Biolody - B3.4 - How Humans Can Affect the Environment

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B3.4.1 - The Effects of the Population Explosion

  • Increasing numbers of people on th planet ~7 billion
  • Many people want and demand better standard of living - using up non-renewable raw materials - lots of industrial waste when producing goods - producing more waste and pollution
  • Reducing amount of land for animals and plants plants by building, quarrying, farming and dumping waste
  • Increasing population is affecting ecology of Earth
  • Humans polute:
    • waterways with sewage, fertiliser and toxic chemicals
    • air with smoke and gases, eg. SO2, contributing to acid rain
    • land with toxic chemicals eg. pesticides and herbicides, which can be washed into water
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B3.4.2 - Land and Water Pollution

  • Land pollution:
    • sewage must be treated to remove parasites and toxic chemicals
    • toxic chemicals can leak out from landfill sites - some waste is hazardous
    • farming methods can pollute land: herbicides and pesticides are poisons - can get in soil, food system and washed into rivers, chemical ferilisers to keep soil fertile can get into river
  • Water pollution:
    • herbicides, pesticides and chemical fertilisers get washed into rivers and streams
    • fertilisers and untreated sewage cause high level of nitrates in water
    • toxic chemicals from landfill leak into waterways and polute water, killing organisms, eg. fish
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B3.4.3 - Air Pollution

  • SO2 and other acidic gases are produced when burning fuels in cars and power stations
  • SO2 dissolves in water in air, forming acidic solutions - solutions fall as acid rain, often far away from where produced
  • Acid rain kills organisms, trees can be damaged of soaked for too long, changes soil pH - damages roots and may release toxic minerals, eg. aluminium ions, which damages organisms in soil and waterways, enzymes are very sensitive to pH so are affectecd by acid rain - when trees are damaged, food and habitats for other organisms are lost
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B3.4.4 - Deforestation and Peat Destruction

  • Deforestation: many trees cut down - large scale deforestation due to need for timber and land
  • Deforestation has: increased release of CO2 in atmosphere, due to tree burning or wood decay by microorganisms - reduced rate CO2 is removed by photosynthesis - reduced biodiversity due to loss of food and habitats
  • Deforestation occurred so crops can be grown to produce ethanol-based biofuels and to increase cattle and rice fields for food - cattle and rice produce methane
  • Destruction of areas of peat result in release of CO2 - occurs as peat is removed from bogs and used as compost, which is decayed by microorganisms - using peat-free composts means peat bogs won't be destroyed
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B3.4.5 - Global Warming

  • In normal natural balance, CO2 is released by respiration and used for photosynthesis - also dissolves in water - CO2 is sequestered by plants and water
  • Levels of CO2 and CH4 are increasing - called greenhouse gases and cause greenhouse effect - most scientists believe causes global warming
  • Increase of earth's temperature, even a few degrees, may:
    • cause big changes in climate
    • cause sea levels due to melting of ice caps and glaciers
    • reduce biodiversity
    • cause changes in migration patterns
    • changes in distrubtion of species
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B3.4.6 - Biofuels

  • Biofuels made from - two types: ethanol-based and biogas
  • Ethanol-based fuels produced by fermentation - microorganisms respire anaerobically to produce ethanol using sugars from crops as energy source -> glucose produced from maize starch by action of a carbohydrase -> glucose and sugar cane juices fermented by yeast producing ethanol -> ethanol extracted by disillation -> used as fuel in motor vehicles
  • Ethanol could replace fossils fuels in the future - terms of greenhouse effect, ethanol is more carbon friendly
  • Ethanol is carbon neutral - carbon dioxide used for photosynthesis by crops is returned when ethanol is burned
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B3.4.7 - Biogas

  • Biogas - mainly methane, produced during anaerobic fermentation by bacteria
  • Plants and waste material containing carbohydrate can be broken down in biogas generators - generators provide ideal conditions for bacteria to reproduce and ferment carbohydrates - must be maintained at suitable temperature in oxygen-free conditions - some generators designed to mix contents - generators either buried underground or have insulating jackets
  • Large scale, commercial generators use waste from sugar factories or sewage works - small scale, can be used by home or farm
  • Gas produced is fuel and provides energy for heating etc.
  • More methane in gas mixture = better quality of biogas
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B3.4.8 - Making Food Production Efficient

  • Shorter food chain = less energy wasted: more efficient to eat plants than animals
  • Produce meat more efficiently by:
    • preventing animal from moving: doesn't waste energy on movement - seen as cruellty
    • keeping animal in warm shed: doesn't waste energy on maintaining body temperature
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B3.4.9 - Sustainable Food Production

  • Human population increasing - food resources at risk of running out
  • Sustainable food production: manage resources and find new types of food - ensuring enough food for current and future population
  • Fish stock monitered - quotas and certain sized nets
  • Fusarium (fungus) grown to produce mycoprotein - new type of food - protein-rich, suitable for vegetarians - grown aerobically on cheap sugar syrup made from waste starch and the mycoprotein harvest
  • Microorganisms grown on large scale in fermenters - conditions in fermenter must be controlled for maximum growth of fursarium
  • Industrial fermenters: large vessels with air supply of oxygen for respiration, stirrers - spread out microorganisms and keep even temperature, water-cooled jacket - microorganisms release energy which makes heat, sensors - monitor pH and temperature
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B3.4.10 - Environmental Issues

  • Many human activities affect global environment: deforestation - increase levels of CO2, increase rice growing and cattle farming - more CH4 released, building dams to store water - loss of habitat, drying out river below dam, reduction in fertile land
  • Huge amounts of environmental data from different scientists in different countries - hard to know if data is valid and reliable
  • Different conclusions can come from the same data - often based on scientists opinions, can be biased
  • Global warming has divided opinion - some think increase in temperature is due to increased greenhouse gases, others think it's part of a natural cycle
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