35. Soil

Which organisms are most critical in the nitrogen cycle due to their ability to fix atmospheric nitrogen?

Which of the following pathways indicates how nitrogen is added to the largest nitrogen reservoir (the atmosphere)?

How do animals and humans obtain usable nitrogen for their bodies?

Nitrogen gas ($N_2$) becomes converted into biologically usable chemical forms by what type of organism?

What role can lightning play in the nitrogen cycle?

How do animals obtain usable nitrogen for their biological processes?

Denitrification is an essential step in which of the following cycles?

In the context of nitrogen fixation, what role do lichens play in helping to create soil during primary succession?

How do plants obtain the nitrogen they need for growth?

How might the nitrogen cycle change if nitrogen-fixing bacteria and archaea went extinct?

How do herbivores obtain the nitrogen they need?

How do most plants obtain the nitrogen they need for growth?

Why is the nitrogen cycle important to humans?

Nitrogen enters the roots of plants in a process called:

Which process is responsible for converting atmospheric nitrogen gas ($N_2$) into biologically usable forms such as nitrite ($NO_2^-$) and nitrate ($NO_3^-$)?