What were the similarities and what were the differences between Ancient Greek republics and the Ancient Roman Republic?

There are many differences and similarities between these two institutions. Firstly people living in both Republics had quite a strong patriotism for democracy and freedom. They believed in freedom of speech and rights of the plebs well that is what the aristocracy was suposed to believe. However there are some differences. for one the Romans had two consuls sort of like two prime ministers but with executive authority the idea being that one could restrain the other to prevent Dictatorship. The Roman republic had these people caled "Tribunes" whose job it was to defend the rights and interests of the Plebs, they could veto any Senatorial decision. In times of strife and emergency the Romans could elect a "dictator" for 6 months. None of the above list you would find in the Greek system.