General:
* The population of the city is over 2 million people.
* The population density in this area is very high.
* The population of the world is increasing rapidly.
Specific:
* The population of pandas in the wild is dwindling.
* The population of bacteria in the gut can affect health.
* The population of students at this school is diverse.
Figurative:
* The population of my inbox is exploding.
* The population of ideas in her head was overflowing.
With prepositions:
* The population grew rapidly during the 19th century.
* The population of the city is spread out over a large area.
* The population is divided on this issue.