Nitrogen is often in short supply in terrestrial ecosystems because
A) there is very little free nitrogen in the air.
B) most organisms cannot use atmospheric nitrogen.
C) there are frequent local shortages of atmospheric nitrogen.
D) nitrogen enters cells slowly because of its low solubility in water.
E) atmospheric nitrogen seldom comes into contact with terrestrial ecosystems.

Question

Quizplus · Accepted Answer

Although atmospheric nitrogen makes up about 78% of the air we breathe, most terrestrial organisms cannot use it directly. Nitrogen fixation by bacteria, lightning, or human activity is required to convert atmospheric nitrogen into a usable form, such as ammonia or nitrate. Therefore, nitrogen is often a limiting factor in terrestrial ecosystems.

Nitrogen Is Often in Short Supply in Terrestrial Ecosystems Because