Essayist: Earth is a living organism, composed of other organisms much as animals are composed of cells, not merely a thing upon which creatures live  This hypothesis is supported by the fact that, like all organisms, Earth can be said to have a metabolism and to regulate its temperature, humidity, and other characteristics, divorced from the influences of its surroundings
Of course, Earth does not literally breathe, but neither do insects (they have no lungs), though they respire successfully
an example of a type of organism whose status, like Earth's, is unclear