What do nitrifying bacteria do?
Reveal answer
Ammonium → nitrites → nitrates.
Key words: nitrates
5(c) CYCLES WITHIN ECOSYSTEMS · RECALL
5.11B The nitrogen cycle
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What do denitrifying bacteria do?
Reveal answer
Nitrates → nitrogen gas.
Key words: nitrogen gas
Where do nitrogen-fixing bacteria live?
Reveal answer
In root nodules of legumes (and soil).
Key words: root nodules
Why do plants need nitrates?
Reveal answer
Make amino acids → proteins.
Key words: proteins
Why does waterlogged soil lack nitrates?
Reveal answer
Anaerobic → denitrifying bacteria thrive.
Key words: anaerobic
What do decomposers turn proteins into?
Reveal answer
Ammonium compounds.
Key words: ammonium
Why plough soil?
Reveal answer
Aerates → nitrifying bacteria (aerobic) work.
Key words: aerates
What is meant by the term nitrogen fixation?
Reveal answer
Conversion of nitrogen gas into nitrogen compounds such as ammonium.
Key words: nitrogen fixation
What is meant by the term nitrification?
Reveal answer
Conversion of ammonium ions to nitrite and then nitrate by bacteria.
Key words: nitrification
What is meant by the term denitrification?
Reveal answer
Conversion of nitrate ions to nitrogen gas by bacteria.
Key words: denitrification
What is meant by the term root nodule?
Reveal answer
A swelling on legume roots containing nitrogen-fixing bacteria.
Key words: root nodule
Bacteria in the nitrogen cycle: for Nitrogen-fixing bacteria, give the conversion and the conditions favouring it.
Reveal answer
Conversion: Nitrogen gas → ammonium compounds. Conditions favouring it: Root nodules of legumes or free in soil.
Key words: Nitrogen-fixing bacteria
Bacteria in the nitrogen cycle: for Decomposers, give the conversion and the conditions favouring it.
Reveal answer
Conversion: Proteins and urea → ammonium ions. Conditions favouring it: Moist, warm soil with dead material.
Key words: Decomposers
Bacteria in the nitrogen cycle: for Nitrifying bacteria, give the conversion and the conditions favouring it.
Reveal answer
Conversion: Ammonium → nitrite → nitrate. Conditions favouring it: Well-aerated (oxygen-rich) soil.
Key words: Nitrifying bacteria
Bacteria in the nitrogen cycle: for Denitrifying bacteria, give the conversion and the conditions favouring it.
Reveal answer
Conversion: Nitrate → nitrogen gas. Conditions favouring it: Waterlogged, oxygen-poor soil.
Key words: Denitrifying bacteria
True or false, and why? “Plants absorb nitrogen gas from the air through their leaves.”
Reveal answer
False. Plants absorb nitrate (or ammonium) ions from the soil through roots.
True or false, and why? “Nitrifying and nitrogen-fixing bacteria do the same job.”
Reveal answer
False. Fixing bacteria convert N₂ to ammonium; nitrifying bacteria convert ammonium to nitrate.
True or false, and why? “Denitrifying bacteria help plants.”
Reveal answer
False. They remove nitrate from the soil, reducing the nitrogen available to plants.