Why did the paramecium die of dehydration when the water solute was raised all the way up AND lowered all the way down? Why did the paramecium die of dehydration when the water solute was raised all the way up AND lowered all the way down?

There is a certain water potential maintained in the body of the paramecium, which can change in response to changes in its environment. When the water solute level is increased all the way up, the water potential in the surrounding is a lot lower than the water potential inside the paramecium. Due to this steep water potential gradient, water will leave the paramecium's cell into the surrounding via osmosis. Water being transported out of the paramecium will cause it to dehydrate and die.

In the opposite case where the solute level is lowered all the way down, no water will enter the paramecium cell because its water potential is lower than the surroundings. The difference in water potentials is so great that the water entering the paramecium's cell will cause to burst and die.

Note: remember that diffusion and osmosis takes place down the concentration gradient. The concentration of one environment is determined in reference to another.

Hope that answers the question, have a great day!