Question

Why can't the living organisms use atmospheric nitrogen directly?

Answer 1

Living organism can't use atmospheric nitrogen directly because of its wrong chemical form, only nitrogen in nitrate or ammonia can be use by plants and only nitrogen in amino acids can be used by animals.

Answer 2

living organisms cannot directly use atmospheric nitrogen in its gases stage. there are some organisms like bacteria called rizobium which can fix atmospheric nitrogen. they live at the roots of legumes crops . they fix nitrogen into the soil and plants derive it . animals who directly or indirectly eat them obtain the nitrogen