Lightning can combine nitrogen with other elements, or be fixed, in order to be used by plants. In what way is most of the fixed nitrogen made available for use by plants?
It is incorporated
into the
exoskeletons of
flying insects that
eat plants,
It is inhaled and
exhaled by birds.
It is carried by rain
to the soil.
It is moved by the
wind toward dry
areas.

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What causes darkening of the skin as melanin production increases

Ras is a g-protein that is activated when a growth factor attaches to egfr. its activation results in the replacement of a gdp molecule with a gtp molecule, thus allowing a signal transduction pathway to be activated. considering the signal pathway illustrated on this page, what is one potential outcome of a mutation in the ras gene that leads to ras protein hyperactivity. be specific.