Nitrogen fixation and runoff of nitrogen applied to the soil pose problems for agricultural production and the environment. Why is this so? Explain
What will be an ideal response?
The soils that are overfertilized become depleted in nutrients and less fertile,
demanding more fertilizer. Also, runoff brings the applied chemicals into groundwater and
streams, where it can be ingested by humans. The phosphorus and nitrogen compounds
have been shown to have effects in humans in large quantities, and it is not known what
effects of exposure to small concentrations will be.
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As of early 2013, the number of confirmed exoplanets found was:
A) 5, all around stars within 20 light years of us. B) 42, all much bigger than Jupiter, but orbiting red dwarf stars. C) over 400, orbiting more than 300 stars. D) about 900, mainly around stars much smaller and fainter than our Sun. E) thousands, around every star we have closely examined to date.
You blow into an open pipe and produce a tone. What happens to the frequency of the tone if you place your hand over one end of the pipe and blow into it again?
A. depends on how hard you're blowing B. you hear the same frequency C. you hear a higher frequency D. you hear a lower frequency
The strongest magnetic fields in the photosphere lie near
A) sunspots. B) auroras. C) prominences. D) granules. E) flares.
Suppose that you live in Sydney, Australia (latitude 34°S). Describe the path of the Sun through your sky for each of the following days: a. the day of the spring equinox b. the day of the summer solstice c. the day of the winter solstice
What will be an ideal response?