Nitrogen Cycle

Question 1

What do organism require nitrogen for

Answer 1

Organisms require nitrogen to make proteins.

Question 2

How much of the atmosphere you does nitrogen gas make up

Answer 2

Nitrogen gas (N2) makes up most of the atmosphere - 78%.

Question 3

Can organisms take up nitrogen as a gas

How can they take it

Answer 3

No

Organisms cannot take in N2 in gaseous form. They need to take in other forms of nitrogen e.g. nitrates (No3”).

Plants absorb their nitrogen from the soil in the form of nitrates and animals get theirs from the food they eat.

Question 4

A large amount of energy is used to change nitrogen gas into soluble nitrates. Name The three main ways are:

Answer 4

Lightning: Lightning strikes release sufficient energy to fuse nitrogen and oxygen into nitrates.

Fixation by legumes: Legumes are plants like peas, beans, and soya. They have a special type of nitrogen-fixing bacteria which live symbiotically in swellings called nodules on their roots. The bacteria convert nitrogen gas into a usable form such as nitrates. Nitrates are used by legumes and the bacteria are provided in turn with carbohydrates from the legumes.

Industrial processes: Artificial fertilisers containing nitrogen compounds are manufactured in industrial processes. They are very expensive to produce.

Question 5

Plant

Answer 5

Nitrogen-fixingbacteria and lightning convert N2, into nitrates.
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Nitrates are soluble and dissolve in soil water.
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Plants absorb nitrates from the soil and manufacture proteins.
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Plant proteins are consumed by animals and converted to animal proteins.
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Symbiotic nitrogen-fixing bacteria supply legumes with nitrates. (Bacteria get glucose from plant )

Question 6

Animals

Answer 6

.Animals release waste products such as urine and faeces from their bodies. These wastes contain nitrogen compounds, such as urea, which is then returned to the soil.

Question 7

Decomposes

Answer 7

. Decomposers break down these wastes products and the dead bodies of organisms and obtain their nitrogen this way. During decomposition, nitrogen compounds such as ammonia (NH2) are formed.

Question 8

Bacteria

Answer 8

. ? Nitrite bacteria convert ammonia to nitrites in the soil.

? Nitrate bacteria then convert nitrites (NO2) into nitrates (NO3 ), whichcan be absorbed by plants for the manufacture of proteins.
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Denitrifying bacteria in the soil convert nitrates into nitrogen gas