2. Living thing require nutrient cycles ( nitrogen cycle) because - Some organism ( decomposers) obtain energy from the break down of dead bodies and waste Raw materials (element like Nitrogen and Carbon) are recycled for use by the next generation.

3. Nitrogen is present in plants in the form of PROTEIN. The plants may DIE or they may be EATEN by animals. If they are eaten, the animal gains the PROTEIN. PROTEIN IN PLANTS PROTEIN IN ANIMALS DEAD BODIES CONTAINING NITROGEN nutrition death Death and excretion If plants die then nitrogen is in dead bodies The animals produce faeces, may die or they may be eaten by other animals. Nitrogen is in faeces or if animals die then nitrogen is in dead bodies or FAECES

4. Bacteria and fungi act as decomposers and break down the faeces and dead bodies. They produce AMMONIA which is a compound containing nitrogen. The plants are unable to absorb ammonia, so NITRIFYING BACTERIA change ammonia into NITRITE Another group of NITRIFYING BACTERIA will then change NITRITE into NITRATE which can be absorbed by the plant. AMMONIA NITRITE Nitrifying bacteria NITRATE

5. PROTEIN IN PLANTS PROTEIN IN ANIMALS DEAD BODIES CONTAINING NITROGEN nutrition death Death and excretion AMMONIANITRITE NITRATE Decomposers Bacteria and fungi Nitrifying bacteria Absorbed by plant roots and FAECES

6. Nitrogen can also be gained from the air. Special bacteria called NITROGEN FIXING BACTERIA live in the soil and take nitrogen out of the air and change it into soil nitrates.. NITROGEN IN THE AIR NITRATES IN THE SOIL Nitrogen fixing bacteria Other bacteria called DENITRIFYING BACTERIA break down the nitrates to release nitrogen back into the air. Denitrifying bacteria

7. Finally, there are a special group of bacteria, also called NITROGEN FIXING BACTERIA, which live in root nodules of clover plants. They also remove nitrogen from the air. However, the bacteria give this nitrogen to the plant. The plant will make protein. NITROGEN IN THE AIR PROTEIN IN PLANTS Nitrogen fixing bacteria in root nodules of clover plants

9. PROTEIN IN PLANTSPROTEIN IN ANIMALS DEAD BODIES and FAECES CONTAINING NITROGEN nutrition death Death and excretion AMMONIANITRITE NITRATE Decomposers Bacteria and fungi Nitrifying bacteria Absorbed by plant roots NITROGEN IN THE AIR Nitrogen fixing bacteria Denitrifying bacteria Nitrogen fixing bacteria in root nodules of clover plants

10. Lightning can also add nitrates to the soil. Nitrogen can be lost from the soil by means of denitrifying bacteria and leaching of nitrates into nearby rivers. PROTEIN IN PLANTSPROTEIN IN ANIMALS DEAD BODIES and FAECES CONTAINING NITROGEN nutrition death Death and excretion AMMONIA NITRATE Decomposers Bacteria and fungi Nitrifying bacteria Absorbed by plant roots NITROGEN IN THE AIR Nitrogen fixing bacteria Denitrifying bacteria Nitrogen fixing bacteria in root nodules of clover plants Leaching RIVERS Lightning NITRITE