Why are the four spheres of earth called open systems?

The four spheres of Earth—atmosphere, hydrosphere, lithosphere, and biOSphere—are called open systems because they exchange matter and energy with each other and with their surroundings. For instance, water vapor from the hydrosphere can enter the atmosphere, while gases from the atmosphere can dissolve in water bodies. This continuous interaction allows for processes like weathering, erosion, and biological activity, underscoring the interconnectedness of these spheres. Such exchanges are essential for maintaining the balance and dynamics of Earth's environment.