4.11B: Describe the Stages in the Nitrogen Cycle, Including the Roles of Nitrogen Fixing Bacteria, Decomposers, Nitrifying Bacteria and Denitrifying Bacteria (Specific Names of Bacteria are Not Required)

NITROGEN CYCLE: Process involved in recycling Nitrogen in the environment

THE NITROGEN CYCLE

Diagram showing the Nitrogen Cycle

EXPLANATION: NITROGEN - FIXATION As Nitrogen gas in the atmosphere is too unreactive to be used directly, it needs to be converted into soluble ions Hence, several processes ensure a constant supply of Nitrates Nitrogen-fixing Bacteria in Root nodules of Legumes will convert Nitrogen gas into Nitrates for use by Plants Lightning will convert Nitrogen gas into Nitrates Haber process in soil will convert Nitrogen gas into Ammonia, which Nitrifying Bacteria will convert into Nitrates These processes ensure a constant supply of Nitrates for use by Plants ABSORPTION BY PLANTS Plants will absorb Nitrates through their roots via active transport, producing Amino acids that form Proteins to increase biomass MOVEMENT ALONG FOOD CHAIN Animals in food chain will consume Plants to absorb Nitrogen found in Plant Protein, building Protein in Animal As a result, Nitrogen is passed along the food chain via feeding DEATH OF ORGANISMS Decomposers (e.g Bacteria and Fungi) will break down dead organisms and waste products of egestion / excretion to return Nitrogen compounds into the Soil in the form of Ammonium ions As a result, Nitrifying Bacteria will convert Ammonium ions deposited in soil into Nitrates for Plants to absorb DENITRIFICATION Denitrifying Bacteria in soil will break down Nitrates to return Nitrogen gas into the Air; this occurs in waterlogged soil and can hence be prevented by increasing drainage