B3 4: How humans can affect the environment

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4.1 The effects of the population explosion

  • The human population is increasing rapidly (about 7 billion).
  • Many people want and demand a better standard of living
  • We produce lots of waste and pollution (of waterways with sewage, air with smoke and gases and land with pesticides and herbicides)
  • Some effects affect areas miles away, for example acid rain
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4.2 Land and water pollution

  • Sewage needs to be treated or it can pollute the land and water with gut parasites
  • Household and industrial waste can pollute land near landfill sites
  • Herbicides and pesticides used in agriculture can be washed into rivers.
  • Toxic chemicals in water can kill fish and aquatic plant life
  • Fertilisers and untrested sewage can increase number of nitrates in water
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4.3 Air Pollution

  • Burning fuels can produce sulphur dioxisw and other acidic gases.
  • Sulphur dioxde dissolves in water in the air, forming acidic solutions
  • Solutions then fall as acid rain, which can kill organisms, change the soil pH, and can stop reactions due to denaturing enzymes.
  • It can affect organisms both directly, and indirectly.
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4.4 Deforestation and peat destruction

  • Forsets are cut down to clear land for farming.
  • Deforestation leads to a reduction in biodiversity and an increase in carbon dioxide in the atmosphere.
  • Destruction of peat bogs also releases carbon dioxide as it is partly decomposed plant material; and use of this as compost completes decomposition and releases 'locked-up' carbon dioxide.
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4.5 Global Warming

  • Global Warming: The rise in the Earth's average temperature due to human activity and the greenhouse effect.
  • Greenhouse effect: The trapping of infrared radiation from the Sun as a result of greenhouse gases, such as carbon dioxide and methane.
  • Increasing the temperature of the Earth of only a few degrees may: cause changes in the Earth's climate, cause a rising sea level due to melting of ice caps and glaciers, cause changes in the migration patterns of birds and change the distribution of species.
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4.6 Biofuels

  • Biofuel is fuel produced from biological material. Two types of fuel are biogas and ethanol-based fuels
  • Glucose is produced from maize starch through digestion by carbohydrase
  • Ethanol-based fuels can be produced by fermentation of sugars from plants such as sugar cane.
  • The ethanol distilled from the fermentation product can be used as fuel in motor vehicles
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4.7 Biogas

  • Biogas is mainly methane. It is made by the anaerobic fermintation of a wide range of waste substances and plant material containing carbohydrate.
  • Biogas can be made on a large or small scale
  • Many different microorganisms are involved in biogas production.
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4.8 Making food production efficient

  • Short food chains make food production more efficient as less energy is wasted, so it is much more efficient ot eat plants than animals.
  • We can produce food more efficiently by preventing excercise (movement) so energy isn't wasted on movement; but this is seen as cruelty and is controversial. Keeping animals in warm sheds reduces energy wastage from maintaining body temperature.
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4.9 Sustainable food production

  • Sustainable food production involves managing resources and finding new types of food such as mycoprotein. This ensures there is enough food for the current population and in the future.
  • Fish stocks can be maintained by controlling fishing quotas and net size.
  • Mycoprotein is produced from the fungus fusarium and is grown aerobically on cheap sugar syrup from waste starch.
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4.10 Environmental Issues

  • Human activities affect both local and global environments.
  • There is a lot of evidence for environmental change.
  • Scientists need to check the validity and the reproducibility of the data collected.
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