Here's how it works:

* Photosynthesis: Plants and other photosynthetic organisms capture sunlight and convert it into chemical energy stored in the form of sugars. This process is the foundation of nearly all food webs.

* Food Chains: Animals eat plants, obtaining the stored energy from those plants. Predators then eat other animals, further transferring the energy.

* Decomposition: When organisms die, decomposers (like bacteria and fungi) break down their remains, releasing the energy back into the ecosystem for other organisms to use.

While there are some ecosystems that rely on other energy sources (like geothermal vents at the bottom of the ocean), the vast majority of ecosystems on Earth are powered by the sun.