1
Triple only
[2 marks]Describe two physical barriers that help to protect plants from pathogens.
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- leaf cuticle: a waxy layer that pathogens cannot easily pass through (1)
- cell wall: a strong layer around the cell that pathogens must get past (1) allow made of cellulose
2
Triple only
[2 marks]Some plants make chemicals as a defence against attack. State one way these chemicals protect the plant and one way they can be used by humans.
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- kill / slow the growth of microorganisms, or poison pests (1) allow deter pests from eating the plant
- used as medicines to treat disease or relieve symptoms (1) allow a named example such as aspirin from willow
3
Triple onlyHigher tier
[4 marks]A farmer notices spots on the leaves of some of her tomato plants. Describe how the cause of the spots could be found.
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- eliminate environmental causes, for example check soil nutrients, water supply or temperature (1)
- record where the affected plants are / distribution analysis, for example clusters around one point suggest a spreading pathogen (1)
- observe the visible symptoms and compare them with known diseases (1)
- diagnostic tests in a laboratory to identify the pathogen (1)