A. Which form of nitrogen in the soil is NOT usable by organisms?

b. Why is this form not usable? Be specific.

c. How can this form be made usable to organisms?

A) Fixation. Nitrogen in its gaseous form (N2) can't be used by most living things

B) it can not be used because it most be converted or, 'fixed' to a more useable form. To do this it goes through a process called fixation. fixation is the change in a gene pool from a situation where there exists at least two variants of a particular gene (allele) in a given population to a situation where only one of the alleles remains.

C) This form can be made more usable if it's converted. It has to go through the process of fixation so the gene pool changes.