Over the last 50 years, a species of butterfly in the UK has been recorded further north than before.
Over the same period, the mean temperature in the UK has increased as the concentration of carbon dioxide in the atmosphere has risen.
Which extra evidence would most strengthen the conclusion that the rise in temperature caused the change in distribution?
The southern edge of its range has also moved north over the same period.
Many more people now record butterflies in the north of the UK than before.
The food plant of the butterfly has also spread further north in this time.
The butterfly is now found in more places in the north than in any earlier year.
109 exam-style questions on OCR GCSE Biology 6.1 Monitoring and maintaining the environment, covering 6.1.1 Field investigation of distribution and abundance, 6.1.2 Human interactions and biodiversity, 6.1.3 Maintaining biodiversity, and 6.1.4 Environmental change and distribution of organisms. Each one has a worked solution and a mark scheme showing where the marks go.