Which of the following is NOT a key component of ecosystem structure?

The correct answer is climate change because it is not a structural component of an ecosystem. Ecosystem structure refers to the organization and arrangement of biological and physical components within an environment. This includes trophic levels, which represent the feeding relationships among organisms; species diversity, which indicates the variety of species present within an ecosystem; and habitat, which defines the physical environment where these species live and interact.

While climate change can significantly affect ecosystems by altering conditions and potentially impacting species and habitats, it does not constitute a structural component in itself. Structure is concerned with the existing elements of an ecosystem at a given time, whereas climate change pertains to external factors that influence the functioning and dynamics of those ecosystems over time.