Nutrient Cycles Flashcards
(27 cards)
What are saprobionts?
Saprobionts are microorganisms such as bacertia and fungi which live on detritus (pieces of dead organic matter).
How do nutrient cycles rely on saprobionts?
Saprobionts break down organic molecules into simple inorganic molecules and ions which plants can make use of.
How do saprobionts feed?
Saprobionts feed by extracellular digestion.
1) The saprobionts secrete digestive enzymes.
2) Then they absorb the soluble nutrients released.
3) Then they convert organic molecules into inorganic compounds.
What are some examples of the organic molecules that saprobionts convert into inorganic compounds?
Saprobionts can convert DNA, amino acids, proteins, urea, into smaller inorganic ions such as phosphates and nitrates.
What is the purpose of detritivores?
Detritivores break larger leaves into smaller pieces which increases the surface area for the saprobionts to act upon, increasing the rate of decomposition.
Why is the nitrogen cycle important?
Even though the air is 78% nitrogen, plants and animals cannot obtain nitrogen through gas exchange due to its triple bond meaning that microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb
State 3 examples of biological molecules containing nitrogen.
ATP, nucleic acids, and proteins.
What are the key stages of the nitrogen cycle?
1) Nitrogen fixation
2) Ammonification
3) Nitrification
4) Denitrification
What happens during nitrogen fixation?
Nitrogen gas is converted into ammonium compounds by nitrogen-fixing bacteria which can be free-living in the soil, or may live within root nodules of legume plants. Ammonium compounds are converted into nitrates, which are then absorbed by plants and used to build plant proteins.
What happens during ammonification?
Nitrogen from living organisms is returned to the soil in the form of ammonia by the action of saprobionts which forms ammonium ions in the soil.
What happens during nitrification?
The ammonium ions in the soil are converted into nitrates by nitrifying bacteria; some bacteria convert ammonium ions into nitrites, and other bacteria then convert nitrites into nitrates.
What happens during denitrification?
Denitrifying bacteria use nitrates in the soil for respiration in anaerobic conditions, such as in waterlogged soil.
Why is the phosphorous cycle important?
Plants and animals require phosphorus for production of phospholipids, nucleic acids, and ATP.
What is the process of the phosphorous cycle?
1) Phosphorus in rocks is released into the soil and into water sources in the form of phosphate ions (PO₄³⁻) due to weathering.
2) Phosphate ions are taken up from the soil by plants, or absorbed from water by algae and transferred to consumers during feeding.
3) Phosphate ions in waste products and dead organisms are released into the soil or water during decomposition by saprobionts
4) The phosphate ions can be taken up and used again by producers, or may be trapped in sediments that may turn into phosphorus-containing rock once again
What are micorrhizae?
Micorrizhae are fungi that associate with the roots of the plants.
What is the function of micorrhizae?
Micorrhizae form a mutualistic relationship with the plant as they grow in and around the root system, increasing the surface area for absorption of water and mineral ions, while the micorrhizae receives sugars (e.g. glucose) from the plant.
What is the importance of the use of fertilisers?
Crops take in mineral ions from the soil to build their own tissues. When they are harvested, this means no mineral ions are returned to the soil as the crops don’t die and decompose there (phosphates and nitrates not returned to soil by saprobionts) so fertilisers are used to replace the lost mineral ions.
What are the two types of fertilisers?
Natural, and artificial fertilisers.
What are natural fertilisers?
Natural fertilisers are organic matter such as manure, dead and decaying remains of plants, animals, and slurry.
What are artificial fertilisers?
Artificial fertilisers are pure, inorganic ions, blended together to give the appropriate balance of mineral ions for a particular crop.
What is the importance of nitrate ions?
Nitrate ions are used in protein synthesis, ATP synthesis, and nucleic acids.
What is the importance of phosphate ions?
Phosphate ions are used in ATP synthesis, and nucleic acids.
What is the importance of potassium ions?
Potassium ions are used in stomatal regulation.
What is the importance of sulfate ions?
Sulfate ions are used in some amino acids which have a sulfur-containing R group.
