Flashcards in 3.5.4 - Nutrient Cycling Deck (19)
What is a saprobiont?
They feed on the remains of dead plants and animals. They secrete enzymes and digest food externally, then absorb the nutrients they need.
What are hyphae?
Long, thin strands that make up the fungi.
What is a symbiotic relationship
A relationship where two organisms of different species interact.
What do plants and animals use nitrogen for?
Making proteins and nucleic acids.
What is nitrogen fixation?
When nitrogen gas in the atmosphere is converted into nitrogen-containing compounds.
What are Rhizobium?
Bacteria found in root nodules of leguminous plants. They turn nitrogen into ammonia.
What is ammonification?
When nitrogen compounds are turned into ammonia. This ammonia then forms ammonium ions.
Ammonium ions in the soil are changed into nitrogen compounds that can be used by plants (nitrates).
Name a bacteria that converts nitrites into nitrates.
Name a bacteria that converts ammonium ions into nitrites.
What term is used to describe the conversion of nitrates in the soil into nitrogen gas.
Why does denitrification occur in waterlogged soils?
Because denitrifying bacteria need anaerobic conditions to convert nitrates into nitrogen gas.
How does nitrogen get into an ecosystem?
By lightning, and artificial fertilisers.
Name 4 things plants and animals need phosphorus for?
How does phosphate get into the soil?
Phosphate ions in rocks are released into the soil by weathering.
When fertilisers are applied to fields next to a lake, nitrogen-containing substances from the fertilisers get into the lake.
(a) (i) Describe how the nitrogen-containing substances get into the lake.
dissolve (in soil water) / run-off / leaching
Describe how the presence of nitrates in a lake may eventually lead to the death of fish
1. increased growth / algal bloom
2. blocks light; less photosynthesis; plants die;
3. increase in decomposers / bacteria;
4. bacteria respire so less oxygen;
It is estimated that, each year, a total of 3 × 109 tonnes of ammonia are converted to nitrate. Only 2 × 108 tonnes of ammonia are produced from nitrogen gas. Explain the difference in these figures.
1. Ammonia formed by decay of nitrogenous waste by decomposition.
2. by action of decomposers / saprobionts;