11Human EcologyThe history of human populationsAn ecological puzzle: The recent growthof the human populationTesting alternative solutions to the puzzleExam average = 80Final exam will incorporate some questions based on exams 1-32Another test of the possible role of predators in controlling herbivoresOak tree, herbivorouscaterpillar and predatory blue jay3Spray = oak tree leaves sprayed with insecticide.Control = leaves left unsprayed and open to birds and insects.Cage = leaves caged so that birds were excludedbut not herbivorous insects.426. The data above support which of the following hypotheses?Oaks are not eaten as much as one would think because …a.Predators remove many herbivores from ecosystemsc. Both predator pressure and plant defenses contribute to a reduction in herbivore consumption of oak leaves
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