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We are using Apologia’s Elementary Zoology Book 3 for science this year. It is the study of land animals. We just finished chapter 4 and completed an interesting demonstration of the relationship between populations of predator and prey, specifically the cougar vs deer population.
The experiment called for marking off a 2 ft X 2 ft square on the floor. In that square, begin by placing 3 “deer” (2 X 2 inch paper- we printed a picture of a deer on ours). Then, a cougar (a 6 X 3 in cardboard) was tossed into the square. The cougar has to “eat” 3 deer to survive to the next generation. If the cougar survives, then the next generation toss 2 cougars. If the cougar doesn’t survive, use 1 cougar for the next generation. (The assumption being that another cougar will move into the territory) For each deer that doesn’t get eaten, add 1 additional deer to the next generation.
For our experiment, we had several generations where our cougar failed to eat any deer. That made the deer population increase dramatically. The instructions only said to make 20 deer. We wound up needing over 90 deer at one point in our experiment.
We graphed our results in Excel. I was impressed at how well the graph demonstrates the predator/prey population relationship. First, the population of the prey begins to increase, this allows the predator population to increase. As the predator population increases, more prey will get eaten. Eventually, the predator population will fall too because there is not enough prey.