3.16 Plant defences
6 exam questions worth 11 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Give two physical defences that stop pathogens entering a plant.
Mark scheme
Any two from:
- cellulose cell walls (1)
- (tough) waxy cuticle (1)
- bark / layers of dead cells (1)
Model answer
A waxy cuticle on the leaves and cellulose cell walls.
Explain how bark protects a tree from pathogens.
Mark scheme
- layer of dead cells / acts as a barrier (1)
- falls off, taking pathogens with it (1)
Model answer
Bark is made of layers of dead cells that form a barrier. When the outer layers fall off, the pathogens on them fall off too.
Which is a mechanical defence?
Choose one answer.
Correct Not quite: the answer is Thorns
Mark scheme
D: thorns
Model answer
D: thorns deter animals from touching or eating the plant.
Foxgloves make poisonous chemicals. Explain how this helps the plant survive.
Mark scheme
- poisons deter herbivores / animals from eating the plant (1)
- so more leaves for photosynthesis / plant survives to reproduce (1)
Model answer
The poisons put herbivores off eating the plant, so it keeps its leaves for photosynthesis and survives to reproduce.
Name a medicine that was developed from a plant chemical, and the plant it came from.
Mark scheme
- aspirin (1) from willow (1)
- or digitalis (1) from foxgloves (1)
Model answer
Aspirin, which was developed from a chemical in willow bark.
Mimosa leaves fold up when they are touched.
Suggest how this protects the plant.
Mark scheme
- knocks off / dislodges insects (1)
- makes the plant look smaller / less appetising / deters herbivores (1)
Model answer
Folding up knocks insects off the leaves and makes the plant look less appetising to animals.
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