B3 Part B

Question 1

Why did world (human) population begin to rise so rapidly from the mid 1900s?

Answer 1

Modern medice and faming methods were introduced, which have reduced the number of people dying from disease and hunger.

Question 2

What are the three types of human caused pollution? Give examples for each

Answer 2

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

Question 3

Which four main human activities reduce the amount of land and resourced available to other organisms?

Answer 3

1. Building
2. Farming
3. Dumping waste
4. Quarrying (for metal ores)

Question 4

What are the three natural stores of carbon dioxide?

Answer 4

1. Oceans, lakes ponds
2. Green plants
3. Peat bogs

Question 5

What is the ‘greenhouse effect’?

Answer 5

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.

Question 6

What are the three main reasons for deforestation?

Answer 6

1. To provide timber for buiding/burning for heat/energy
2. To clear more land for farming (either for food or biofuels)
3. To produce paper

Question 7

List the four main issues caused by deforestation

Answer 7

1. More methane in the atmosphere
2. More carbon dioxide in the atmosphere
3. Less carbon dioxide absorbed by trees (amount of photosynthesis reduced)
4. Less biodiversity (due to loss of habitat)

Question 8

Deforestation often occurs to make room for crops like rice or for livestock like cows, how does this release more methane into the atmosphere?

Answer 8

1. Rice is grown in warm, waterlogged conditions - ideal for decomposers. These organisms produce methane.
2. Cows produce methane.

Question 9

When forest is burnt, which two factors release carbon dioxide into the atmosphere?

Answer 9

1. Carbon from the wood is released when trees are burnt
2. Microorganisms feeding on dead wood release carbon dioxide as a waste product of respiration

Question 10

How does destroying peat bogs release more CO₂ into the atmosphere?

Answer 10

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.

Question 11

How can an ordinary person reduce the amount of peat bogs that are destroyed?

Answer 11

They can ensure they buy peat-free compost to reduce the demand for peat.

Question 12

What are the 6 main consequences of global warming?

Answer 12

1. Thermal expansion of the sea
2. Ice continents/glaciers melt
3. Changed weather patterns, more extreme weather frontiers (Hurricanes occur over sea that is warmer than 27 °C - warmer sea, more hurricanes)
4. The distribution of wild animal and plant species will change
5. Biodiversity could be reduced as some species struggle to survive in the new climate
6. Change in animal migration patterns.

Question 13

How do scientists collect evidence to show how the climate is changing?

Answer 13

1. Satellities (measure snow and ice melt, can measure temperature of the sea surface)
2. Temperature and speed of ocean currents measured
3. Weather stations are constantly recording atmospheric temperatures and weather patterns

Question 14

In order to substantiate conclusions about climate change, what two factors must be considered when recording evidence?

Answer 14

• Whether the area used is large enough
• Whether the time span used is large enough

Question 15

How is ethanol made? Outline the process

Answer 15

The anaerobic fermentation of sugar

1. 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.
2. The ethanol is distilled to separate it from the yeast and remaining glucose before it’s used

Question 16

What is the mixture of ethanol and petrol called? Give one example of a country where some cars are adapted to run on it

Answer 16

Gasohol

Brazil

Question 17

How is biogas made?

Answer 17

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.

Question 18

Biogas is usually about ….. methane and ….. carbon dioxide.

Answer 18

Biogas is usually about 70% methane and 30% carbon dioxide.

Question 19

Why can’t biogas be stored as a liquid? And what does this mean for it’s use?

Answer 19

Biogas can’t be stored as a liquid because it would require a ridiculously high pressure, so it must be used straight away.

Question 20

What is the difference between batch and continous generators of biogas?

Answer 20

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.

Question 21

What 3 features must every biogas generator have?

Answer 21

1. An inlet for waste material to be put in
2. An outlet for digested material to be removed through
3. An outlet so that biogas can be pumped to where it is needed

Question 22

What four factors must be considered when designing a biogas generator?

Answer 22

1. Cost: continuous are more expensive to build and run
2. Convenience: batch generators are less convenient because they have to be loaded, emptied and cleaned.
3. Efficency: Gas is produced best at about 35 °C (think about insulation, solar power)
4. Position: the waste will smell so best located away from homes. Generator best near waste source.

Question 23

What are the environmental and economic advantages of biofuels? (6)

Answer 23

1. Carbon dioxide released was taken in by plants recently, so they’re ‘carbon neutral’
2. Doesn’s produce significant amounts of sulfur dioxide or nitrogen oxides
3. Burning methane as a biogas means it’s not released into the atmosphere
4. The raw material is cheap and readily available
5. Biogas generators act as a waste disposal system
6. Saves people in developing rural communities from collecting wood for fuel

Question 24

What 3 methods can be used to improve the ‘efficency’ of food production?

Answer 24

1. Reducing the number of stages in the food chain
2. Restricting energy lost by farm animals
3. Developing new food sources like mycoprotein

Question 25

What percentage of plant material that beef cattle east becomes useful meat for humans to eat?

Answer 25

10%

Question 26

For a given area of ........ you can produce .......... food for humans by growing ........., rather than having grazing .........

Answer 26

For a given area of **land** you can produce **more** food for humans by growing **crops**, rather than having grazing **animals**.

Question 27

List some methods used in 'intensive farming' and why are they used?

Answer 27

1. **Maintaining temperature** so the animals don't use energy keeping warm 2. **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 3. Lacing foods with **nutrients and growth hormones** - so the animals grow quickly and don't have to be kept for long 4. **Antibiotics** are given even if the animals aren't ill

Question 28

List some issues with 'intensive farming' methods

Answer 28

1. Many argue it's unethical as it doesn't give the animals any quality of life 2. Crampt conditions increase spread of disease 3. Chemicals residual might be left in the meat from growth supplements given to the animals (many worry this could have unknown effects) 4. Controlling light and heat uses energy, and therefore contributes to the demand for fossil fuels - in addition to being expensive.

Question 29

What is the fungus usually used to make mycoprotein?

Answer 29

Fusarium

Question 30

Describe how mycoprotein is made

Answer 30

1. The fungus (Fusarium) us grown in fermenters, using glucose syrup as food. The glucose syrup is obtained by digesting maize starch with enzymes. 2. The fungus respires aerobically, so oxygen is supplied, together with nitrogen (as ammonia) and other minerals. 3. The fungus is constantly stirred by paddles. 4. The mycoprotein is then harvested and purified

Question 31

How are other microorganisms prevented from entering the fermenter in the production of mycoprotein?

Answer 31

The fermenter is sterilised, using steam. The incoming nutrients are heat sterilised and the air supply is filtered.

Question 32

Draw and label a diagram of a mycoprotein fermenter

Answer 32

Question 33

What are the advantages of mycoprotein?

Answer 33

1. In developing countries it can be difficult to find protein, this is a cheap and accesible alternative to meat (and doesn't neeed space to grae or nice grass to feed on) 2. Efficent way of producing protein 3. Microorganisms grow quickly and don't need much space. 4. Microorganisms can even feed on waste material that would be no good for feeding animals.

Question 34

Why is food distribution an issue?

Answer 34

Some food products have lots of 'food miles' as they're only grown in certain places/climates - this is expensive and also contributes to fossil fuel demand.

Question 35

Overfishing is decreasing fish stocks, which two methods are being used to reduce this issue?

Answer 35

1. **Quotas:** there are limits on the number, species and size of fish that can be caught in certain areas. 2. **Net size:** There are limits on the mesh size of the fish net, dependeing on what is being fished. This is to reduce the number of unwanted and discarded fish being caught, as well as allowing younger fishto slip through the net so they can reach breeding age.