What is osmosis: And why does it occur

What is osmosis and why does it occur? Osmosis is the movement of water molecules from an area of high water concentration to an area of low water concentration through a partially/selectively permeable membrane (PPM). What are the differences and similarities between osmosis , active transport and diffusion? Osmosis is a term used to describe the movement of water molecules from a high water potential to a low water potential. Osmosis is the diffusion of water molecules, down the concentration gradient, through a partially permeable membrane. The water moves fro the area of high concentration of water to low concentration water. Active transport is the movement of solutes from an area of low concentration to high concentratio so against the concentration gradient. In summary, the loop of Henle is surrounded by tissue fluid which has a high concentration of ions in it. This causes water to move out of the descending limb by osmosis . This produces a more concentrated filtrate because of this, ions move out of the loop in the thin ascending limb.