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  1. Earth

    Microbe polishes off pollutant

    Researchers have determined how long a pesticide residue would remain in the environment if the microbe Pseudomonas pavonaceae didn't metabolize it.

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  2. 19621

    This article raises the question of how oxygen levels have changed over the past 2 centuries, when carbon dioxide has been increasing. John MillsDecatur, Ala. There is a problem in this interesting article. The graph of oxygen content versus time doesn’t agree with the text. Specific example: “About 255 million years ago … the oxygen […]

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  3. Earth

    Changes in the Air

    Changes in the atmospheric concentration of oxygen through geologic time, some gradual and some drastic, have strongly shaped evolution among many types of creatures.