Light energy from the sun flows into an ecosystem and is transformed into other forms through organisms.
Producers occupy trophic level 1: they capture sunlight and transform it into chemical energy by photosynthesis.
The transformed energy is then available for consumers at higher trophic levels: primary consumer, secondary consumer, etc.
Most energy is lost at each trophic level; only about 10% is available to the next level on the trophic pyramid.
After organisms die, the remaining energy is available to decomposers, which recycle nutrients in the ecosystem.