Nutrient Cycles Flashcards
(15 cards)
Describe the Nitrogen Cycle
-
Nitrogen fixation:
- Atmospheric nitrogen gas is converted into nitrogen-containing compounds so it can be absorbed by plants
- this is done by:
nitrogen- fixing bacteria that naturally occurs in the soil, convert nitrogen into ammonium
- directly in a pant through plant nodules as they contain bacteria that can covert nitrogen gas–> ammonium gas OR nitrate
ONLY FOR LEGIMUNUOS PLANTS -
Nitrification:
- convert ammonium–> Nitrites by nitrifying bacteria.
- convert nitrites into nitrates by nitrifying bacteria
ammonium –> nitrites–> nitrates -
Assimilation:
- nitrates in the coil are absorbed into the plant by active transport & then assimilated to be used for amino acids, ATP, DNA -
Ammonification
- animals eats the plants =nitrates get into animals
- animals decompose= nitrogen containing molecules (ATP, DNA, proteins) are broken down and digested by saprobionts -
Denitrification
- denitrifying bacteria convert nitrates back into nitrogen gas in the atmosphere
NITROGEN IS LOST
- this will only occur if not enough O2 in soil / if soil is water logged
How is nitrogen and nitrogen containing compound lost in denitrification?
- if the soil is waterlogged/ flooded
- not enough O2 in the soil
- denitrifying bacteria are are anaerobic therefore denitrification will only occur if there isn’t enough O2 in the soil
Describe the Phosphorous cycle.
- phosphate ions in oceans and soil will be absorbed by plants by active transport
- phosphate ions will be incorporated into plant DNA / phospholipids - phosphate ions in animals
- eat plant material and digest and absorb phosphate ions incorporate into their DNA/ phospholipids - phosphate ions from water and remains
- decomposition animals dies: phosphate ions broken down in remains
- excretions: phosphate ions in waste ( guano) - phosphate ions in rocks
- guano overtime deposits into rocks and starts to form phosphate ions into the rocks
- phosphate ions are eroded and return back into the ocean due to weathering
What are the roles of microorganisms in recycling minerals?
Saprobionts → decompose waste + dead matter via extracellular digestion, so inorganic ions available to other organisms
Nitrogen-fixing bacteria → convert Nitrogen gas into nitrogen containing compounds (e.g. ammonia which can be turned into ammonium ions)
Nitrifying → converts ammonia to nitrites, nitrites to nitrates
Mycorrhizal → increases SA to optimise water + mineral ion absorption
Why are fertilisers used?
Fertilisers can be used to add important mineral ions, such as ions of nitrogen, phosphorus and potassium, back into the soil.
What are natural fertilisers?
Natural fertilisers are made up of organic matter in the form of the dead and decomposing remains of organisms and waste products.
- not very concentrated
- large amounts needed
- released over long periods of time
What are artificial fertilisers?
Artificial fertilisers are made up of inorganic chemicals
- concentrated
- smaller amounts needed
What are the environmental issues caused by fertilisers?
Leaching → Eutrophication
Describe the process of eutrophication.
- Excessive nutrients from fertilisers run-off from the land to the water → this causes excessive growth of algae on surface of water
- This blocks sunlight so aquatic plants below the surface die as they are unable to photosynthesise
3.The algae also start to die when competition for nutrients becomes too intense - Decomposing bacteria feed on the dead organic matter and also increase in number, as they respire aerobically, these bacteria use up the dissolved oxygen in the water
- As a result, the amount of dissolved oxygen in the water rapidly decreases, so aquatic organisms such as fish and insects may be unable to survive
Advantages of fertilisers (natural)
Cheaper & often free if farmer owns animals.
Disadvantage of fertilisers (natural)
The exact minerals & proportions can’t be controlled.
Advantage of fertilisers (artificial)
They’re chemicals created to contain exact products, therefore meet the needs for crops
Disadvantage of fertilisers (artificial)
Can cause leaching (when large quantities of ions are washed away w/ rainfall) & are more expensive.
what are mycorrhizae
fungi which are found locked around plant roots
adv of mycorrhizae
- increases the SA of roots for water & mineral absorption
- hold minerals and water around the roots which is beneficial if rainfall is low
- improve uptake of phosphate ions
