Nutrient cycles Flashcards
What are decomposers?
Organisms that break down dead and waste organic materials
How to saprotrophs feed?
○ Secrete enzymes onto dead waste material
○ Enzymes digest material into small molecules
○ Molecules then absorbed into the body
○ Molecules are stored or respired to releases energy
Why is nitrogen needed?
It is required to make proteins and nucleic acids for living things
What are saprobionts?
Bacteria that are involves in ammonification, nitrogen fixation, denitrification and nitrification.
What is mycorrhizae?
the symbiotic relationship between fungi and plants that enable plants to efficiently absorb water and inorganic ions from the soil
What is saprotrophic nutrition?
where digestion occurs extracellularly, e.g. by another organism with which the saprotroph has a symbiotic relationship
When does nitrogen fixation occur?
- When lightning strikes
- During the haber process
- When nitrogen fixing bacteria fixes it
What type of relationship does nitrogen fixing bacteria have with a plant?
A mutualistic relationship, as it provides it with nitrogen and, in return, receives carbon compounds.
What do chemotrophic bacteria do in nitrification?
They absorb ammonium ions
What condition is needed for nitrification?
Oxygen, so it should occur in well-aerated soil.
What occurs in nitrification?
Ammonium ions and nitrites are both oxidised to nitrates.
What occurs in denitrification?
- Bacteria can convert nitrates back to nitrogen gas
- When bacteria involved are growing under anaerobic conditions, they can produce nitrogen gas and nitrous oxide
What is eutrophication?
– Follows leaching
– Excess fertilisers in lakes cause overgrowth of algae
– Algae overgrowth blocks sunlight from penetrating deeper regions of water
– Plants rooted to the bottom of the lake cannot photosynthesise
– Therefore carbon dioxide builds up and oxygen isn’t produced
– Oxygen gets used up by animals living in the water
– Animals eventually run out of oxygen and suffocate
– Destruction of the ecosystem
How does agriculture disrupt nutrient cycles?
- They harvest crops before they can decompose
- Soil then becomes deficient of nitrogen and phosphorous
- Artificial fertilisers are used to replace lost nutrients
- fertilisers cause leaching
What is leaching?
– Rainwater leaks into soil and erodes land
– Fertilisers in the soil get drained by the movement of the rainwater towards bodies of water, e.g. lakes and streams
