population

Doesn't just have to apply to people, though. Everything has a population of nodes. A beach has a population of crabs, or of grains of sand for that matter.

Population is a term used to describe a group of individuals of the same species that live in the same place at the same time. In terms of evolution, a population is the smallest unit that can evolve. For this reason, populations are often reffered to as the units of evolution.

An entire species does not have to change for evolution to occur. One population of that species may evolve differently than another, the study of which is called population genetics.

Pop`u*la"tion (?), n. [L. populatio: cf. F. population.]

1.

The act or process of populating; multiplication of inhabitants.

2.

The whole number of people, or inhabitants, in a country, or portion of a country; as, a population of ten millions.

© Webster 1913.