The ecological principle that describes the flow of energy through a food chain is known as the trophic structure. This structure outlines how energy moves from producers to consumers at various levels. Producers, such as plants, absorb energy from the sun through photosynthesis and convert it into biomass. Primary consumers, or herbivores, feed on these plants, while secondary and tertiary consumers gain energy by eating other animals. Each step in the food chain represents a trophic level, with energy loss occurring at each level due to metabolic processes, reducing efficiency.