Predator-prey equations
The predator-prey equations is an ecological system. Two linked equations model the two species which depend on each other: One is the prey, which provides food for the other, the predator. Both prey and predator populations grow if conditions are right.  Alfred J. Lotka found these equations in 1925. Vito Volterra  found them, independently, in 1926. For this reason, the equations are also called Lotka-Volterra equations.