Light. Please see details.?

without sunlight, plants can't grow. without plants, the oxygen balance of the atmosphere is altered dramatically, and all of the herbivores that rely on plants for survival will die. carnivores that ate the herbivores will no longer have their regular food source, and will either eat each other or starve. either way, the only things that are completely unaffected by light are creatures in the very deep ocean, or those that live far underground.