Answer:
12. Protein 13. Atmosphere 14. Nitrogen fixation 15. Plants 16. Consumers 17. Urinate 18. Decay 19. Decomposers 20. Ammonia 21. Denitrification
Explanation:
<em>12. Protein</em>
Nitrogen is essential to organisms. It is the main constituent of amino acids, which is the building blocks of protein in organisms.
<em>13. Atmosphere</em>
Nitrogen occurs naturally as gas in the earth’s atmosphere, accounts for about 78% of gases found in the atmosphere. This gaseous Nitrogen which is inert cannot be accessed by plants and animals for use.
<em>14. Nitrogen fixation</em>
For plants to be able to use the gaseous Nitrogen in the atmosphere, Nitrogen fixation has to take place. It involves the turning of gaseous Nitrogen in the atmosphere into ammonia. Nitrogen atoms is combined with Hydrogen atoms by enzyme called “nitrogenase”. This enzyme is present in nitrogen-fixing bacteria.
<em>15. Plants
</em>
Nitrogen enters the food web when plants assimilate nitrogen compounds from the soil to form nucleotides, amino acids, and other important chemicals in life.
<em>16. Consumers
</em>
Consumers are mainly animals that feed on plants in an ecological food web in other to be able to use the amino and nucleic acids formed from Nitrogen as a major component. Consumers can be categorized as primary, secondary, and tertiary consumers.
<em>17. Urinate
</em>
Nitrogen is very much concentrated in the urine of animals and also in their faeces. As animals urinate, Nitrogen is being returned to the soil.
<em>18. Decay
</em>
Decay starts, as organisms die. The organisms start decomposing.
<em>19. Decomposers
</em>
Decomposers are the bacteria in the soil that break down the nucleic and amino acids in dead organisms into nitrates and ammonia through a process called ammonification
<em>20. Ammonia
</em>
This is the end result of the decomposition of dead organisms by decomposers
<em>21. Denitrification
</em>
Compounds of nitrogen are turned back into gaseous nitrogen by anaerobic bacteria. This prevents
