Answer:
The Utility of Trophic Levels
The trophic level concept has been exceptionally durable: it has been one of the basic concepts of ecology for six decades and is one of the few ecological concepts contained in the vocabulary of most educated people. The reason for this distinguished place in the scheme of things is that the concept is both simple and useful. Furthermore, it is universal: it applies to all ecosystems.
Because of this universality, trophic levels enable us to compare the role of vastly different species in vastly different systems. For instance, we can discuss and understand a lake and the surrounding forest with a common language: the forest has its vegetation and its leaf litter; the lake has its phytoplankton and its dissolved organic matter (basal species). The forest has herbivorous insects, birds, and mammals; the lake has zoo-plankton (herbivores). And so on. We can use the same language to compare these two systems with any other ecosystem anywhere in the world.
