What defines an ecosystem?

An ecosystem is defined as a dynamic and complex network that encompasses both living organisms and their physical environments. Therefore, the correct option articulates that an ecosystem comprises a biological community, which includes all the living organisms (plants, animals, microorganisms), in conjunction with the physical (such as soil, water, and air) and chemical factors (like nutrients and pH levels) that influence the survival and interactions of these organisms.

This holistic approach highlights the interconnectedness of biotic and abiotic components in maintaining the balance and health of the ecosystem. For example, plants rely on sunlight, water, and soil nutrients to grow, while animals might depend on these plants for food. The physical environment also affects how organisms interact and thrive within their habitats.

In contrast, other options fail to capture the comprehensive nature of an ecosystem. Focusing solely on physical components or just the interactions among living organisms neglects vital aspects that contribute to ecosystem functionality, such as the role of nutrients and energy flow. Similarly, defining an ecosystem only in terms of a community of plant species ignores the critical interactions and relationships with various other organisms that are essential for ecosystem processes. Therefore, the selection accurately reflects the definition and complexity of ecosystems as studied in sustainability and ecological sciences.