Nutrient cycles Flashcards
How much nitrogen is in the air
79%
Why is nitrogen essential?
for the production of amino acids and nucleotides
lack of nitrogen is often a limiting factor in plant growth
Outline the nitrogen cycle
- nitrogen fixing bacteria convert N2 in the air into ammonia
- nitrifying bacteria convert ammonia into nitrites
- nitrifying bacteria then convert nitrites into nitrates
- plants absorb nitrates forming proteins
- plants are eaten and turned into proteins by animals
- N2 will be present in animal waste and plants and animals die
- saprobionts turn waste and dead matter into ammonia by ammonification
- denitrifying bacteria convert nitrates into nitrogen
What is nitrogen fixing bacteria?
Nitrogen-fixing bacteria are essential for maintaining soil fertility
- most nitrogen-fixing bacteria are free-living in the soil and fix nitrogen into ammonia
How deos nitrogen fixing bacteria form associations?
They can form associations with leguminous plants.
- their roots possess swellings called nodules caused by colonies of nitrogen-fixing bacteria
What do plants use the ammonia for
used to form amino acids/proteins
In return bacteria obtain carbohydrates and vitamins produced by the plant during photosynthesis
What is nitrification?
The oxidation of ammonia and ammonium ions in the soil into nitrites, then nitrates, by nitrifying bacteria
What is nitrifying bacteria?
aerobic microorganisms
ploughing aerates the soil providing oxygen to nitrifying bacteria increasing their number and the amount of nitrate produced from ammonium ions
What are nitrates used for
they are absorbed by plant roots by active transport and provide the source of nitrogen for the synthesis of proteins and nucleic acids
How do consumers obtain nitrogen?
from proteins and nucleic acids by feeding on either plants or on other animals that feed on plants
What is ammonification?
Nitrogen from organic compounds is made available when they die or excrete waste
- Ammonification is the production of ammonia from these compounds
What is the function of saprobiotic orgamisms
cause decay and break down animal and plant proteins into ammonia which forms ammonium ions in the soil
What is denitrification
conversion of nitrates into gaseous nitrogen
What is the function of denitrifying bacteria
reduce soil fertility by converting nitrates back into atmospheric nitrogen
Why is there more denitrifying bacteria in waterlogged soil
there is a shortage of oxygen which leads to a reduction in aerobic bacteria
What effect does ploughing have on soil
ploughing aerates soil reducing the number of denitrifying bacteria so that less nitrate is lost from the soil
Outline the phosphorous cycle?
- when animals and plants die phosphates turin into phosphates in sacrobionts
- saprobionts put phosphates in the soil
- plant and animal remains and waste may end up at the bottom of the sea as oceanic sediments and will form phosphate rocks
- phosphate rocks are ground up and dissolved to make artificial fertilisers
- fertilisers go onto plants and in soil
What is mycorrhizae
mutualistic relationship with fungi and plant roots
Describe mycorrhizae ?
Fungi consist of hyphae, long thin strands which connect with the plant roots and extend into the soil to increase the surface area for absorption of water and ions
In return fungi receive organic compounds such as glucose produced by the plant during photosynthesis
What is the function is phosphate ions?
used to from DNA and ATP and are passed through food chains thru feeding
What is the effect of lack of nitrates and phosphates in the soil
limiting factor to plant growth
What is a natural fertiliser
dead and decaying remains of plants and animals, manure and bone near
- as they decay, mineral ions are released, which are taken up by crop plants
What are artificial fertilisers
contain a mixture of inorganic compounds of nitrogen phosphorous and potassium (NPK)
How is nitrogen absorbed by plants?
in the form of nitrate ions by active transport
nitrogen is essential for the formation of proteins and nucleic acids
How is phosphorous absorbed by plants?
in the form of phosphates by active transport
Phosphorous is essential for the formation of ATP, NADP phospholipids, and nucleic acids
What are advantages of natural fertiliser
- not easily lost by leaching
- improves soil and increases humus levels, water retention and texture
What are disadvantages of natural fertilisers
- low nutrient content
- slow release of nutrients may contain plant/animal pathogens that cause disease
What are advantages of artificial fertilisers
exact composition is known - soil balance can be controlled
What are disadvantages of artificial fertilisers?
- leaching into rivers is more likely to cause eutrophication
- applies in concentrated form and can case osmatic damage to plants
- expensive & energy consuming to manufacture
What is leaching?
fertilises can be washed away into rivers and lakes. This may result in eutrophication
- usually happens when fertilisers are overused
- artificial fertilisers contain soluble nitrates and phosphates which may be leached more readily
What is eutrophication?
a large increase in nutrients in an aquatic ecosystem which is increased by the use of fertilisers with nitrates and phosphate
- it can cause a considerable change in species diversity particularly in terms of reducing the presence of aerobic species
Outline eutrophication
- Increased conc of nitrogen and phosphorus in water
- Algal bloom on surface of water
- prevents light from reaching submerged aquatic plants
- Both algae and plants die
- Saprobionts digest decaying matter. increased no. of microbes causes an increase in respiration
- O2 from water is used up
- Lack of oxygen causes organisms to die
Outline the carbon cycle
- CO2 is removed from the air by plants and used by photosynthesis
- Animals obtain their carbon compounds by feeding on plants
- Plants and animals respire 24hrs a day releasing CO2 into the air
- Saprobiotic bacteria and fungi decompose dead plants and animals, releasing CO2 into the air during respiration
- Dead animals/plants from fossil fuels which afre burened and release CO2 into the air during combustions
