Final answer:
In a hypotonic solution, water enters a red blood cell due to osmosis and may cause the cell to swell and burst, a process called hemolysis.
Step-by-step explanation:
If a red blood cell is soaked in a solution of lower than normal salt concentration, a hypotonic solution, water will enter the cell due to osmosis. Because the concentration of solutes inside the red blood cell is higher than in the surrounding solution, water rushes in to dilute these solutes. Without homeostasis to regulate this influx, the red blood cell may swell and eventually burst, a process known as hemolysis. Unlike in hypertonic solutions where the cell would shrink due to water leaving the cell, in a hypotonic environment, the excessive intake of water can damage and destroy the red blood cell.