I don't know at all im lost
When the concentration o molecules inside a cell is different form the concentration of molecules outside a cell, we can either call it hypertonic or a hypotonic solution, and the difference between the two concentrations is called a concentration gradient.
Hypertonic - name given to a solution that has a bigger concentration than the concentration in a cell.
Hypotonic - name give nto a solution that has a smaller concentration than the concentration in a cell.
Hope it helped,
BioTeacher101
Perhaps the answer is "physical characteristics". I am simply making an educated guess, however I do know early philosophers classified organisms into two groups, Plants and Animals, and identified them based on physical characteristics.
