they are caused by mutation. the best example of it are human blood groups.
The size of the algal size will increase or swell when a student removes an algal cell from its marine environment and puts it into a sample of freshwater.
Tonicity refers to the concentration of a solution compared to another solution. A solution is said to be hypertonic, if it has a greater concentration of solutes than the other solution. A solution is said to be hypotonic, if it has a lower concentration of solutes than the other solution. A solution is said to be isotonic, if it has the same concentration of solutes as of the other solution.
In a marine environment, the algal cells are said to be hypertonic with a higher concentration of the solutes than the freshwater. When such a cell is placed in freshwater with hypotonic environment, the concentration of solutes in the cell is higher than the external environment. In other words, it has lesser water molecules in it. As a result, osmosis occurs which is the movement of water molecules from a region of its higher concentration to a region of its lower concentration through a semipermeable membrane and water enters the cell from the freshwater. Thus, increasing the size of the algal cell or the algal cell swells.
