Final answer:
The Sun's energy comes from nuclear fusion, where hydrogen atoms merge to form helium in the Sun's core, releasing energy we see as sunlight. This sunlight is then used by plants and other photosynthetic organisms to create energy-rich compounds through photosynthesis, supporting life on Earth.
Step-by-step explanation:
The source of energy for the Sun is nuclear fusion. In the Sun's core, hydrogen atoms combine under extreme pressure and temperature to form helium, releasing an immense amount of energy in the process. This energy is what we observe as sunlight and is harnessed by photosynthesis on Earth by plants, algae, and cyanobacteria to create chemical energy in the form of glucose.
Through photosynthesis, these producers are able to convert solar energy into a form that can be used by themselves and ultimately by other organisms along the food chain. As energy is not recycled, it is continuously needed to be captured by producers and then gets passed through the ecosystem as various organisms consume one another.
Moreover, the energy from the Sun is so abundant that it exceeds the world's energy needs by almost 10,000 times every day. Humans have learned to harness this energy in several ways, including burning wood, coal, and petroleum, which are all stores of ancient sunlight energy captured through photosynthesis millions of years ago.