A sunflower nursery has two enclosed growing areas. Each area contains one sunflower plant infected with a fungus, 20 healthy sunflower plants and the same number of aphids. All other conditions are the same. Ladybirds are released into one area. After three weeks, fewer healthy plants are infected in the area with ladybirds. Which explanation of this result is correct?
Ladybirds ate the aphids, so fewer vectors carried the fungus from infected plants to healthy plants
Ladybirds ate the fungus on infected leaves, so less fungus was available to infect healthy plants
Ladybirds ate the aphids, which were the fungal pathogens causing disease in the sunflower plants
Ladybirds caused infected leaves to fall, so the fungus was removed before aphids could spread it
133 exam-style questions on AQA GCSE Biology 3.3 Plant disease, covering 3.3.1 Detection and identification of plant diseases and 3.3.2 Plant defence responses. Each one has a worked solution and a mark scheme showing where the marks go.