National 5BiologySQAExam QuestionsUnit 3: Life on EarthEvolution of species

Evolution of species (SQA National 5 Biology): Exam Questions

Exam code: X807 75

13 mins6 questions
11 mark

Researchers investigated natural selection in a population of owls.

The graph shows changes to the percentage of owls with brown feathers over time.

Line graph showing the percentage of owls with brown feathers from 1983 to 2008, increasing from 10% in 1988 to 47% in 2008.

Which of the following statements is correct?

The percentage of owls with brown feathers

  • doubles between 1993 and 2003

  • increases continually between 1983 and 2008

  • increases more between 1988 and 1993 than in any other 5-year period

  • increases less between 1993 and 1998 than between 2003 and 2008.

Choose your answer

2
Sme Calculator1 mark

The number of light and dark peppered moths in a woodland were counted over a 5-year period.

The results are shown in the table.

Year

Average number of light variety moths

Average number of dark variety moths

1

200

60

2

180

100

3

140

160

4

120

180

5

100

200

The percentage of moths counted in year 4 that were the dark variety was

  • 20%

  • 40%

  • 50%

  • 60%

Choose your answer

3a1 mark

A wren is a small bird found in most parts of Britain.

A small bird with speckled feathers and a raised tail, perched on a textured rock, facing right, in a monochrome setting.

Wrens found on the St. Kilda islands, off the west coast of Scotland, differ from those found on the Scottish mainland in several characteristics including colour, size and wing length.

It is thought that the St. Kilda wren is evolving into a new species.

Suggest how scientists could prove that the St. Kilda’s wren is not yet a different species from the Scottish mainland wren.

How did you do?

3b1 mark

The following statements refer to the sequence of events in the possible evolution of a new species.

The statements are not in the correct order.

A A new species is formed.

B Natural selection occurs.

C Part of the mainland population become isolated on an island.

D Mutation occurs within each sub-population producing variation.

E Over time each sub-population becomes genetically different.

Rearrange the statements into the correct order by writing the letters into the boxes. The last box has been completed.

square rightwards arrow square rightwards arrow square rightwards arrow square rightwards arrow box enclose straight A blank

How did you do?

3c2 marks

Explain how natural selection results in the evolution of a species.

How did you do?

4a1 mark

Hawaiian honeycreepers are species of birds that have evolved from a single ancestor to have different shapes of beak. This is an example of speciation.

Line drawing of four bird heads with varying beak shapes and sizes, resembling different bird species. Each beak is distinctive in length and curvature.

For speciation to occur, a population must be split by an isolation barrier.

Name one type of isolation barrier.

How did you do?

4b2 marks

Different mutations occurred in each sub‑population of honeycreepers after a population was split.

(i) Name the molecule within a cell in which mutations would occur.

[1]

(ii) Name one environmental factor which increases the rate of mutation.

[1]

How did you do?

4c1 mark

Suggest the selection pressure that could have led to the differences in the honeycreepers shown in the diagram.

How did you do?

4d1 mark

Explain what is meant by the term species.

How did you do?

51 mark

A weather event called El Niño occurs in the Galapagos Islands every three years.

During this event, the iguanas on the islands can decrease in body length due to lack of food.

Marine iguana resting on a rough, textured rock beside the ocean, with spiky dorsal scales and a slightly raised head, captured in black and white.

Scientists calculated the decrease in body length of the iguanas and recorded their survival time.

The results are shown in the graph.

Bar chart showing average survival time of iguanas. Survival time increases with a decrease in body length: 0 mm (1.5 years), 1-20 mm (2 years), 21-60 mm (3 years).

Which of the following statements is true?

  • The iguanas that had the least decrease in body length survived for the longest time.

  • The decrease in body length made no difference to the survival time of the iguanas.

  • The iguanas that had the greatest decrease in body length survived for the longest time.

  • The iguanas that had the greatest decrease in body length survived for the shortest time.

Choose your answer

61 mark

Which of the following is the only source of new alleles in a population?

  • Mutation

  • Natural selection

  • Isolation

  • Speciation

Choose your answer