Energy use and production is a huge cycle that happens on Earth every day! It’s pretty cool. The sun shines onto the Earth, and plants use that sun to create energy and grow, a process called photosynthesis… Species that turn the sun’s light energy into food are called primary producers. Things that eat primary producers are called primary consumers, like grasshoppers and other herbivores. Secondary consumers eat primary consumers, like an eagle, and tertiary consumers eat secondary consumers. These are called trophic levels, and it’s how energy is passed though different plants and animals. Only about 10% of energy is passed on to each trophic level, which is pretty inefficient.

Try growing plants with different levels of sunlight. Since the energy in animals' food comes from plants (since you know what happens if you starve), you can prove that this energy comes from the sun by proving that plants with too little sunlight won't grow.

By the way, it's any kind of light that plants can use to grow. If you were running electric lights on power from a nuclear power plant, you could grow plants, eat them, and get the energy from them, and the energy would be from the nuclear fission in the power plant, not the sun.