Nutrients Flashcards
Nutrient cycles
Biogeochemical cycles involving elements essential to life
Where are nutrient cycles found?
- in living tissue/products of a living organism (passed through food chain)
- in solution (taken up by plants and microorganisms)
- in the atmosphere
- in soil and rocks (temporarily unavailable to organisms)
General pattern of nutrient cycles
- taken up by producers are simple, inorganic molecules
- producers incorporate the nutrient into complex organic molecules
- the producer is eaten- the nutrient passes onto the consumer and into the food chain
- when producers/consumers die, their complex molecules are broken down by saprobionts, that release the nutrient in its original, simple form
Why is nitrogen necessary?
For the production of proteins and nucleic acids
How does plants obtain nitrogen?
• Via nitrate ions (NO3-) actively transported from the soil
How do animals obtain nitrogen
• obtained via consumption
Nitrate ions
- INCREDIBLY soluble
* easily leach through soil, becoming unavailable to plants
Nitrogen fixation
- N2 (g) is chemically unreactive- must be converted into absorbable nitrogen compounds
- carries out by nitrogenase-positive nitrogen fixing bacteria of either the i) free living variety or the ii) mutualistic variety
Free living nitrogen fixing bacteria
- reduce N2(g) to ammonia (NH3)
- used to make amino acids
- nitrogen-rich compound release on decay
Describe mutualistic nitrogen fixing bacteria
- live in legume root nodules
- synthesise amino acids
- obtain carbohydrates
Equation for nitrogen fixation
N2 + 3H2 -> 2NH3
Nitrification
• oxidation of ammonium ions to nitrites to nitrates
Describe nitrifying bacteria
- free living
- chemoautotrophs (obtain energy from nitrification, because it is REDOX)
- aerobic -> aerated souls, oxygen water, drainage, ploughing
Ammonification
- produces ammonia from organic nitrogen-containing compounds (fæces, urea, cadavers) containing proteins, nucleic acids and vitamins
- saprobionts
Describe saprobionts
bacterial and fungal decomposers
Denitrification
- causée by lack of air chambers- waterlogging - reduced O2 concentration
- changes microorganism populations
- more denitrifying bacteria -> anaerobic
- convert soil nitrates to N2 (g)
- reduces amount of nitrogen-containing compounds a plant can synthesis
The phosphorous cycle
- no gaseous stage (no fixation) -> only found in mineral form
- weather and erosion of sedimentary rocks dissolve ions, allowing absorption and assimilation into biomass
- animals consume, excess excreted in waste
- some transported via waterways into waterbodies, forming sedimentary rocks (TAKES AGES)
Why is phosphorus necessary?
• nucleic acids, phospholipids
Where is phosphate found in nature?
(PO4)3- in sedimentary rock deposits
Mycorrhizae
- associations between fungi (extensions - increase SA for more H2O + mineral absorption) and plant roots (provide organic compounds - sugars, AAs)
- mutualistic
Why are fertilisers necessary?
- to stop soil mineral ion concentration getting dangerously low
- because they are constantly taken up by crops
Why does agriculture cause the need for fertilisers?
• producers are harvested and removed; cannot decompose; less recycling
Describe natural organic fertilisers
- dead and decaying plant and animal remains
* animal waste (manure, slurry, bone meal)
Describe artificial inorganic fertilisers
- mines from rocks and deposits, converted and blended
* nitrogen, phosphorus and potassium are almost always present
What gives the greatest long-term increase in productivity
Use of combination of natural organic and artificial inorganic fertilisers
Higher nitrogen levels
Promote growth, which promotes photosynthesis
Environmental issues of artificial inorganic fertilisers
- reduces species diversity (favours grasses, nettles and rapidly-growing species)
- leaching
Leaching consequences
- pollutes watercourses
* can result in eutrophication
Leaching process
- nutrients removed from soil due to rainwater dissolving soluble materials
- harmful is watercourses are potable
Describe eutrophication
1) nitrate ion increases; no longer a limiting factor of plant and algal growth; populations proliferate
2) algae grow at the surface; algal bloom absorbs light preventing it from reaching the depths
3) light becomes limiting factor for plants and algae lower down; death
4) saprobionts proliferate on dead matter, creating an oxygen demand (nitrates are released from decaying organisms)
• oxygen concentration decreases; limiting factor for aerobic respiration; death
• less competition for anaerobic organisms
• nitrates and toxic waste make water putrid
Give an example of toxic waste
Hydrogen sulphide
What, other than artificial inorganic fertilisers, may result in eutrophication?
- organic manure
- animal slurry
- human sewage
- ploughing old grassland
- natural leaching
