nitrogen cycle
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The Nitrogen Cycle
IB Biology
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What is nitrogen?
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Periodic Table
•
Nitrogen is in the Nonmetals/BCNO Group
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Where is nitrogen found in the environment?
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The largest single source of nitrogen is in the atmosphere.
Nitrogen makes up 78% of our air!
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It is one of nature’s great ironies…
Nitrogen is an essential component of DNA, RNA, and proteins—the building
blocks of life. Although the majority of the
air we breathe is nitrogen, most living organisms are unable to use nitrogen as it exists in the atmosphere!
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How does atmospheric nitrogen get
changed into a form that can be
used by most living organisms?
NN
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By traveling through one of the four processes in the Nitrogen Cycle!
(1) Nitrogen Fixation
(3) Nitrification (2) Ammonification
(4) Denitrification
Nitrogen Cycle
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Nitrogen inthe air
animal protein
dead plants & animalsurine & faeces
ammonia
nitrites
nitrates
plant madeprotein
decomposition by bacteria & fungi
Azobacter
(nitrifying bacteria)
nitrates absorbed
denitrifyingPseudomonas denitrificans
root nodules(containing Rhizobium)
nitrogen fixing planteg pea, clover
Nitrobacter
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Your task!
• Imagine you are a nitrogen atom!
• Send postcard to your nitrogen friends explainig the following:
-Where you were…
-Where you are now….
-Where you are going next….
• Don´t forget to explain any meetings with bacteria or how you have changed as a molecule!
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Sewage
IB Biology
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Flushed with success?
Seoul, South Korea
Built by Sim Jae-Duck, involved with World Toilet Association
Why?
2 billion
To draw attention to the
people who do not have toilets or proper sanitation
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SewageWhat is it?
organic material
mineral salts
bacteria
What does it contain? examples
Untreated raw sewage is waste which has come from our toilets, sinks, baths etc.
Faeces, food fragments, enzymes, soap, gel, hair
Phosphates, nitrates
Food poisoning, disease-causing
Some from detergents & washing powders
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Environmental damage In rivers can cause algal blooms (as sewage is a
good food source for them), killing animals and plants living in water.
May release methane and ammonia gases (foul smelling).
Eutrophication
14 July 07
14 Sept 07Sussex River Ouse
Sea trout nursery
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Eutrophication
• High concentrations of inorganic substances can cause algal blooms
• Substances encourage rapid growth of algae and blue-green bacteria
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Biological Oxygen Demand
1. Sample of water measured at 20˚C over 5 days
2. Increase in organic pollutants increases number of bacteria
3. BOD will increase
Copy the steps above and give a reason as to why each step is
occurring-use your handout to help!
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Sewage treatment works
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Examples of diseases which may be spread by untreated sewage.
dysentery, typhoid, cholera
Why treat it?
May cause disease if it contaminates drinking water, due to harmful bacteria present.
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Sewage treatment process0 Untreated
raw sewage enters the sewage works
1a Screening (coarse filter)
Metal grids strain out large objects
Grit tank
Stones and heavy solids sink to the bottom
Lighter solids such as faeces sink to the bottom and form a sludge
1b
Sewage water to: 5
Aerobic conditions 3
Anaerobic conditions
4
2Sedimentation tank
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Sludge digestion tank
Bacteria feed on sludge, producing methane. Can be used as a fuel.
3
Anaerobic conditions
Activated sludge tank
Sludge mixed withextra air (oxygen), stirred, bacteria produce harmless liquids.
4
Aerobic conditions
Biological filter tank
Fluid from tank sprinkled over stones* coated with microbes. Bacteria produce harmless liquids
5
Treated waste emptied into rivers
6*or biobeads
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Now complete your Sewage Treatment cut and
paste sheet!
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Increasing energy levelsThe main fuels which can be obtained from biomass:
Biofuels
Methane
Alcohol
Both are products of fermentation
Methane (biogas) production occurs naturally by fermentation (anaerobic respiration) when animal or plant material decays.
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Generation of methane from biomass
1. Fermentation of faeces-aerobic bacteria hydrolyse carbs, proteins, fats
2. Oxygen used up -acetogenic bacteria convert sugars to short chain fatty acids (e.g. acetate), CO2 and H2
-acetogenesis stage
3. Methanogenesis-final stage is anaerobic and involves methanogenic bacteria-conversion of actetate to methane
Temp: 30-40˚C