General:
* People
* Inhabitants
* Residents
* Citizens
* Community (if referring to a specific group)
* Nation (if referring to the entire country)
* Society
More Specific:
* Census (referring to a numerical count)
* Demographics (referring to statistical data)
* Humanity (referring to all humans)
* Man (archaic, often considered outdated)
* Folk (informal, often used for a specific group)
Related to Biology:
* Species
* Colony
* Population size
* Population density
* Biota (all living organisms in a region)
The best synonym to use depends on the specific context and the nuance you want to convey.