The process of equalizing ion concentration by movement of fluid through a semipermeable membrane is known as a. nerve impulse transmission. b. osmosis. c. osteoporosis. d. diuresis.

The answer is b-osmosis

B. osmosis
the definition of osmosis - molecules of fluid passing through a semipermeable membrane from a less concentrated solution into a more concentrated one.  This equalizes the concentrations on each side of the membrane.

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle