How did the government of ancient Athens differ from that of the early Romans?

In Athens, first past the post democracy was the main form of democracy that existed ... Probably influenced by Greek culture, Rome's republic had an aspect of democracy in which all Roman citizens voted to elect Senators to positions of power in the Senate. Citizenship, however, was a different story.

Athenian democracy: Institution that began around the 5th century BCE, and was limited to the city of Athens and its periphery.

The Roman Republic: Began in 509 BCE, and was governed by representative officials.