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The Allobiosphere
| Article
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16043 |
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Section : |
NATURAL SCIENCE
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| Issue
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7 / 1989 |
1,583 Words |
| Author
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John S. Edwards
John S. Edwards is professor of zoology at the University of
Washington, Seattle. He does research in neurobiology and has
a long-standing interest in the literature of exploration. |
All flesh is grass. That fundamental and simple truth reminds us that all animals--predators, parasites, and herbivores alike--ultimately depend on the plant world, on the capacity of green plants to trap solar energy from that great nuclear reactor at the center of our solar system and to convert it to the chemical energy we recognize as food. To be precise, we should now substitute most for all animals, for there are some newly discovered exceptions to the time-honored generalization. Exploration of the sea floor in places where hot springs well up from deep in the earth's mantle has revealed a number of animals, new to science and dwellers in perpetual darkness, that have achieved independence from green plants and thus from the gifts of trapped sunshine. These bizarre animals depend on bacteria that can harness the energy of chemicals from the deep hot springs, the hydrothermal vents lying along the margins of the great plates that make up the crust of our restless earth.
But these animals--the hydrothermal prawns and clams, for example--are the rare exceptions to the rule, and the ecologist looking at the flow of energy and of nutrients through the living world justifiably concentrates on the vast majority of animals for which photosynthesis by green plants is the source of energy and food. It is not surprising then that the parts of the earth that receive the most sunshine, tropical lowlands and estuaries, should also be the most productive of plants and animals. Sunshine alone, of course, is not the only requirement for abundant life. There must be water and nutrients too, and these three factors together govern the distribution of life on earth. So it is in those desert, high mountain, and polar regions where plant life is excluded that animal life is rare or
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