B1b - Humans and their environment

B1b - Humans and their environment.

Core biology unit 2.

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Humans and their environment (increase - populatio

Humans compete with other living things for resources and space. As the world’s population continues to increase, and standards of living improve, there is serious danger of a permanent change to the global environment. Human activities have led to the pollution of the environment, and a reduction in the amount of land available for other animals and plants, which makes it difficult for some species to survive.

Population Growth - Many years ago population numbers were kept low because of the difficulty of finding food. Then the development of agriculture led to a population explosion that has accelerated enormously during the past 500 years. Unlike other species, humans can adapt and survive in almost all environments.

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Human Growth Population Chart

the population has rapidly increased since 1500 CE, from less than 1 million in 1500 CE to over 6 billion today. (http://www.bbc.co.uk/schools/gcsebitesize/science/images/126_population_growth.gif)

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Population increase (human impact - living standar

Standard of living - People in the developed world enjoy a high standard of living, with abundant food, cars and comfortable housing. People in the developing world have a lower standard of living, but many countries are catching up quickly.

Impact of humans - The world’s human population has passed 6 billion and continues to increase. The growth in the human population and the increase in the standard of living are putting strains on the global environment. Here are some of the ways in which this is happening:

  • Non-renewable energy resources, such as coal, oil and natural gas, are being used up rapidly
  • Raw materials are being used up rapidly
  • More waste is being produced
  • More pollution is being caused
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Deforestation

Forestry is sustainable as long as forests are allowed to replace themselves, or are replanted after felling, but often this is not done. The result is that the world’s forests are steadily shrinking. This process is called deforestation. It has some horrid consequences:

  • Forest habitats are destroyed
  • Soil erosion increases, which causes barren land, flooding and land slides
  • Atmospheric pollution is caused when forests are cleared by burning trees

Biodiversity - The term biodiversity refers not only to the number of different species, but also to all the variations within and between species, and all the differences between the habitats and ecosystems that make up the Earth’s biosphere.The loss of forests reduces biodiversity and we run the risk of losing organisms that might have been useful in the future - for example as sources of new medicines. There is also a moral responsibility to look after the planet and its resources.

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Waste and pollution in the environment

Pollution - Pollution is the addition of substances to the environment that may be harmful to living organisms. Population growth and increases in the standard of living cause more waste to be produced. If this waste is not handled correctly, it leads to pollution. The most obvious form of pollution is often simply just litter on the ground, but pollution can affect the air and water too.

Land fill -  Most rubbish is buried in landfill sites and not all of it is safe. Common household items can contain toxic chemicals such as poisonous metals and industrial waste is also discharged onto the land. Many farmers apply pesticides to improve their crops, but these can damage living things. Toxic chemicals can be washed from the land into rivers, lakes and seas harming wildlife.

Water pollution - Water pollution is caused by the discharge of harmful substances into rivers, lakes and seas.

Air pollutionThe most common source of air pollution is the combustion of fossil fuels. This usually happens from vehicle engines and power stations.

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Pollutants and their effect

These are common water pollutants and their effects...

  • Fertilisers - Damage to aquatic ecostyems
  • Sewage - Kills aquatic organisms and harms hman health
  • Toxic chemicals - Kills aquatic organisms and harm human health

These are common air pollutants and their effects...

  • Smoke - Soot on buildings and trees. In air, making it difficult to breathe
  • Carbon Monoxide - Poisonous gas
  • Carbon dioxide - Greenhouse gas that contributes to global warming
  • Sulfur dioxide - Contributes to acid rain

Lichens are plants that grow in places like rocks or tree bark.

  • Bushy lichens need really clean air (they are air pollution indicators)
  • Leafy lichens can survive a small amount of air pollution
  • Crusty lichens can survive in more polluted air

Where no lichens are growing, it means that the air is heavily polluted with SO2.

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Greenhouse Gases

Methane and carbon dioxide are greenhouse gases. They absorb heat energy and prevent it escaping into space. This keeps the Earth warmer than normal. The Moon has no atmosphere and has an average surface temperature of –18ºC and the Earth has an average surface temperature of 14ºC. So greenhouse gases aren't a bad thing in themselves, but too much of them in the atmosphere leads to global warming.

Extra methaneRice paddy fields produce methane gas, cattle does too. As the numbers of rice fields and cattle have increased, so has the amount of methane in the atmosphere.

Extra CO2Carbon dioxide is produced by fossil fuels. When land is cleared for timber and farms, there are fewer trees to remove carbon dioxide from the atmosphere by photosynthesis. Also, if the fallen trees are burned or left to rot more carbon dioxide is released into the atmosphere. 

As the concentration of greenhouse gases in the atmosphere has increased, so too has the average global temperature.

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Temperature rise per year chart.

The earth's global average temperature has risen from 13.5º C in 1860 to 14.4º C in 1995 (temperatures over a 5 year average).  (http://www.bbc.co.uk/schools/gcsebitesize/science/images/global_temp_graph.gif)

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Sustainable Development

Humans reduce the amount of land and resources available for plants and animals. This happens because of farming, quarrying, dumping waste and building.

Urbanisation - Urbanisation means the growth of cities. About half the world’s population live in cities, and most of the population growth in the future is expected to take place in cities. It is predicted that by 2015, the world’s six largest cities will each have more than 20 million inhabitants. These are some of the effects of urbanisation:

  • Increased pollution
  • Increased energy consumption
  • Land no longer used for food production
  • Loss of natural habitats
  • Decline of rural towns and villages as people leave them to live in cities

Sustainable development - Means improving our quality of life without damaging the quality of life for future generations. It's important to all inhabitants of the planet, that sustainable development is achieved.

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Questions

1. What is one consequence of an increasing human population?

  • More waste
  • Natural gas reserves will increase

2. Where is toxic waste released from?

  • From factories, farms and households
  • From nothing

3. Which of the following is not a greenhouse gas?

  • Methane
  • Carbon dioxide
  • Nitrogen
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