13.3 Nutrient Cycles Flashcards
How does energy enter an ecosystem
Via sunlight and leaves as heat
Describe the basis of a simple nutrient cycle
- The nutrient is taken up by producers (plants) as simple inorganic molecules
- The producer incorporates the nutrients into complex organic molecules. When the producer is consumed, the nutrient passes into consumers (animals)
- It then passes along the food chain when these animals are eaten. When the producers/consumers die, their complex molecules are broken down by saprobiontic microorganisms that release the nutrient into the soil in its original simple form
What are nitrogen ions used for
Proteins
Nucleic acids
How is the majority of nitrogen taken up
Taken up by plants through the soil. These ions are absorbed via active transport through the routes
What other way can nitrogen be taken up
The atmosphere contains 78% nitrogen, but only a small proportion of organisms can use this
What is the problem with nitrate ions and soil
Nitrate ions are very soluble and easily leach into the soil deep enough the plant roots cannot reach them
How are nitrate concentrations restored in natural ecosystems
By recycling the nitrogen-containing compounds
How are nitrate concentrations restored in agricultural ecosystems
By using fetilisers
Why is release of nitrate ions by decomposition important in natrual ecosystems
Because there are few nitrate ions available from other sources
What are the 4 stages of the nitrogen cycle
- Ammonification
- Nitrification
- Nitrogen fiaxtion
- Denitrification
What does each 4 stages of the nitrogen cycle involve
Saprobiontic microorganisms
What is ammonification
The production of ammonia from organic nitrogen-containing compounds
What compounds can be used to produce ammonia
Urea
Proteins
Nucleic acids
Vitamins
Describe the process of ammonification
Saprobiontic organisms, mainly fungi and bacteria, feed on faeces and dead organisms material, releasing ammonia, which then forms ammonium ions in the soil. This is where nitrogen returns to the ecosystem
What is nitrification
The obtainment of energy from chemical reactions involving inorganic ions. Example is the conversion of ammonium ions to nitrate ions in an oxidation reaction
Describe the process of nitrification
- Oxidation of ammonium ions to nitrate ions (NO2-)
2. Oxidation of nitrate ions to nitrite ions (NO3-)
What carries out the process of nitrification
Nitrifying bacteria that live in the soil
What do nitrifying bacteria require to carry out the conversion of ammonium ions to nitrite ions
Oxygen. Therefore soil is required to have air spaces
How do farmers ensure air spaces in soil
- Keeping soil structure light and well aerating it by ploughing
- Good drainage to prevent air spaces filling with water
What is nitrogen fixation
The process by which nitrogen gas is converted into nitrogen-containing compounds
What are the 2 types of nitrogen fixating microorganisms
- Free living nitrogen fixing bacteria
2. Mutualistic nitrogen fixing bacteria
What is free living nitrogen fixing bacteria
These bacteria reduce gaseous nitrogen into ammonia, which they use to manufacture amino acids
When they die and decay the nitrogen rich compounds are released into the soil
What is mutualistic nitrogen-fixing bacteria
These bacteria live in nodules on the roots of plants such as peas and beans
They obtain carbs from the plant and the bacteria obtain amino acids from the mutualistic nitrogen fixing bacteria
How does denitrification occur
When soils become waterlogged, and have a low oxygen concentration, the type of microorganism present changes.
There are fewer nitrifying and nitrogen-fixing bacteria present and more anaerobic denitrifying bacteria.
Why are anaerobic denitrifying bacteria bad
Because they reduce the availability of nitrogen-containing compounds for plants by converting soil nitrates into gaseous nitrogen
For land to be productive in terms of nitifying and nitrogen-fixing bacteria presence what must occur
The soil must be kept well aerated to prevent build up of denitrifying bacteria
What is phosphorus used in
ATP
Phospholipids
Nucleic acids
Where is the main resevoir of phosphorus ions
Mineral form than in the atmosphere. The P cycle completely lacks a gaseous form
How does phosphorous exist
As phosphate ions (PO43-) in the form or sedimentary rock deposits
Where are sedimentary rock deposits found and what happens to them
They are primarily found in the seas and are brought to the surface by geological lifting
Describe the phosphate nutrient cycle
- The weathering and erosion of sedimentary rock deposits help phosphate ions to become dissolved and available for absorption by plants which incorporate them into their biomass
- The phosphate ions pass into animals which feed on the plants
- Excess phosphate ions are excreted by animals and many accumulate in waste material, such as that from sea birds
- On the death of plants and animals, decomposers such as bacteria and fungi break them down - releasing phosphate ions into the water or soil. Some ions remain in parts of animals, like bones or shells, that are slow to break down
- Phosphate ions in excreta, released by decomposition and dissolved out of rocks, are transported by streams and rivers into lakes and oceans where they form sedimentary rocks, thus completing the cycle
What are mycorrhizae
Associations between certain types of fungi and the roots of a vast majority of plants
What do the fungi act as in mycorrhizae
Extensions of the root system, increasing the total surface area for the absorption of vitamins and minerals in the neighbourhood of the roots.
How do mycorrhizae play an important role in nutrient cycles
By improving the uptake of relatively scarce ions such as phosphate ions
How is the mycorrhizal relationship mutualistic
because the plant benefits from improved water and inorganic ion uptake, while the fungus receives organic compounds such as sugars and amino acids from the plant.
