Unit 3- Humans and Their Environment

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Unit 3- Humans and Their Environment
1 Human Impact on the Environment
1.1 Population increase due too modern medicine and farming methods
1.1.1 Reduced number of people dying from hunger and disease
1.1.2 Graph shows the quick rise in population
1.1.3 Bigger effect on the environment we live in
1.2 Increasing Demands on the Environment
1.2.1 1) Pressure on Environment; resources we need to survive on
1.2.2 2) Demands for a higher standard of living e.g. luxuries like cars and computers So we use raw materials (e.g. oil to make plastics) but this means more energy is used for manufacturing processes More resources are being taken from the environment, more quickly
1.2.3 3) Raw materials used up quicker than being replaced. One day we're going to run out
1.3 Producing More Waste
1.3.1 Water Sewage and Toxic Chemicals pollute lakes, rivers and oceans Affecting plants and animals Wash away fetilisers
1.3.2 Land Toxic chemical used for farming Bury nuclear waste underground Lots of household waste in landfills
1.3.3 Air Smoke and gas in atmosphere pollute air e.g. sulfur dioxide ---> acid rain
1.4 More People means Less Land for Plants and Animals
1.4.1 Four main human activities: 1) Building 2) Farming 3) Dumping Waste 4) Quarring for metal ores
2 Carbon Dioxide and the Greenhouse Effect


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2.1 Carbon dioxide is removed from the air and stored in various places
2.1.1 1) Carbon Dioxide present in atmosphere
2.1.2 2) Many processes lead to CO2 being released
2.1.3 3) Too much CO2 leads to global warming
2.1.4 4) CO2 can be sequestered (locked up) in natural stores like: Oceans, Lakes and ponds Green plants; Photosynthesis Peat Bogs
2.2 Carbon Dioxide and Methane Trap Heart from the Sun
2.2.1 1) Temperature of Earth is balanced between heat it gets from Sun and heat it radiates back out into space
2.2.2 2) Gases in atmosphere act like an insulating layer. They absorb most of the heat that would radiate back into space and re-radiate it in all directions; back towards the Earth
2.2.3 3) If it didn't happen we would have no natural heat at night
2.2.4 4) The main Greenhouse gases are Carbon Dioxide and Methane; levels are rising sharply
2.2.5 5) Earth is heating up due to this rise. Global warming is a type of climate change
3 Deforestation and Destruction of Peat Bogs
3.1 Deforestation means Chopping Down Trees
3.1.1 This causes large scale problems such as cutting down rainforests. It's done for various reasons: 1) Provide timber to use as building material 2) Clear more land for farming so it can provide more food or be used for crops 3) To produce paper for wood
3.2 Deforestation leads to 4 main problems:
3.2.1 1) More methane in atmosphere Rice is grown in warm, waterlogged conditions, ideal for decomposers. These organisms produce methane Cattle produce methane
3.2.2 2) More carbon dioxide in atmosphere Released when trees are burnt Microorganisms feeding on dead wood release CO2 through respiration
3.2.3 3) Less carbon dioxide taken in Cutting down lots of trees means that the amount of CO2 removed from the atmosphere during photosynthesis is reduced
3.2.4 4) Less Biodiversisty Variety of different species in a habitat- more species, greater biodiversity Species become extinct from loss of habitat Lost opportunities: unknown products due to organisms being extinct, newly discovered plants and animals are a source of food, new fibres for clothing and new medicines
3.3 Destroying Peat Bogs Adds More CO2 to the Atmosphere
3.3.1 1) acidic, waterlogged land. Plant can't fully decay due to lack of oxygen. This builds up to form a peat.
