Summary of Chapter Concepts

Predators and herbivores can limit the abundance of populations. Using observations in nature and manipulative experiments, ecologists have found that predators commonly limit the abundance of prey and herbivores commonly limit the abundance of producers.

Populations of consumers and consumed populations fluctuate in regular cycles. Cycling populations have been observed frequently in nature and recreated in laboratory experiments. Lags in the response times of predator movement and reproduction linked to changes in the abundance of prey cause these cycles. Mathematical models have been developed to mimic the cycling behavior of predator and prey populations.

Predation and herbivory favor the evolution of defenses. Prey have evolved a wide variety of defenses including behavioral defenses, mechanical defenses, chemical defenses, crypsis, and mimicry. Producers have evolved defenses against herbivores including mechanical defenses, chemical defenses, and tolerance. Evolved defenses are commonly costly and can sometimes be countered by subsequent adaptations in predators.