The presence of predators, such as grey wolves, is required to keep the elk population in check. If the population of elk is allowed to grow unchecked, the vegetation would eventually start disappearing, followed by the disappearance of the elk.
Elk obviously need the vegetation they eat to be abundant and unlike believed in the past they need to be prayed on by predators. Without predators, the elk overpopulate and eat all of the plants and cause other animals like beavers to die off.
The respiratory system works directly with the circulatory system to provide oxygen to the body. Oxygen taken in from the respiratory system moves into blood vessels that then circulate oxygen-rich blood to tissues and cells.
