Model B3 Upgrade: Model Answers 4

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Environmental changeHigher tier question

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© Oxford University Press 2011

Model B3 Upgrade: Model Answers 4

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Question (part 1)

Lichens are used as indicators of air pollution. Many species are killed by sulphur dioxide in the air. Lichens were studied in central London.

(a) Match up observations A, B, C, and D to the four explanations 1, 2, 3, and 4 on the next page. Write one number beside each letter.

Observations

A Some lichen species survived when the air was very polluted.

B The number of lichen species increased in the 1960s.

C Some lichen species started to grow more abundantly after many years of pollution.

D Some lichens species started to grow more abundantly when other species died out.

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Model B3 Upgrade: Model Answers 4

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Question (part 2)

Explanations

1 Lichens evolved resistance to pollution.

2 The air became cleaner after the 1954 Clean Air Act.

3 There was less competition from other lichens.

4 Some species of lichens are more tolerant of pollution than others.

[2]

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Model B3 Upgrade: Model Answers 4

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Question (part 3)

(b) The maps on the right show the distribution of a butterfly called the Brown Argus, in 1980 and 2000.

(i) Describe the change in distribution

between 1980 and 2000.

[2]

(ii) Suggest and explain one possible reason for the change in distribution of the Brown Argus

[2]

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Model B3 Upgrade: Model Answers 4

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Explanation of question

The focus of (a) is living indicators of environmental change. You are being tested on your understanding of variation, evolution, and competition.

In (b) (i), you are asked to describe one aspect of the data that has been provided. For two marks, make sure you include at least two points in the description.

Finally, in (b) (ii) you are being asked to apply your knowledge about variation, evolution, and competition to a new situation. Make sure you provide both a suggestion and an explanation for two marks.

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Model B3 Upgrade: Model Answers 4

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D–C answer

(a) A 4, B 2, C 3, D 3

(b) (i) The butterfly spread north.

comment

The explanation that this candidate has matched with C is incorrect. The candidate may have accidentally assigned the same explanation to both C and D. It is always worth double checking all of the options.

This response to (b) (i) is worth one mark only as it does not describe filling of gaps in the south.

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Model B3 Upgrade: Model Answers 4

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D–C answer (continued)

(ii) This is due to global warming.

comment

Although the candidate has given one possible reason for (ii), to get both marks they would need to explain why global warming may be relevant.

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Model B3 Upgrade: Model Answers 4

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B–A* answer

(a) A 4, B 2, C 1, D 3

comment

In (a), this candidate has correctly matched each observation with its explanation:

A – Some species survived because they were naturally more tolerant. These were mostly the flat rather than the feathery lichens.

B – The lichens increased after the Clean Air Act, as would be expected since they are sensitive to pollution.

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Model B3 Upgrade: Model Answers 4

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B–A* answer (continued) comment

C – Lichens grew bigger after many years because there was selection within the surviving lichens for individuals which were more resistant to pollution.

D – Growing bigger when other species died out indicates that there was less competition, which left more space, food, and light for the remaining lichens.

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© Oxford University Press 2011

Model B3 Upgrade: Model Answers 4

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B–A* answer (continued)

(b) (i) The butterfly spread northwards and also filled the gaps in the south.

(ii) The spread could be due to climate change. More butterflies survived the winter in the north because temperatures rose between

1980 and 2000.

comment

This is a correct description for (b) (i), worth two marks.

This is a sensible suggestion for (b) (ii). The butterfly survives the winter as a caterpillar or pupa. Other reasonable suggestions include a food source spreading further north.

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