Lichens are used as indicator species for the amount of air pollution.

Lichens are sensitive to the amount of sulfur dioxide in the atmosphere.

Air pollution is generally higher in town centres than in the countryside.

Lichens are made up of two different organisms: fungi and algae.

Living together is advantageous for both fungi and algae.

What biological name is given to a relationship where both organisms benefit?

Lichens are sensitive to pollutants like sulfur dioxide because they take up chemicals from the air.

The photographs show two different species of lichen.

Bushy lichens are usually more sensitive to pollution than crusty lichens.

Use the photographs to suggest why.

Scientists investigated the relationship between lichen species and distance from a city centre:

• On a map, the scientists drew a transect line from the countryside to the city centre.
• The scientists examined sites every 200 metres along the transect line.
• At each site, the scientists recorded the lichen species growing on trees and walls.

The graph shows the scientists' results.

The lines on the graph show the range of each lichen species.

Give one way in which the scientists could have obtained more accurate results.

Which species of lichen can grow in the most polluted air?

Which species of lichen grows in the least polluted air?

Which species of lichen can grow in the widest range of environmental pollution?

One of the scientists concludes it is possible to tell how much sulfur dioxide is in the air by analysing the amount of species C growing’.

Suggest two reasons why this is not a valid conclusion.

Eutrophication is an environmental issue of concern for wetlands, streams, rivers, lakes, and reservoirs worldwide.

Which human activity can cause eutrophication of lakes?

During eutrophication, what is directly responsible for the increase in decomposers?

Describe the process of eutrophication and the effects that it can have on the environment.

The presence or absence of some organisms in an area can tell us about the area's levels of pollution.

What is the name given to organisms that can tell us about an area's levels of pollution?

Give the name of an organism which provides evidence for clean water.

Explain why sewage pollution in the river can decrease the oxygen levels in the water.

The photograph below shows a cheetah.

The cheetah is an endangered species, with just over 7,000 cheetahs remaining in the wild.

Scientists are worried that the cheetah might become extinct.

Explain the meaning of the term "extinct".

Which activity will be least likely to lead to the extinction of species?

What is not a reason for having conservation programmes?

Explain why it is important to conserve the cheetah's food supply and all the species that inhabit their ecosystem.

Farmland expansion is responsible for 90% of deforestation around the world.

Deforestation leads to decreased biodiversity.

When trees are removed it can become more difficult for other plants and animals to survive.

Give one reason why.

Name one type of toxic chemical used on farmland.

Suggest three ways that ecologists may try to increase biodiversity.