Why energy in most ecosystems must flow from the sun then to autotrophs and finally to heterotrophs in that order.?

Energy in most ecosystems flows from the sun to autotrophs and then to heterotrophs due to the foundational role of autotrophs in converting solar energy into chemical energy through photosynthesis. Autotrophs, such as plants, capture sunlight and produce organic compounds, which serve as the primary energy source for heterotrophs, like animals and decomposers. This hierarchical flow ensures that energy is efficiently transferred and utilized, with each trophic level relying on the previous one for sustenance. Without this order, the energy needed to sustain life in ecosystems would be disrupted.