nutrient & Phosphorus cycle (3.5.4) Flashcards
define the nitrogen cycle
its the natural process in which atmospheric nitrogen enters the soil and becomes part of a living organism
why are microorganisms needed for the nitrogen cycle
they are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb, as nitrogen gas cant also be taken up through gas exchange due to its triple bond
how do saprobionts break down dead material ?
they do it by SECRETING ENZYMES out of there cells, so that this matter can be DIGESTED EXTERNALLY- this can then be absorbed by the saprobionts, saprobionts nutrition
describe how the action of microorganisms in the soil produces a source of nitrates for crop plants (5 marks)
1) DNA/protein/amino acids into ammonia/ammonium compounds
2) by saprobionts
3) ammonia/ ammonium into nitrites
4) Nitrite into nitrate
5) by nitrifying bacteria
6) Nitrogen into ammonia/ammonium
7) By nitrogen-fixing bacteria
what are the differences between nitrogen cycle and phosphate cycle
PHOSPHORUS CYCLE:
- no atmospheric involvement
- phosphate has a low solubility in water
- cycle takes longer/slower due to the points above
- Phosphorus is very reactive and never exists naturally in its elemental form.
NITROGEN CYCLE:
- Nitrogen is in the atmosphere in gas form
- nitrate is highly soluble in water
- cycle is faster due to the 2 points above
- Nitrogen gas is unreactive and exists naturally in its elemental form.
what is mycorrhizae
A mycorrhiza is an association between a fungus and a plant root.
how does Mycorrhizae help to facilitate the uptake of water and inorganic ions by plants
- fungus acts like a extension to the root system- increasing the surface area for water and uptake of inorganic ions
- the plant shares some of its carbohydrate with the fungus for respiration: a “mutualistic” relationship where both species benefit.
why is mycorrhizae important for a plants growth
its important for phosphate, which is a major limiting factor in plant growth due to the slower nature of the phosphorus cycle,so it helps increase the uptake of phosphate ions
How does Fertilisers increase plant growth by,
it provides the plants by providing more nitrate for making protein and more phosphate for making DNA.
what is the difference between leaching and eutrophication
leaching it the movement of water which has nitrate and phosphate into near by water bodies
eutrophication can be caused by leaching it is the increase of inorganic nutrient concentration in water bodies
what does inorganic mean
no carbon
what are the environmental issues/ effects of using fertiliser (6 points)
- the inorganic substances that are dissolved in the water move through the soil into a nearby water body
- causes an INCREASE of inorganic nutrients in the body of water
- encourages the growth of algae on the water surface
- algal bloom blocks sunlight- so that aquatic plants can’t photosynthesise so die
- SAPROBIONTIC BACTERIA AEROBICALLY RESPIRE as they decompose the dead plant- USE UP ALL OXYGEN IN WATER
- Fish can’t aerobically respire as there isn’t enough dissolved oxygen and therefore die
it takes longer for the nitrogen-containing substances to get in the lake when an organic fertiliser is used than when an inorganic fertiliser is used. explain why it takes longer when an organic fertiliser is used? (2 marks)
1) insoluble/less soluble
2) (molecules) require break down/ slow release
One farming practice used to maintain high crop yields is crop rotation. This involves
growing a different crop each year in the same field.
Suggest two ways in which crop rotation may lead to high crop yields.
(2)
Grow crops / plants with nitrogen-fixing (bacteria);
Accept: grow legumes / named example e.g. peas, beans, clover
Accept: fallow year
Accept: use different amounts of ions / nutrients
- (Different crops use) different minerals / salts / nutrients / ions (from the soil);
- (Different crops have) different pests / pathogens / diseases.
(2 max)
