Topic 8 - The Nitrogen Cycle (Paper 2) Flashcards
why is nitrogen from the atmosphere not included in the nitrogen cycle?
nitrogen gas in the atmosphere is very unreactive so cant be used directly by plants or animals
what is nitrogen needed for?
making proteins for growth
where do plants get their nitrogen from?
the soil. nitrogen in the air must be turned into nitrogen compounds before plants can use it
what is nitrogen fixation?
the process of turning nitrogen from the air into nitrogen compounds in the soil which plants can use
how does nitrogen fixation happen?
lightning - energy in a bolt of lightning makes nitrogen react with oxygen in the air to give nitrates
nitrogen-fixing bacteria in soil
what are the four types of bacteria involved in the nitrogen cycle?
decomposers, nitrifying bacteria, nitrogen-fixing bacteria and denitrifying bacteria
what do decomposers do?
break down proteins in rotting plants/animals and urea and turn them into ammonia, forming ammonium ions in the soil
what do nitrifying bacteria do?
turn ammonium ions in decaying matter into nitrates
what do nitrogen-fixing bacteria do?
turn atmospheric nitrogen into nitrogen compounds that plants can use
what do denitrifying bacteria do?
turn nitrates back into nitrogen gas
