Population and pollution

Question 1

There are many different types of pollution. Three that have caused much concern are:

Answer 1

• Carbon dioxide, from increased burning of fossil fuels, which may increase the greenhouse effect and global warming.
• CFCs, from aerosols, which destroy the ozone layer.
• Sulfur dioxide, from burning fossil fuels, which causes acid rain.

Question 2

What is exponential growth?

Answer 2

• The human population of the world is growing at an ever-increasing rate. This is called exponential growth.
• This growth in population is happening because the birth rate is exceeding the death rate.

Question 3

Where does the population increase the most?

Answer 3

The greatest rise in world population figures is occurring in under-developed land masses, such as Africa and India. However, the developed world uses the most fossil fuels (principally the USA and Europe).

Question 4

What is the carbon footprint?

Answer 4

The amount of pollution caused per person or organisation is called the ‘carbon footprint’. This measures the total greenhouse gas given off by a person or organisation within a certain time.

Question 5

What is a usual sign of low pollution?

Answer 5

If many different species are present in the habitat, this is usually a sign of low levels of pollution.

Question 6

How do direct methods measure pollution?

Answer 6

Direct methods include oxygen probe attached to computers that can measure the exact levels of oxygen in a pond. Special chemicals can be used to indicate levels of nitrate pollution from fertilisers.

Question 7

The presence or absence of an indicator species is used to estimate levels of pollution. For example:

Answer 7

• The mayfly larva is an insect that can only live in polluted water.
• The water louse, bloodworms and mussels can live in polluted water.
• Lichen grows on trees and rocks but only when the air is clean. It is unusual to find lichen growing in cities, because it is killed by the pollution from motor engines.

Question 8

There are advantages to the different methods of measuring pollution:

Answer 8

• Using indicator organisms is cheaper, does not need equipment that can go wrong and monitors pollution levels over long periods of time.
• Using direct methods can give more accurate results at any specific time.