I think it is because it's easier to "control". Like the books usually said that the nucleus is the control center of the nucleus, so if the nucleus located at the center or near center of the cell. So like easy contact, easy control, easy communication etc.
Salinity is the concentration of dissolved salts in water. Density is the degree of compactness in a substance. By determining the salinity of a substance, you would also be determining the density.
B. alternating phosphate groups and pentose residues
The axial skeleton provides support and protection for the brain :)
During amount of great temperature change like hot to cold.\
