What is an ecosystem?

An ecosystem is defined as a community of living organisms interacting with their environment. This includes not only the organisms themselves, such as plants, animals, fungi, and microorganisms, but also the physical components of their surroundings, like air, water, soil, and climate. The interactions within this community—such as predation, competition, symbiosis, and nutrient cycling—help to create a complex and dynamic system where energy flows and matter cycles.

This answer encompasses the essentials of an ecosystem, as it highlights both the biological aspect (the living organisms) and the physical environment that they exist in. The balance and relationships among these components play a critical role in sustaining life and maintaining the health of the ecosystem.

The other options do not provide a complete understanding of an ecosystem. While a collection of species can be part of an ecosystem, it does not include interactions or the environmental context. Similarly, defining an ecosystem solely as a specific habitat type overlooks the dynamic relationships between organisms and their environments. A group of populations is more related to the concept of a community, which is just one aspect of an ecosystem.