What is an example of a conceptual model used to explain bodily functions to upper elementary students?

Using a balloon as a conceptual model to explain bodily functions is effective because it provides a tangible representation of how various systems operate. For example, inflating and deflating a balloon can be used to illustrate how lungs function during breathing. As the balloon inflates, it mimics the process of inhalation when air fills the lungs; conversely, when the balloon deflates, it represents exhalation. This visual and kinesthetic demonstration helps upper elementary students grasp abstract ideas about respiratory functions in a concrete way.

In contrast, while the other concepts listed are indeed useful models for teaching different scientific principles, they don't directly relate to bodily functions as effectively as the balloon does. Gravity and its effects focus on forces and motion, the water cycle pertains to environmental processes, and photosynthesis addresses plant biology. Each of these concepts has its own significance but does not provide the same direct analogy to bodily functions that a balloon does when discussing processes like breathing.