Ultimately, the energy that powers every living thing on Earth begins with nuclear fusion. Life on Earth depends on the sun's light and warmth, which comes from the fusion of hydrogen atoms in the star's core. Without this power source, the Earth would be a barren wasteland.
Food webs in nature can be complex, but all of them trace the origin of food energy back to the sun. The sun's light feeds autotrophs, which are plants that generate carbohydrates from sunlight, carbon dioxide and water. Herbivores and omnivores eat these plants, and carnivores and other omnivores eat those creatures. In the end, decomposers feed on all dead matter, releasing nutrients back into the soil to feed the next generation of plants. This cycle would be impossible without the sun's energy.
The sun is also the primary source of energy on Earth. While solar power generates electricity directly from the sun, the convection currents that power wind farms and the water cycle that feeds hydroelectric power also depend on the sun's energy and warmth. Even fossil fuels, long considered the bane of the environment, derive their energy from the sun. Millions of years ago, plants and animals decomposed under the right conditions to produce coal, oil and natural gas, translating the sun's energy into a portable, powerful fuel source.