1. Multiple population groups: This is the most direct opposite, meaning more than one group of people.
2. Diverse population: This emphasizes the presence of many different groups with varying characteristics, such as ethnicity, culture, or socioeconomic status.
3. Heterogeneous population: This describes a population composed of dissimilar individuals or elements. It's similar to "diverse population" but emphasizes individual differences rather than group differences.
4. Intermingled population: This implies that different population groups are mixed together and interact with each other.
5. The whole population: This refers to the entirety of individuals within a particular region or context, regardless of any specific group affiliation.
The most appropriate opposite depends on the specific context and what you are trying to highlight.