My boyfriend says plants and trees have natural lifespans like animals. I say if a plant doesn’t die of disease, drought, famine, fire, etc., it will not die. Look at those age-old trees out in California. Please help us settle this argument. –S.U., Chicago
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Death, disease, drought, famine–at last a question that speaks to me. To simplify matters, let’s just talk about trees. One may speak of trees having life spans, in the sense of having an average life expectancy. The Encyclopaedia Britannica, furthermore, notes that the “lifespans of trees, like those of all organisms, are limited.” But while this is certainly true–no tree is immortal–it is also deceptive. Trees may have life spans, but they don’t have fixed life spans, as animals do. It is reasonably certain that no human, no matter how coddled, would survive past some definite point–say, 120 years. But this cannot confidently be said of trees.
Trees endure as long as they do basically because they’re nonhierarchical organisms. In animals, all vital functions are controlled by the central nervous system, the guiding element of which is the brain. When the brain dies, so does the animal. By contrast, vital functions in trees are decentralized. A large part of the tree can die, and indeed routinely does die, without killing off the tree as a whole. Most of a mature tree is dead except for a few layers under the bark.
You may well be crazy, Georgia, but if so you’re in good company. Many great minds of science have also ruminated on this vital issue. They were less concerned with how close, though, than with how period, since landing upside down is no mean feat. The leading theory for years was that the flies did a half barrel roll sideways a la the Blue Angels just before landing. This idea was shot down in 1958 when Natural History magazine published photos showing that in fact flies do a sort of backward somersault. On approaching the ceiling, and while still flying right side up, flies extend their forelegs over their heads till they can grab a landing spot with the suction cups in their feet. Their momentum then enables them to swing their hind legs up, like a gymnast on a trapeze. Result: inverted fly, home and dry. So the answer to your query is, they get real close. Hope that’ll do.
