General terms:
* Population: A group of individuals of the *same* species living in the same area.
* Community: A group of *different* populations living in the same area and interacting with each other.
* Ecosystem: A community of organisms interacting with their physical environment.
More specific terms:
* Colony: A group of individuals of the *same* species living together in a close association.
* Herd: A group of large mammals, especially ungulates (like deer, elk, or cattle).
* Flock: A group of birds.
* School: A group of fish.
* Pack: A group of wolves or other wild canines.
* Pride: A group of lions.
* Troop: A group of monkeys or apes.
The specific term used depends on the type of organisms and the nature of their relationship.
