Unlike Prokaryotic cells, eukaryotic cells can actually have different roles instead of the same cell over and over. This, obviously, leads to more complex creatures. Basically, a theory (now proven correct) called The Big Gulp explains how we took in small prokaryotic organisms to do the roles for us. For example, mitochondria makes proteins so we do not have to waste our own organisms protein.
Dolphins sleep with one eye open
Communication among scientists in different countries would be nearly impossible because they would not know for certainty which organism was being discussed if each country had its own name for an organism.
The answer should be genes.
