What caused osmosis?

Answer 1

Osmosis is the passive diffusion of water across a partially permeable (or semipermeable) membrane with a net transport from a region of high water potential to a region of low water potential.

High water potential means there is a relatively low concentration of solutes (a low solute potential), whereas low water potential has a higher concentration of solutes (also known as a high solute potential). The partially permeable membrane is selective to particles due to the small size of the pores in the membrane, which is not large enough to allow solutes to pass across it, but is large enough to allow water molecules to pass across.

The process is passive, meaning no energy input is required, as it is a result of the random movement of water molecules in solution. During osmosis, water molecules will move in both directions, but will equilibrate when the water potential on each side is equal, and as a result there will have been a net movement of water down a concentration gradient. At this equilibrium, water molecules will continue to travel across the membrane, but at an equal rate in each direction, so that no further net change occurs.