Tracing food-web effects

Food webs contain multiple feeding relationships, so a change in one population can affect others indirectly. Top predators may influence herbivore abundance and therefore plant growth. These linked effects are sometimes called trophic cascades. In a simplified system, removing predators allows herbivores to increase, which increases grazing and reduces vegetation. Real systems may respond differently because alternative food sources, disease, and resource limits also matter. State the assumptions of a prediction.