K.C.S.E Biology Q & A - MODEL 2008PP2QN07
Describe the nitrogen cycle
During thunderstorm/ lightning; nitrogen gas combines with O2 to form nitrogen oxides; nitrogen oxides dissolve in water to for nitric acid; acid is deposited in the soil by rain, nitric acid combines with chemical substance to form nitrates/ nitric acids dissolves to form nitrates which are absorbed by plants symbiotic bacteria/ such as rhizobium; which are found in root nodules of leguminous plants, fix free nitrogen to nitrates.
Free living bacteria/ clatridium/ azotobacteria fix nitrogen to all rates
Nostoc algae/ chlorella/ anaemia/ ix nitrogen to nitrates.
Plants use Nitrates to form plant proteins
Animals feed on plants and convert plant proteins into animal proteins
Plants/ animals die and decomposed by bacteria/ saprophytes/ fungi decomposing plants/ animals/ release ammonia which is covered to nitrates/ by nitrosomomes nitrococcus bacteria
Nitrates are converted to nitrates; by nitrobacteria
Nitrates in the soil can be converted to free nitrogen/ denitrification by some fungi; pseudomonas/ hulobacillus denitrifying bacteria.