In the biological world, an open system is one in which materials and energy are transferred between organisms and the exterior environment. In an open system, there is some type of boundary that allows energy or materials to cross over for the purpose of growth and change.
In nature, all living things are considered open systems, as they continually exchange energy and matter with their surroundings and at times reach a point of balance. Living organisms are constantly modifying in reaction to the environment and therefore are considered open systems.
In contrast, a closed system is one in which no material enters or exits. A closed system is independent of the environment, and it reaches a point of equilibrium more easily.