Final answer:
Osmosis is the movement of water through a selectively permeable membrane from an area of higher water concentration to an area of lower concentration, facilitated by aquaporins, and crucial for cellular homeostasis. Option 1 is correct.
Step-by-step explanation:
The movement of water molecules down its concentration gradient and across selectively permeable membrane is known as osmosis. This process involves water moving from an area of high water concentration to an area of lower water concentration. Osmosis is crucial for maintaining cellular homeostasis and is facilitated by proteins called aquaporins. For instance, if a cell is in a hypertonic solution, water will move out of the cell to reach equilibrium, and vice versa for a hypotonic solution.
It's also important to note that osmosis is different from other transport mechanisms like diffusion, which transports materials across membranes, or pinocytosis and phagocytosis, which involve the cell's uptake of liquid and large particles respectively. Osmosis specifically refers to the transport of water across a semi-permeable membrane.