Question

Explain why energy in most ecosystems must flow from the sun, then to autotrophs and finally to heterotrophs, in that order.
short paragraph

Answer 1

Nearly all ecosystems depend on sunlight because it is the primary source of usable energy; autotrophs (producers) capture that solar energy and convert it into chemical energy through photosynthesis (or chemosynthesis in a few systems), building the organic molecules that form biomass. Heterotrophs (consumers) cannot fix energy from sunlight, so they must eat autotrophs or other consumers to obtain that chemical energy. Energy transfer between trophic levels is inefficient—much is lost as heat—so energy flows in one direction (sun → producers → consumers) and must be continuously supplied by the sun rather than recycled.