The predator-prey and herbivore-plant relationships help keep the balance in the ecosystem. These interactions regulate or control the population size by preventing a certain population to become excessively abundant. In predation, one organism attacks and consumes another one. The relationships between predators and prey play an important role in structuring ecological communities, with predators influencing the dynamics of their prey in ways that cascade through ecosystems to affect processes such as productivity, biodiversity, nutrient cycling, disease dynamics, carbon storage, and more. Predator and prey populations cycle through time, as predators decrease numbers of prey. Lack of food resources in turn decrease predator abundance, and the lack of predation pressure allow prey populations to rebound.Predation can have large effects on prey populations and on community structure. Predators can increase diversity in communities by preying on competitive dominant species or by reducing consumer pressure on foundation species. In addition, because both predator and prey are ectothermic, their energetic requirements will be tightly linked to environmental temperature. Increasing temperature should have a significant impact upon predator–prey interactions. Predators shape ecosystems by modifying the dynamics of their prey directly and indirectly. Directly, predators reduce the number of prey by consuming individual prey animals. Less prey translates into decreased impact on their community. An example of a predator-prey relationship is a fox and a rabbit. The fox hunts the rabbit and consumes it as food. Predator and prey species tend to have a cyclic relationship. As one species increases the other increases, which eventually causes the first species to decrease. As the prey population increases, there is more food for predators. So, after a slight lag, the predator population increases as well. As the number of predators increases, more prey are captured. As a result, the prey population starts to decrease. Too many predators and not enough prey leads to predators starving and dying because they can't find enough food. Too many prey and not enough predators leads to the spread of disease and depletion of resources for the prey species and others that live in their habitat.Predators keep the prey population under control. The prey species could achieve very high population densities and cause ecosystem instability in the absence of predators. Predators also help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species.