But the life forms are as much part of the structure of the Earth as any inanimate portion is. It is all an inseparable part of a whole. If any animal is isolated totally from other forms of life, then death by starvation will surely follow. If isolated from water, death by dehydration will follow even faster. If isolated from air, whether free or dissolved in water, death by asphyxiation will follow still faster. If isolated from the Sun, animals will survive for a time, but plants would die, and if all plants died, all animals would starve.

—ISAAC ASIMOV, “The Case against Man”