Biology 6

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  • B6
    • Microbes
      • many bacteria cause disease but others are used in biotechnology; e.g. yoghurt making
      • antibiotic use has to be controlled as some bacteria are developing resistance; viruses are unaffected by antibiotics
        • bacteria exist in many different shapes but they all reproduce by binary fission and have certain cell structures in common
    • disease causing microbes can spread in many ways and have to be controlled using antiseptics and antibiotics
    • Biofuels
      • if bio-fuels are burnt at the same rate that they grow there is no net CO2 output however some areas of forest are being destroyed to grow them
      • biomass can be burnt and used as fuel; e.g. fast growing trees and products of fermentation such as alcohol or biogas
      • biogas does not produce much pollution as burning diesel or petrol but doesn't release as much energy as natural gas
        • biogas contains more than 50% methane, some CO2 and traces of other gases
          • alcohol produced by fermentation and mixed with petrol is called gasohol
    • Enzymes and genetic engineering
      • enzymes can be used in bio washing powders to convert stains to soluble products that can be washed away
        • because of the enzymes bio WP has to be used at a certain temp. and pH
          • enzymes can be immobilized in gel and used to lactose-free milk
            • DNA fingerprints can be made to allow organisms to be identified from their genes
              • various enzymes and plasmids allow genes to be transferre to produce transgenic organisms
            • sucrase is used to convert sucrose to glucose and fructose, which is sweeter and so less needs to be used in foods
    • Life in soil and water
      • water can be polluted by sewage or by fertiliser run-off
        • humus in the soil is important to life as it increases the air content and decays to release minerals
        • soil contains: differently sized mineral particles, different amounts of dead material and different amounts of air. all these factors are interrelated.
          • life in water is easier than on land because organisms do not dry out, temps do not vary much and water gives support however water content has to be controlled and water resists movement
            • earthworms are important in soil because they bury dead material so that it can decay, aerate the soil, mix up soil layers and neutralize acidic soil.
  • viruses use bacterial, plant or animal cells to reproduce themselves, destroying the cell in the process
    • bacteria can feed in many different ways and live in many different habitats
      • yeast are fungi and can reproduce rapidly if waste products are removed and they are given good and the ideal temperature and pH.
        • yeast is used in fermentation to make beer or wine. distillation is then used to make drinks with higher alcohol conc.
  • numbers of aquatic organisms vary during the year as light,temp and minerals vary
    • for food, marine organisms depend on plants, dead organisms floating down or bacteria acting as producers


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