knowledge- ETN

• Ammonia is further converted into nitrates (NO3-) through nitrification by nitrifying bacteria.
• Plants and animals require nitrogen to produce proteins and nucleic acids
• despite the atmosphere being 78% nitrogen gas , plants and animals cannot use nitrogen in this form. Hence plants and animals rely on bacteria to make nitrogen containing compounds.
• the four stages of the nitrogen cycle: Nitrogen fixation, Ammonification , nitrification and denitrification.
• An example of nitrogen-fixing bacteria is Rhizobium
• nitrogen fixing bacteria are found within root nodules of leguminous plants.
• nitrogen fixation is the process of converting nitrogen gas into nitrogen containing compounds
• nitrogen fixing bacteria convert nitrogen into ammonia , which then forms ammonium ions . these ions can then be used by plants
• nitrogen fixing bacteria have a symbiotic relationship with plants as the bacteria provide nitrogen containing compounds and the plants provide the bacteria with organic compounds
• Ammonification is the process of turning nitrogen compounds in waste products and dead organisms into ammonia by saprobionts. This ammonia then becomes ammonium ions.
• Nitrification is the conversion of ammonium ions to nitrites, followed by the conversion of nitrites to nitrates through oxidation reactions carried out by autotrophic chemoheterotrophs called nitrifiers.
• Denitrifying bacteria use nitrates in the soil during respiration . this process will produce nitrogen gas which will return to the atmosphere. this process occurs in anaerobic conditions.
• Phosphorus is required to make: the phosphate backbone of DNA ; phospholipids for cell membranes ; to regenerate RuBP in photosynthesis and other substances.
• Phosphorus is essential for energy , DNA ,mRNA , phospholipids and stages of photosynthesis.
• The phosphate cycle depends on weathering. Hence phosphate tends to be a limiting nutrient as it is found in low concentrations.
• in sedimentary rocks phosphorus typically exists as PO4 and is released when the rocks weather slowly over time leading to it leaching into water and soil
• phosphate is transferred from the soil into plants through active transport in the roots. phosphate is transferred between organisms through the process of feeding.
• Upon a plant or animals death (or excrement) saprobionts will break down the organic molecules and release phosphates back into the soil to be taken up into plants again.
• plants will often form a symbiotic relationship with a fungus that helps them obtain more phosphate from the soil in return for sugars from photosynthesis. These fungi are known as mycorrhizae.
• when an animal dies, its body decomposes releasing phosphate into the environment. The phosphate may then become incorporated into new biomass by autotrophic organisms such as bacteria and algae.
• the main source of phosphorous in the ocean is river runoff which contains dissolved phosphate. This can lead to eutrophication where algae blooms occur due to high levels of phosphate.
• one major source of phosphate in waste comes from sea birds in the form of guano, it returns large amounts of phosphates to soils in coastal areas.
• The harvesting of plants for agriculture disrupts the cycling of nutrients, this is because in nature plants will die and replenish nutrients in the soil but in agriculture this is not true and thus no new nutrients are recycled.
• Farmers can add extra nutrients including nitrogen and phosphorus to soils . This increases the productivity of the crop and improves the efficiency of energy transfer.
• Artificial fertilizers are inorganic and usually in the form of powder , pellets or dissolved in liquid. Ammonium nitrate is produced by the Haber process through nitrogen fixation.
• Natural fertilizers are obtained from animal manure, compost, and decaying vegetation.
• Farmers can use the technique of crop rotation (alternating growing crops for harvest and leguminous plants in fields). the leguminous will contain nitrogen fixing bacteria which will replace the nitrates lost from the soil and the plants can be left to decay.
• excessive use of fertilizers can change the balance of nutrients in the soil which can lead to plant death as it reduces water potential of the soil.
• Runoff of fertilizers can lead to eutrophication.
• to prevent eutrophication you can use natural fertilizers as the phosphorus in natural fertilizers is in large less soluble compounds.
• Eutrophication is where excessive mineral ions can leach into ponds or rivers. the large amounts of nutrients causes rapid growth in algae . these large amounts of algae lock out light on the surface and prevent it from reaching plants causing them to die. Then saprobionts feed on and decompose the dead plant matter. the bacteria then require large amounts of oxygen to respire . this deprives larger organisms of oxygen leading to their death.
• In any ecosystems, plants synthesize organic compounds from carbon dioxide in the air or dissolved in water.
• Energy transfers are never 100% efficient - each stage transfers energy to the surroundings as heat via respiration and chemical via excretion.
• Biomass can be measured be measured in terms of mass of carbon or dry mass of tissue per given area and is measured in g or kg per metre.
• The chemical energy store in dry biomass can be estimated using calorimetry ( the burning of a dry sample in pure oxygen in a sealed container.)
• Gross primary production: is the chemical energy store in plant biomass , in given area or volume.
• Net primary production: is the chemical energy store in plant biomass after respiratory losses to the environment have been take into account:

  • NPP = GPP-R
• Net production of consumers:

  • N=I-(F+R)
  • Primary and secondary productivity is the rate of primary or secondary production measured as biomass in one area and time.
• Animals:

  Reduce waste through respiratory energy by:

  • reducing movement.
  • heating enclosures
• Plants:

  Reduce energy waste by:

  • simplifying food webs by use of pesticides
  • reducing competition by removing weeds
  • using fertilizers to keep the soil nutrient rich.