The biological basis for assigning all human beings into a singe species is that there so many, even tons of living organisms living on earth. These organisms differ in their external and internal organs and so to differentiate them from them, they are being classified into kingdoms then classes then phylums then family.
<span>The reason behind the lipids which are able to function as protective barriers in cells is that lipids do not dissolve in water.
If lipids dissolve in water, they will not be able to function as protective barriers in cells. N</span><span>ucleic acids, proteins, lipids and carbohydrates are the four types of macro-molecules in the cell.</span>
