What does the term "ecosystem" refer to?

The term "ecosystem" refers specifically to a community of living organisms and their physical environment, interacting as a system. This means it encompasses not only the various species, such as plants, animals, and microorganisms, but also their non-living surroundings, which include elements like air, water, soil, and climate. This interaction between the biotic (living) and abiotic (non-living) components forms a complex web of relationships essential for the survival and growth of the organisms involved.

In this context, while the other options touch on aspects related to ecosystems, they do not capture the full breadth of what an ecosystem is. A collection of different species in a habitat refers more narrowly to biodiversity rather than the interactions and relationships within an ecosystem. The physical features of a region pertain more to geography rather than to living organisms and their interactions. Lastly, a network of food chains is an important component of ecosystems, but it doesn't encompass the entire scope of the ecosystem, which includes many more interactions beyond just feeding relationships.