We need information about what Mendel did. We have no way of knowing what he did without the information you were given and did not include here.
Osmosis is the net movement of water across a semi-permeable membrane from an area of lower gradient concentration to an area of higher gradient concentration. On the other hand, tonicity is the ability of an extracellular fluid to make water move into or out of a cell through osmosis. A solution's tonicity is related to its osmolarity or the total concentration of the solutes in a solution.
When solutions of varying osmolarities are separated through a membrane that is permeable to water but not to solute, water from the side with lower osmolarity will move to the area with higher osmolarity.
Hydrophilic
A phospholipid is comprised of a phosphate hydrophilic head, which means that it is "water-loving," and a fatty acid hydrophobic tail, which is "water-hating." The head and the tail are joined together by a glycerol molecule.
The phosphate head is attracted to water because it is charged (i.e. negatively). Water is a polar molecule, which means that there is an uneven distribution of charges within its molecular structure with the oxygen side being "more negative" than the rest of the atom (which is "more positive" near the hydrogen). Thus, the negatively-charged nature of the phosphate head and the parts of the water molecule which are positively charged enable the two to form an "attraction" towards one another.
On the other hand, the hydrophobic tail is nonpolar, which means that it does not have a "more positive" or "more negative" side or part in its molecular structure. These differences in structure with water make the hydrophobic tail unattracted to water molecules and more attracted to other uncharged, nonpolar molecules (such as fats and oils).