1.Nitrogen is important in building proteins needed by plants and animals.This nutrient also flowin the environment.The waste materials decomposed by bacteria forms part of the nitrogen cycle.The bacteria in the soil act on the decomposing bodies of plants and animals to form nitrites (another form of nitrogen) to nitrates.Nitrates are products of decomposition needed and used by plants.Nitrates are used by plants to form amino acids that are processed into proteins.They are important for the growth of plant and animal cells.They are the substances used to build plants rich in protein that are eaten by humans and animals.

2.Plants absorb nitrogen from the soil.Nitrogen must first be converted to ammonium ions.Certain bacteria in the soil decompose dead plants and animals.The decomposition forms compound called ammnia and nitrate in the soil.The diagram of the nitrogen cycle illustrates this.Nitrogen-fixation is a process that occurs when nitrogen-fixing bacteria convert nitrogen in the atmosphere into ammonia The soil`s supply of ammonia is further increased by decomposing organic materials or humus.

3.Carbon gas combines with oxygen gas in the atmosphere to form yhn67a colorless gass called carbon dioxide.Carbon dioxide (CO2)from the air as mentioned earlier is absorbed by green plants during photosynthesis.Thus,CO2 is an important element in the formation of roots,stems,leaves,flowers,fruits and seeds