Markquill
Start free

CAIE A Level Biology 9700 · Selection and evolution

Selection and evolution: explain question

Explain5 marksChallenge

A biologist studies three populations of a butterfly species (Populations A, B, and C). Population A and B are separated by a mountain range, while Population B and C occur in the same valley but use different host plants (B uses grass, C uses nettles). The biologist measures the DNA sequence similarity (percentage of identical bases in a specific gene) between the populations:

Populations comparedDNA sequence similarity (%)
A and B98.5
A and C96.2
B and C95.1

Explain how these data support the theory of evolution and how speciation may have occurred in these butterflies.

0 words · 5 marks

No account needed for your first marks. Your answer is used only to mark it.

How this question is marked

5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.

Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.

More Selection and evolution questions

All Selection and evolution questions

Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.