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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