A grower is investigating whether an insect pest lowers the yield of bean plants. The grower can use the same bean variety in the same field and season, with the same soil conditions and water supply. Which comparison would provide the best evidence for the effect of the pest?
Compare the yield with the pest present and absent, keeping the bean variety and growing conditions the same.
Compare the yield of two bean varieties, with the pest present on only one variety.
Compare pest numbers in two plots, with the bean variety and growing conditions the same.
Compare the yield before and after the pest arrives, keeping the bean variety the same.
127 exam-style questions on OCR GCSE Biology 6.2 Feeding the human race, covering 6.2.1 Biological factors affecting food security, 6.2.2 Agricultural solutions to growing demand, 6.2.3 Selective breeding, 6.2.4 Genetic engineering, 6.2.5 Steps in genetic engineering, 6.2.6 Benefits and risks of gene technology in agriculture, and 6.2.7 Biotechnological solutions to growing demand. Each one has a worked solution and a mark scheme showing where the marks go.