3.3.2 2) Carbon in plants is stored in the peat
3.3.3 3) Drained so area can be used for farmland or cut up to be used as fuel. Also compost
3.3.4 4) Peat decomposes when drained so CO2 is released. Adds to greenhouse effect
3.3.5 5) People can buy peat-free compost to reduce the demand
4 Climate Change
4.1 The consequences of Global Warming
4.1.1 1) Seas gets warmer, it expands, causing sea levels to rise. People living in low-lying places will be flooded
4.1.2 2) Higher temperatures means ice melts, causing sea level to rise
4.1.3 3) Changed weather patterns; more extreme weather. Hurricanes form over water warmer than 27oC
4.1.4 4) Distribution on species may change. Conditions change, so they move to thrive in conditions that are best for them
4.1.5 5) Biodiversity reduce; extinction
4.1.6 6) Changes in migration patterns
4.2 Weight the Evidence Before Making Judgements
4.2.1 1) Scientist collect data
4.2.2 2) Satellites monitor snow and ice cover, temperature of sea surface. Detect changes
4.2.3 3) Only useful if it covers a wide area and long time scale
4.2.4 4) Mistakes happen
5 Biofuels
5.1 Fuels made by Fermentation
5.1.1 1) Waste products can be used
5.1.2 2) Bacteria or yeast break sugars by anaerobic respiration
5.2 Ethanol
5.2.1 1) Yeast make ethanol when they break down glucose by anaerobic respiration Glucose --> Ethanol + Carbon Dioxide + Energy
5.2.2 2) Sugar canes juices or glucose derived from maize starch by the action of carbohydrase
5.2.3 3) Ethanol distilled to separate the yeast from remaining glucose
5.2.4 4) Cars can run on Bioethanol and petrol; gasohol
5.3 Biogas made by Anaerobic Fementation of Waste Material
5.3.1 1) 70% methane, 30% carbon dioxide
5.3.2 2) Microorganism ferment plant and animal waste, contains carbohydrates. Sludge waste is used to make biogas
5.3.3 3) Made by fermenter called a digester or generator
5.3.4 4) Generators kept at constant temperature to keep microorganisms respiring
5.3.5 5) Batch generators and continuous generators
5.3.6 6) Biogas can't be stored as a liquid so is used straight away for heating, cooking, lighting or to power a turbine
5.4 Fuel Production; Large and Small Scale
5.4.1 Large Scale generators are being set up in countries. Small generators are used to power villages
5.4.2 Human waste, waste from pigs and food waste can be digested by bacteria to produce biogas
5.4.3 By-products are used to fertilise crops and gardens
6 Using Biogas Generation
6.1 Not all Biogas Generators are the same
6.1.1 Batch Generators make biogas in small batches. Manually loaded with waste which is left to digest and the by-products are cleared away at the end of each session
6.1.2 Continuous Generators make biogas all the time. Waste is continuously fed in and biogas is produced at a steady rate, more suited to large-scale biogas projects
6.1.3 Biogas generators need the following: 1) an inlet for waste material to be put in 2) an outlet for the digested material to be removed throught 3) an outlet so that the biogas can be piped to where it is needed
6.2 Four Factors to Consider When Designing a Generator
6.2.1 Cost: Continuous is more expensive than batch because waste has to be mechanically pumped in and removed
6.2.2 Convenience: Batch are less because they continually need loading, emptying and cleaned
6.2.3 Efficiency: Gas is produced more quickly at 35oC. If the temperature falls below this gas production is slower. Generators need to be insulated by solar heaters. No leaks or gas will be lost
6.2.4 Position: The waste will smell during delivery so generators are sited away from homes. Located fairly close to waste source
6.3 Using Biofuels has Economic and Environmental Effects
6.3.1 1) Greener alternative to fossil fuels. They are carbon neutral (except fossil fuels are needed for production)
6.3.2 2) Doesn't produce sulfur dioxide or nitrogen oxide which causes acid rain
6.3.3 3) Methane is given off from untreated waste
6.3.4 4) Raw material is cheap and avaliable
6.3.5 5) Digested material is better fertiliser; more crops
6.3.6 6) Saves drudgery
6.3.7 7) Waste disposal system; gets rids of animal and human waste
7 Managing Food Production
7.1 The "Efficiency" of Food Production can be Improved by....
7.1.1 1) Reducing the Number of stages in the Food Chain There's less energy and less biomass every time you move up a stage in a food chain. So for a given area of land, produce more food by crop growth than grazing animals. Reducing the number of stages. But still demand for meat products
7.1.2 2) Restricting the Energy Lost by Farm Animals Pigs and chicken intensively farmed; kept close together indoors in small pens, so that they are warm but don't move about. Saves them wasting energy and giving out heat. Grow faster on less food. It's cheaper for both the farmer and us
7.1.3 Developing New Food Source like Mycoprotein Mycoprotein means protein from fungi. Makes meat substitues for vegetarians. Fusarium is the main source of mycoprotein. Fungus is grown in fermenters, using glucose syrup as food. It is obtained by digesting maize starch with enzymes. Fungus respires aerobically. Sterilised using steam and air supply filtered, then harvested and purified It's an efficient way of producing protein. It grows quickly and doesn't need space. Uses waste materials
8 Problems with Food Production and Distribution
8.1 Efficient Food Production Involves Compromises and Conflict
8.1.1 1) Some people treating animals in unnatural and uncomfortable conditions is cruel. Growing demand for organic meat; not intensively farmed
8.1.2 2) Crowded conditions; increase spread of diesease
8.1.3 3) Antibiotics animals have can enter humans. This allows microbes that infect humans to become resistant to them
8.1.4 4) Animals need to be kept warm to reduce energy loss as heat. Powered by fossil fuels.
8.1.5 5) Fish stocks are low, yet fish feeds animals that are intensively farmed; animals wouldn't usually eat this food source
8.2 Food Distribution also Cause Problems
8.2.1 Some food products have lots of food mile, as they are transported a long way. Expensive and bad for the environment as fossil fuels are used which produced CO2 contributing to global warming
8.3 Overfishing is Decreasing Fish Stocks
8.3.1 Less fish to eat, ocean food chains are affected. We need to maintain fish stocks at a level where the fish continue to breed. This is sustainable food production; having enough food without using resources faster than they are renewed.
8.3.2 Maintained by: Fishing Quotas- limits on the number and size of fish that can be caught in certain areas. Prevent single species from being over fished Net Size- limits of the mesh size of fish net. Reduces number of unwanted fish; accidently caught. Younger fish will slip through the net allowing them to reach a breeding age