A laboratory investigates whether chemicals extracted from tree bark can inhibit the growth of bacteria.
Identical discs containing extracts from four types of bark are placed on agar covered with the same bacterium. The diameter of the clear zone around each disc is recorded.
| Bark extract | Oak | Beech | Birch | Ash |
|---|---|---|---|---|
| Diameter of clear zone in mm | 13 | 22 | 16 | 10 |
Which comparison agrees with the results?
The oak extract was more effective than the birch extract.
The beech extract was more effective than the birch extract.
The birch extract was less effective than the ash extract.
The ash extract was more effective than the oak extract.
181 exam-style questions on OCR GCSE Biology 6.3 Monitoring and maintaining health, covering 6.3.1 Health and disease, 6.3.2 Interactions between diseases, 6.3.3 Spread of communicable diseases, 6.3.4 Common infections and diseases, 6.3.5 Physical plant defence responses, 6.3.6 Chemical plant defence responses, 6.3.7 Detecting and identifying plant diseases, 6.3.8 White blood cells and platelets, 6.3.9 Non-specific defence systems, 6.3.10 The immune system, 6.3.11 Monoclonal antibodies, 6.3.12 Vaccines and medicines, 6.3.13 Aseptic techniques, 6.3.14 Discovery and development of new medicines, 6.3.15 Causes of non-communicable diseases, 6.3.16 Treatments for cardiovascular disease, 6.3.17 Lifestyle factors and non-communicable diseases, 6.3.18 Cancer, 6.3.19 Stem cells in medicine, 6.3.20 Gene technology in medicine, and 6.3.21 The human genome and medicine. Each one has a worked solution and a mark scheme showing where the marks go.