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

4.10: Describe the Stages in the Carbon Cycle, including Respiration, Photosynthesis, Decomposition and Combustion

CARBON CYCLE: Process that shows how Carbon is recycled between living organisms and the environment

THE CARBON CYCLE

Diagram showing the Carbon Cycle

EXPLANATION: RESPIRATION All living organisms exhale Carbon Dioxide into the atmosphere as a product of respiration to release energy for movement PHOTOSYNTHESIS Plants (producers) fix and remove Carbon Dioxide from the atmosphere via Photosynthesis to synthesize Carbon compounds for growth DECOMPOSITION Dead organisms and faeces from egestion are broken down by Decomposers to remove and return Carbon Dioxide gas to the atmosphere COMBUSTION If decomposition does not occur, incomplete decomposition over a long period of time may lead to fossilization of an organism to form fossil fuels, which when combusted, will return Carbon Dioxide back into the atmosphere