B3- How Humans can affect the Environment

Question 1

What does sulfur dioxide pollution cause?

Answer 1

Acid rain.

Question 2

What are the effects of acid rain?

Answer 2

• 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 3

Explain what happens in eutrophication.

Answer 3

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 4

What has happened as a result of deforestation?

Answer 4

• 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 5

Why does deforestation occur?

Answer 5

• 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 6

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

Answer 6

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

Question 7

What is a peat bog?

Answer 7

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

Question 8

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

Answer 8

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 9

How may global warming affect the Earth?

Answer 9

• 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 10

How can bioethanol be produced?

Answer 10

By anaerobic fermentation using yeast.

Question 11

How can biogas be produced?

Answer 11

By anaerobic fermentation using bacteria.

Question 12

How is bioethanol made/fermented?

Answer 12

• 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 13

What are the advantages to using bioethanol?

Answer 13

✅Efficient.

✅Renewable.

✅No toxic gases are produced.

✅Carbon neutral.

Question 14

What are the disadvantages to using bioethanol?

Answer 14

❌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 15

Which gas is the fuel in biogas?

Answer 15

Methane.

Question 16

How is biogas made?

Answer 16

• 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 17

How can food production be made more efficient?

Answer 17

• 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 18

What is meant by ‘sustainable food production’?

Answer 18

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

Question 19

What is the problem with overfishing?

Answer 19

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

Question 20

How can overfishing be solved?

Answer 20

• 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 21

What type of food is produced by Fusarium?

Answer 21

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

Question 22

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

Answer 22

-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 23

Why is biogas not made immediately?

Answer 23

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