Here's why:
* Collective noun: A noun that refers to a group of individuals or things considered as a single unit.
* Ecosystem: An ecosystem encompasses a community of living organisms (plants, animals, bacteria, etc.) in conjunction with their physical environment (air, water, soil). It's a complex system made up of many interconnected parts.
Even though an ecosystem is made up of individual organisms and components, we think of it as a whole, functioning unit.