cycles within ecosystems - nitrogen cycle

how much nitrogen gas (N2) does the atmosphere contain

78%

why is the nitrogen cycle important for plants and animals

because this N2 gas in the atmosphere is very unreactive and can't be used by plants and animals directly

why is nitrogen important

- needed for making proteins for growth

- so living organisms have to get it somehow

how do plants get their nitrogen and so what has to happen to nitrogen in the air

- plants get their nitrogen from the soil

- nitrogen in the air has to be turned into nitrogen compounds (such as nitrates) before plants can use it

how do animals get nitrogen

as part of the proteins they consume by eating plant or animals

what is nitrogen fixation

process of turning N2 from the air into nitrogen compounds in the soil which plants can use

what are the 2 main ways of nitrogen fixation

- lightning

- nitrogen -fixing bacteria -> some in soil + some in nodules on roots of some plants

how does lightning cause nitrogen fixation

- there is so much energy in a lightning bolt

- that it's enough to make nitrogen react with oxygen in the air

- to give nitrates

what are the 4 diff types of bacteria involved in the nitrogen cycle

- decomposers

- nitrifying bacteria

- nitrogen-fixing bacteria

- denitrifying bacteria

what do decomposers do

- break down proteins (in rotting plants and animals) and urea (in animal waste)

- and turn them into ammonia (a nitrogen compound)

- this forms ammonium ions in the soil

where can plants get their nitrogen

- from the nitrogen-containing ammonium ions in the soil

- from the nitrates and nitrites

simplified what do decomposers do

break proteins + urea -> ammonia -> ammonium ions in soil

how are ammonium ions formed

when ammonia is dissolved in water

what does nitrifying bacteria do

turn ammonia in decaying matter into nitrites then nitrates

(ammonia-> nitrites -> nitrates )

nitrification

converting ammonia/ ammonium -> nitrite/ nitrate

nitrogen-fixing bacteria

atmospheric N2 -> nitrogen compounds plants can use

denitrifying bacteria

nitrates -> N2 gas

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