Ammonia is first oxidised to nitrite by the bacteria Nitrosomonas and/or Nitrococcus. The nitrite is further oxidised to nitrate with the help of the bacterium Nitrobacter. These steps are called nitrification . These nitrifying bacteria are chemoautotrophs.
The nitrate thus formed is absorbed by plants and is transported to the leaves. In leaves, it is reduced to form ammonia that finally forms the amine group of amino acids. Nitrate present in the soil is also reduced to nitrogen by the process of denitrification. Denitrification is carried by bacteria Pseudomonas and Thiobacillus.
Charles Darwin's evolutionary theory enables us to establish cause and effect in biology, including those associated with a person's overall character. The evolutionary biologist Theodosius Dobzhansky wrote: "Nothing in Biology Makes Sense Except in the Light of Evolution". It's a well-known statement on the evolutionary theory and their implications in all spheres of biology