How is an ecosystem defined?

An ecosystem is defined as a community of interacting organisms and their environment, which encompasses both living (biotic) and non-living (abiotic) components. This definition highlights the relationships and interactions among various organisms, such as plants, animals, and microorganisms, as well as the physical environment they inhabit, including soil, water, and climate.

In an ecosystem, organisms interact with each other (e.g., predation, competition, symbiosis) and with their environment (e.g., nutrient cycling, energy flow). This interconnectedness is crucial for the stability and sustainability of the ecosystem, influencing factors like biodiversity and ecological health.

The other definitions do not capture the dynamic nature of ecosystems. For example, a group of unrelated species does not consider the critical interactions among them or with their environment. Similarly, a collection of extinct organisms lacks the vital aspect of ongoing interactions that occur between living organisms and their surroundings. Lastly, describing an ecosystem as an isolated habitat overlooks the connections that ecosystems have with surrounding areas, emphasizing that ecosystems are often part of larger biological networks. Therefore, the comprehensive nature of the correct answer captures the essence of how ecosystems function and thrive.