When allele frequency changes quickly and in small populations, this is known as

Random Genetic Drift

Explanation:

Most populations are small enough that, by chance, sampling will result in a different allele frequency from one generation to the next. This is called "Genetic Drift".

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.