Thousands of farms are located along the mississippi river and its tributaries through the central u. s. as water washes into the river after a heavy rain, it brings with it nutrients from fertilizers added to farmland. these materials flow downriver and eventually enter the gulf of mexico, where they create conditions for a dead zone — a region of the ecosystem that can’t support any living creatures. this is an example of a tragedy of the commons. why is the dead zone seasonal?

The return of the wolf to yellowstone national park will probably affect the bird population to some degree, not significantly. while wolves will hunt birds when necessary, they prefer to hunt larger prey. the bird population will most likely only be affected when hunting is scarce for the wolves. birds of prey will also probably not be affected as much as other birds who spend more time on the ground hunting for food as the tend to spend more time in the air or in trees since they do not need to stay on the ground for long due to the nature of the way they hunt.

Control variable- changedependant variable- stays the samechanging- food itemsdependant- presences of proteins