A food chain is a path for the transfer of matter and energy through an ecosystem by eating being eaten. It represents a linear sequence of organisms in which each organism consumes the one below it and is, in turn, consumed by the one above it. It depicts the flow of energy and nutrients from producers (autotrophs) to consumers (heterotrophs) and decomposers. Each trophic level, or feeding level, in a food chain represents a decrease in energy and biomass as some energy is lost as heat during energy transfer between organisms.