When a cell is surrounded by a hypotonic solution, water moves into the cell. This happens because a hypotonic solution has a lower concentration of solutes compared to the inside of the cell. Water naturally moves from an area of low solute concentration to an area of high solute concentration through a process called osmosis.
In this case, since the external solution has fewer solutes, water will flow into the cell to balance the concentration on both sides of the cell membrane. This influx of water can cause the cell to swell and potentially burst if the cell wall is not strong enough to withstand the pressure.
Understanding this process is crucial in biology, especially when studying cell behavior in different environments. It explains why cells need to regulate their internal environment to maintain stability and function properly.