B3- How Humans can affect the Environment

Question 1

How do humans pollute the environment?

Answer 1

• Waterways➡️Sewage, fertilisers and toxic chemicals.
• Air➡️Smoke and gases such as sulfur dioxide which contributes to acid rain.
• Land➡️Toxic chemicals such as pesticides and herbicides which can then be washed into the water.

Question 2

How can land be polluted by people?

Answer 2

• Sewage➡️Must be treated properly to remove gut parasites and toxic chemicals or these get onto land.
• Household and industrial waste➡️Placed in landfill and toxic chemicals leak out. Industrial waste like radioactive waste is very hazardous.
• Farming methods.
• Herbicides and pesticides➡️Poisonous, sprayed onto crops so can get into soil and food chain.

Question 3

How can water be polluted by people?

Answer 3

• Herbicides, pesticides and chemical fertilisers all get washed into rivers and streams.
• Fertilisers and untreated sweage can cause a high level of nitrates in the water.
• Toxic chemicals from landfill can leak into waterways and pollute water➡️Kills organisms such as fish.

Question 4

What does sulfur dioxide pollution cause?

Answer 4

Acid rain.

Question 5

What are the effects of acid rain?

Answer 5

• Buildings and statues with metals and rocks such as limestone are damaged.
• Damages the waxy layer on leaves, making it more difficult for trees to absorb the minerals need for healthy growth➡️Trees may die meaning food and habitats for other organisms are lost.
• Makes rivers and lakes too acidic for some aquatic life to survive.

Question 6

Explain what happens in eutrophication.

Answer 6

When fertilisers run off fields into water (sources), thick layers of algae grow along the surface.

This means that little or no light gets to the bottom so plants along the bottom die.

The dead plants decompose, and the micro-organisms doing this take up O₂ meaning there is not enough oxygen for bigger organisms so fish die.

Question 7

What has happened as a result of deforestation?

Answer 7

• More CO₂ has been released into the atmosphere during the burning of trees or the decay of the wood by microorganisms.
• Reduced rate at which CO₂ is removed from the atmosphere by photosynthesis.
• Reduced biodiversity due to loss of food and habitats.

Question 8

Why does deforestation occur?

Answer 8

• For growing crops to produce ethanol-based biofuels.
• Cattle and rice fields for food.
• Timber which can be sold and used to build with or as a fuel.
• To clear area in order to build settlements.
• HEP.
• Mining materials.

Question 9

How can deforestation lead to an increase in methane released into the atmosphere?

Answer 9

When the trees are replaced by rice fields and/or cattle, as both of these produce methane.

Question 10

What is a peat bog?

Answer 10

Peat bogs are made from plant material that does not decay (often because it is too cold or acidic).

Question 11

How can the destruction of peat bogs contribute to global warming?

Answer 11

Peat bogs contain plant material, therefore large stores of carbon.

This is returned to the atmosphere when the peat is burnt, or when the peat is used in compost for gardens and decayed by microorganisms.

Question 12

How may global warming affect the Earth?

Answer 12

• Causes big changes to Earth’s climate.
• Reducing biodiversity.
• Rising sea levels due to melting of ice caps and glaciers.
• Changes in migration patterns.
• Change in the distribution of species.

Question 13

How can bioethanol be produced?

Answer 13

By anaerobic fermentation using yeast.

Question 14

How can biogas be produced?

Answer 14

By anaerobic fermentation using bacteria.

Question 15

How is bioethanol made/fermented?

Answer 15

• Sugar cane juices/maize starch are fermented by yeast➡️Ethanol and CO₂ are made.
• Ethanol is purified by distillation.
• Bioethanol can be used as a fuel or added to petrol to form Gasohol.

Question 16

What are the advantages to using bioethanol?

Answer 16

✅Efficient.

✅Renewable.

✅No toxic gases are produced.

✅Carbon neutral.

Question 17

What are the disadvantages to using bioethanol?

Answer 17

❌A lot of plant material is needed.

❌Production is limited to countries with warm climates.

❌The space used to grow maize/sugar cane could instead be used for growing foods (to eat).

Question 18

Which gas is the fuel in biogas?

Answer 18

Methane.

Question 19

How is biogas made?

Answer 19

• Plant and animal waste is broken down in biogas generators.
• The generators are maintained at a suitable temperature (30^oC) in oxygen-free conditions➡️Ideal for bacteria to reproduce and ferment the carbohydrates.

Question 20

How can food production be made more efficient?

Answer 20

• The shorter the food chain, the less energy wasted➡️Eating plants instead of meat is more efficient.
• Reducing energy wastage by animals➡️Keeping the animals in warm sheds and preventing animals from moving.

Question 21

What is meant by ‘sustainable food production’?

Answer 21

Sustainable food production means producing food in ways that we can continue for many years.

Question 22

What is the problem with overfishing?

Answer 22

Overfishing can lead to stocks becoming so low that they are unable to replenish themselves.

Question 23

How can overfishing be solved?

Answer 23

• Introducing quotas➡️Restricting how many fish per year.
• Smaller nets with larger mesh size➡️So small, young fish can escape.
• Seasonal restrictions➡️I.e: ban fishing in breeding season.

Question 24

What type of food is produced by Fusarium?

Answer 24

Mycoprotein, which is a protein-rich food suitable for vegetarians.

Question 25

What are the features of a Fusarium fermenter and why?

Answer 25

• Air supply➡️To provide oxygen for aerobic respiration.
• Stirrers or gas bubbles➡️To keep the microorganisms spread out, nutrient concentration the same throughout and to provide an even temperature.
• Water-cooled jacket around outside➡️To keep cool as the respiring microorganisms release energy which heats the contents.
• Sensors➡️To monitor pH and temperature.

Question 26

Explain the advantages and disadvantages of factory farming animals (6marks).

Answer 26

-In intensive farming, animals are kept inside to maintain body temperature to limit energy lost from respiration to keep warm, and are close together to restrict energy lost from movement.

✅Advantages: animals grow faster and bigger as less energy is wasted from heat and movement and more energy is used for growth. This means that farmers have more animal/meat to sell.

❌Disadvantages: Considered unethical by the public so they may not want to buy the meat or pay as much.

Question 27

Why is biogas not made immediately?

Answer 27

The oxygen must be used up as methane is only produced by the bacteria through anaerobic fermentation.