The Nutrient Cycles

• nutrient is taken up by a producer as a simple, inorganic molecule
• producer incorporates the nutrient into complex organic molecules
• producer is eaten
• producers' nutrient is passed on to consumers
• nutrient passes along a food chain
• consumers die
• consumers' molecules are broken down by saprobiontic microorganisms
• saprobiontic organisms release the nutrient in its original form
• the cycle is then complete
• without decomposers, the cycle would back up (the nutrients would remain locked up)

• 78% of air on Earth
• gas at room temperature
• used for proteins, nucleic acids, amino acids and DNA
• many organisms use it due to its non-reactivity
• obtained by animals by eating plants
• enter plant by active transport in the roots, as nitrate ions (NO3-)
• nitrate ions are very soluble (easily leach through soil)
• ions are replenished by the decomposition of organisms
• there are very few sources of nitrate ions (usually from decomposition)
• nitrate ion concentration can be increased in agriculture by using fertilisers

What?

• fixes nitrogen gas (N2) to nitrogen compounds (organic nitrogen)
• ammonia is often produced (NH3)
• ammonia is used for amino acid production

How?

• free-living bacteria
  • reduce gasesous nitrogen to NH4+
  • produce amino acids
  • released from bacteria when they die and decay (into the soil)
• mutualistic nitrogen-fixing bacteria
  • live in nodules on the roots of plants
  • produce amino acids from gaseous nitrigen, which they give to plants
  • plants repay them with carbohydrates
• lightning
• industrially

What?

• production of ammonium ions from nitrogen compounds (ammonia)
• from urea (excess amino acids), proteins, nucleic acids and vitamins from faeces
• ammonium ions are NH4+

How?

• saprobiontic microorganisms
  • feed off urine, faeces and dead organisms (nitrogenous compounds)
  • release ammonia
  • returm nitrogen to a non-living form
  • become ammonium ions in the soil

What?

• oxidation of ammonium ions to nitrite ions (NO2-)
• oxidation of nitrite ions to nitrate ions (NO3-)

How?

• free-living nitrifying bacteria
• need well aeriated soil to respire and survive
• obtain their energy from chemical reactions involving inorganic ions
• house oxidation of ammonium ions and nitrite ions

Possibilities?

• taken into plant roots by active transport
  • released upon plant/consumer death
• converted back to nitrogen gas

What?

• nitrate ions are converted to nitrogen gas

How?

• anaerobic denitrifying bacteria
  • soil becomes waterlogged, causing low O2 levels (air can not aeriate)
  • aerobic bacteria decrease
  • anaerobic bacteria increase

• comes from a mineral
• comes mostly as phosphate ions (PO4^3-) in sedimentary
• phosphorylates molecules
• part ATP and DNA, RNA, etc
• in bones and teeth
• red phosphorus
  • used in fertilisers, detergents, steel production and matches
  • non-toxic
• white phosphorus
  • used in flares
  • glows in the dark
  • burns skin
  • poisonous 
• no gaseous exchange in its cycle

• sedimentary rock is always formed in aquatic environments
  • oceans and lakes
• sedimentary rock is made up bone fragments, bones, shells, molluscs and plants (coal)
  • is 8% of the Earth's crust

• brought to the surface by geological uplifting of rocks
• rock is eroded and dissolved in the soil

• plants obtain phosphorus from the soil
  • via active transport
  • through roots
• animals eat the plants and obtain phosphorus
  • use it for ATP, DNA, etc
• primary consumers are eaten by secondary
  • along a food chain

• animals die
• animals are decomposed by decomposers
• phosphates are released into water or soil
• remaining phosphates in excreta are released by decomposition
• phosphates are transported down stream
• phosphates are transported to lakes and oceans to form new sedimentary rock

• associations between certain types of fungi and the roots of plants
  • a mutualistic relationship
• fungi acts as an extension of the plant's root system
  • increases its surface area of the absorption surface for mineral ions
• fungi changes the composition of the soil (makes it spongy) 
  • holds more water to resist droughts
  • holds extra minerals
• insoluble phosphorus requires vast root system, without this aid
• plays a vital role in phosphorus absorption in uncultivated soil
• fungi supplies plants with phosphorus
• fungi receives sugars and amino acids in return