The principle that explains how energy moves through an ecosystem is the energy flow concept. This concept is illustrated by the food chain, where producers (like plants) convert sunlight into energy through photosynthesis. This energy is then passed on to consumers (herbivores and carnivores) and eventually decomposers, which break down organic matter. The 10% rule is significant, as it indicates that only about 10% of the energy at one trophic level is transferred to the next. As a result, energy decreases as it moves up the food chain, affecting ecosystem dynamics and species populations.