Smooth er has less things inside of it and rough is more complex.
The germ theory of disease states that many diseases are caused by microorganisms.
Gregor Mendel, in full Gregor Johann Mendel, original name (until 1843) Johann Mendel, (born July 22, 1822, Heinzendorf, Silesia, Austrian Empire [now Hynčice, Czech Republic]—died January 6, 1884, Brünn, Austria-Hungary [now Brno, Czech Republic]), botanist, teacher, and Augustinian prelate, the first person to lay the mathematical foundation of the science of genetics, in what came to be called Mendelism.