Experiment Poor Site Rabbit Population Relative Shortage
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