The smallest group among the options provided is a population.
Here's a brief breakdown of the terms:
- Population: A group of individuals of the same species living in a specific area.
- Community: A group of different populations (species) that live together in a defined area.
- Ecosystem: A biological community (community) of interacting organisms and their physical environment.
- Biome: A large geographic biotic unit, a major community of plants and animals with similar life forms and environmental conditions.
Thus, in terms of size: population < community < ecosystem < biome.