Why did world (human) population begin to rise so rapidly from the mid 1900s?
Modern medice and faming methods were introduced, which have reduced the number of people dying from disease and hunger.
What are the three types of human caused pollution? Give examples for each
Water: Sewage and toxic chemicals from industry, as well as fertilisers used in agriculture can be washed into rivers/lakes.
Land: Pestocodes and herbicides used for farming, we bury nuclear waste and dump a lot of household waste in landfill
Air: Smoke and gases from industry/methods of transport eg. sulfur dioxide can cause acid rain
Which four main human activities reduce the amount of land and resourced available to other organisms?
- Dumping waste
- Quarrying (for metal ores)
What are the three natural stores of carbon dioxide?
- Oceans, lakes ponds
- Green plants
- Peat bogs
What is the 'greenhouse effect'?
The greenhouse effect is caused by the build up of several 'greenhouse gases' in our atmosphere, particularly carbon dioxide and methane, which act like an insulating layer. They absorb most of the heat (from the sun)that would normally be radiated back into space and re-radiate it in all directions (particuarly back to Earth). The Earth is graduallt heating up as a result, this is known as global warming.
What are the three main reasons for deforestation?
- To provide timber for buiding/burning for heat/energy
- To clear more land for farming (either for food or biofuels)
- To produce paper
List the four main issues caused by deforestation
- More methane in the atmosphere
- More carbon dioxide in the atmosphere
- Less carbon dioxide absorbed by trees (amount of photosynthesis reduced)
- Less biodiversity (due to loss of habitat)
Deforestation often occurs to make room for crops like rice or for livestock like cows, how does this release more methane into the atmosphere?
- Rice is grown in warm, waterlogged conditions - ideal for decomposers. These organisms produce methane.
- Cows produce methane.
When forest is burnt, which two factors release carbon dioxide into the atmosphere?
- Carbon from the wood is released when trees are burnt
- Microorganisms feeding on dead wood release carbon dioxide as a waste product of respiration
How does destroying peat bogs release more CO2 into the atmosphere?
Bogs are areas of land that are acidic and waterlogged. Organisms that live in bogs don't fully decay when they die because there's not enough oxygen, so the carbon in the organisms is stored in the peat. Peat starts to decompose when the bogs are drained (for farmland/compost) so this stored carbon dioxide is released.
How can an ordinary person reduce the amount of peat bogs that are destroyed?
They can ensure they buy peat-free compost to reduce the demand for peat.
What are the 6 main consequences of global warming?
- Thermal expansion of the sea
- Ice continents/glaciers melt
- Changed weather patterns, more extreme weather frontiers (Hurricanes occur over sea that is warmer than 27 °C - warmer sea, more hurricanes)
- The distribution of wild animal and plant species will change
- Biodiversity could be reduced as some species struggle to survive in the new climate
- Change in animal migration patterns.
How do scientists collect evidence to show how the climate is changing?
- Satellities (measure snow and ice melt, can measure temperature of the sea surface)
- Temperature and speed of ocean currents measured
- Weather stations are constantly recording atmospheric temperatures and weather patterns
In order to substantiate conclusions about climate change, what two factors must be considered when recording evidence?
- Whether the area used is large enough
- Whether the time span used is large enough
How is ethanol made? Outline the process
The anaerobic fermentation of sugar
- Sugar cane juices can be used, or glucose derived from maize strach by the action of carbohydrase (an enzyme). It is then allowed to anaerobically ferment.
- The ethanol is distilled to separate it from the yeast and remaining glucose before it's used
What is the mixture of ethanol and petrol called? Give one example of a country where some cars are adapted to run on it
How is biogas made?
Lots of different microorganisms are used to produce biogas. They ferment plant and animal waste, which contains carbohydrates. Sludge waste (eg. from sewage works or sugar factories) can be used to make it on a large scale. Biogas generators must be kept at a constant temperature.
Biogas is usually about ..... methane and ..... carbon dioxide.
Biogas is usually about 70% methane and 30% carbon dioxide.
Why can't biogas be stored as a liquid? And what does this mean for it's use?
Biogas can't be stored as a liquid because it would require a ridiculously high pressure, so it must be used straight away.
What is the difference between batch and continous generators of biogas?
Batch make biogas in small batches, they're manually loaded with waste, whcih is left to digest, adn the by-products are cleared away at the end of each session.
Continous generators make biogas all the time, waste is continously fed in and biogas is produced at a steady rate.
What 3 features must every biogas generator have?
- An inlet for waste material to be put in
- An outlet for digested material to be removed through
- An outlet so that biogas can be pumped to where it is needed
What four factors must be considered when designing a biogas generator?
Cost: continuous are more expensive to build and run
Convenience: batch generators are less convenient because they have to be loaded, emptied and cleaned.
Efficency: Gas is produced best at about 35 °C (think about insulation, solar power)
Position: the waste will smell so best located away from homes. Generator best near waste source.
What are the environmental and economic advantages of biofuels? (6)
- Carbon dioxide released was taken in by plants recently, so they're 'carbon neutral'
- Doesn's produce significant amounts of sulfur dioxide or nitrogen oxides
- Burning methane as a biogas means it's not released into the atmosphere
- The raw material is cheap and readily available
- Biogas generators act as a waste disposal system
- Saves people in developing rural communities from collecting wood for fuel
What 3 methods can be used to improve the 'efficency' of food production?
- Reducing the number of stages in the food chain
- Restricting energy lost by farm animals
- Developing new food sources like mycoprotein
What percentage of plant material that beef cattle east becomes useful meat for humans to eat?
For a given area of ........ you can produce .......... food for humans by growing ........., rather than having grazing .........
For a given area of land you can produce more food for humans by growing crops, rather than having grazing animals.
List some methods used in 'intensive farming' and why are they used?
Maintaining temperature so the animals don't use energy keeping warm
Restricting movement of the animals (battery farms, fish tanks and calf crates) - reduces energy used and creates more space for more livestock to be kept, also easier for them to be medically examined regularly
- Lacing foods with nutrients and growth hormones - so the animals grow quickly and don't have to be kept for long
Antibiotics are given even if the animals aren't ill
List some issues with 'intensive farming' methods
- Many argue it's unethical as it doesn't give the animals any quality of life
- Crampt conditions increase spread of disease
- Chemicals residual might be left in the meat from growth supplements given to the animals (many worry this could have unknown effects)
- Controlling light and heat uses energy, and therefore contributes to the demand for fossil fuels - in addition to being expensive.
What is the fungus usually used to make mycoprotein?
Describe how mycoprotein is made