35. Soil

Why must atmospheric nitrogen ($N_2$) be 'fixed' before most organisms can use it, and which organisms are primarily responsible for this process?

Why do plants and animals need nitrogen?

How do animals obtain nitrogen for use in synthesizing proteins?

Why do organisms require nitrogen?

Why can't plants and animals use nitrogen (N_2) directly as it is found in the atmosphere?

Which biogeochemical cycle describes how nitrogen moves through an ecosystem?

Which type of organism is primarily responsible for converting atmospheric nitrogen ($N_2$) into a form usable by plants?

Which of the following statements correctly describes nitrogen and its role as a plant nutrient?

Which of the following is primarily responsible for capturing atmospheric nitrogen ($N_2$) and converting it into a biologically usable form during nitrogen fixation?

Nitrogen fixation is carried out primarily by which of the following?

Which of the following organisms can fix nitrogen?

In root nodules, the plants provide __________, and the bacteria provide __________.

Legumes (members of the pea family) have roots with swellings called nodules that __________.

Which of these describes the initial interaction between Rhizobium and a soybean root?

The enzyme complex that catalyzes the conversion of atmospheric nitrogen to ammonia is __________.