The document discusses the nitrogen cycle, which is the biogeochemical cycle by which nitrogen is converted between its various chemical forms. It involves the conversion of atmospheric nitrogen into organic nitrogen by biological nitrogen fixation, which is carried out by bacteria and cyanobacteria. This fixed nitrogen is then assimilated by plants and converted to protein and nucleic acids. The nitrogen in organic matter is then converted back to inorganic forms through ammonification, nitrification, and denitrification, completing the cycle. The nitrogen cycle is essential for life on Earth as it regulates the nitrogen necessary for all organisms.

1. TOPIC : NITROGEN CYCLE
BY :
ARBIN SULTANA
1st semester 1st B.Ed
SSCE
TUMAKURU

2. INTRODUCTION OF NITROGEN
CYCLE

4. INTRODUCTION
 Definition.
 Interconversion into another forms.
 Important processes involved.
 Nitrogen cycle is of particular interest to
ecologists.
 Alteration in nitrogen cycle due to human
activities
 Effects of Global nitrogen cycle .

5. PROCESSES INVOLVED IN THE NITROGEN FIXATION
1.Nitrogen fixation
It is the process of conversion of atmospheric NO2
into forms useful to plants by lightning,bacteria
And cyanobacteria.
Nitrogen fixation includes three types:
1.Biological nitrogen fixation.
2. Industrial nitrogen fixation.
3. Atmospheric nitrogen fixation.

7. BIOLOGICAL NITROGEN FIXATION
ATMOSPHERIC
NITROGEN
AMMONIA
AMMONIUM ION

8.  Biological nitrogen fixation takes with the help of
microbes like Rhizobium.
 In biological nitrogen fixation nitrogen can be
converted into usable form with the help of living
organisms.
 This can be done by free living bacteria or symbiotic
micro organisms.
Free living bacteria Ex:Azatobacter,Rhodospirillium
Symbiotic micro organisms Ex: Rhizobium.
Cyanobacteria Ex:Nostoc, Anabaena.
Cyanobacteria fix atmospheric nitrogen both in free
state as well as in combined state.

9. SYMBIOTIC NITROGEN FIXATION
 Rhizobium leguminosarrum is a cyanobacteria that is
involved in the symbiotic nitrogen fixation.
 If the Rhizobium is not helping in the nitrogen fixation
then it is aerobic. If the Rhizobium is helping in
nitrogen fixation then it is anaerobic.
 Rhizobium has an enzyme called Nitrogenase this
nitrogenase is a Molybdenum and Iron containing
protein.
 Nitrogenase can work only in the anaerobic
condition.

10. INDUSTRIAL NITROGEN FIXATION
ATMOSPHERIC
NITROGEN
AMMONIA
UREA

11. ATMOSPHERIC NITROGEN FIXATION
MOLECULAR
(OXYGEN +
NITROGEN)
OXIDES OF
NITROGEN
NITRITES
AND
NITRATES

12. ASSIMILATION

14. AMMONIFICATION

16. NITRIFICATION AND DENITRIFICATION

18. CONCLUSION
Biogeochemical cycle are important because they
regulate the elements necessary for life on earth by
cycling them through the physical and biological
aspects of world. Biogeochemical cycles are a form of
natural recycling that allows continuous survival of
ecosystem. Nitrogen is crucial for all organisms
because it is an essential part of biological molecules
such as proteins and nucleic acid . Hence nitrogen
cycle is the most important because without it a lot of
organisms including humans would not be able to
survive.

19. REFERENCES
• www.indiaenvironmentportal.org.in
• www.sciencedirect.com
• www.science4u.com