Practise Plant defence responses. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Plants have physical, chemical and mechanical defences.
(a) Give two physical defences that help plants to resist invasion by microorganisms.[2]
(b) Some plants make poisons. Suggest how making poisons helps these plants to survive.[1]
(c) Which of these is a mechanical defence? Tick (✓) one box.[1]
Antibacterial chemicals
Bark
Thorns
Waxy cuticle
Show the answer and mark scheme
(a)
cellulose cell walls
a tough, waxy cuticle on the leaves
layers of dead cells on the surface of stems / bark, which fall off
(b)
poisons deter herbivores / animals from eating the plant
(c)Answer: Thorns
Question 2Medium8 marks
Plants defend themselves against pathogens and animals in different ways.
(a) Mint plants produce antibacterial chemicals. Explain how these chemicals help the plant.[2]
(b) The leaves of the sensitive plant droop and fold up when they are touched. Suggest two ways this could help the plant.[2]
(c) Explain how a waxy cuticle helps to protect a leaf against pathogens.[2]
(d) The bark of some trees is made of layers of dead cells that fall off. Explain how this helps to protect the tree.[2]
Show the answer and mark scheme
(a)
the chemicals kill bacteria / pathogens
(so) bacteria cannot infect the plant / cause disease
(b)
insects may be knocked off the leaves
the plant looks wilted / less appealing, so herbivores are less likely to eat it
a sudden movement may scare / deter animals
(c)
the cuticle is a barrier (covering the leaf surface)
(so) pathogens cannot enter the cells of the leaf
(d)
the dead cells form a barrier to pathogens
pathogens on the surface are lost when the dead cells fall off
Question 3Hard9 marks
Butterflies of one species lay their eggs on the leaves of passion flower plants. The caterpillars that hatch eat the leaves. A female butterfly will not lay eggs on a leaf that already has eggs on it. Some passion flower plants have small yellow spots on their leaves that look like the butterfly's eggs.
(a) Suggest how the yellow spots help to protect the plant.[2]
(b) Scientists counted the butterfly eggs on 30 plants with yellow spots and 30 plants without yellow spots. The mean number of eggs per plant was 1.8 on plants with spots and 6.3 on plants without spots. Calculate the percentage decrease in the mean number of eggs on plants with spots compared with plants without spots.[2]
(c) The white dead-nettle does not sting, but its leaves look very similar to the leaves of the stinging nettle. Suggest how this helps the white dead-nettle to survive.[2]
(d) Explain how passion flower plants with yellow spots could have become common over many generations.[3]
Show the answer and mark scheme
(a)
the butterflies mistake the spots for eggs / the plant mimics eggs to trick the butterflies
(so) fewer eggs are laid on the plant, so fewer caterpillars eat its leaves
(b)Answer: 71.4%
(6.3 − 1.8) ÷ 6.3 × 100
71.4 (%)
(c)
animals mistake it for a stinging nettle
(so) they avoid eating it
(d)
variation: some plants had spots because of a mutation / different alleles
plants with spots were eaten less, so were more likely to survive and reproduce
(so) they passed on the alleles for spots to their offspring