i. Approximately 78% of air is nitrogen.

ii. Nitrogen is an abiotic component. It is a part of many molecules essential to life such as proteins, nucleic acids (DNA and RNA), ATP, and some vitamins.

iii. The nitrogen gas must be changed to a form called nitrates, which plants can absorb through their roots.

iv. The process of changing nitrogen gas to nitrates is called nitrogen fixation. It is carried out by nitrogen-fixing bacteria, Rhizobium, a biotic component.

v. The bacteria live in soil and roots of legumes, such as peas.

vi. Hence, interaction abiotic (nitrogen, soil) and biotic (bacteria, plants and animals) interact to use nitrogen in usable form.