Sunlight radiating heat, visible light, and ultraviolet light is the source of almost all life on Earth. Everything you see alive around you is there because a plant somewhere was able to capture sunlight and store it. All animals live from these plants, whether directly (as with herbivores) or indirectly (as with carnivores, which eat the herbivores). This is true of mammals, insects, birds, amphibians, reptiles, and bacteria … everything living. Every life-form on the surface of this planet is here because a plant was able to gather sunlight and store it, and something else was able to eat that plant and take that sunlight energy in to power its body.