Plant defence responses

Question 1

Plants have a range of defence mechanisms to _______ and ___________

Answer 1

Plants have a range of defence mechanisms to infections and infestations

Question 2

State the three main defence systems against attack for plants

Answer 2

Physical defence responses to resist invasion of microorganisms.

Chemical plant defence responses

Mechanical adaptations

Question 3

Plants have _____ to prevent _____ from eating them

Answer 3

Plants have adaptations to prevent herbivores from eating them

Question 4

State some examples of physical defence responses to reduce the invasion of microorganisms

Answer 4

Examples of physical defence responses to reduce the invasion of microorganisms

Cellulose cell walls.

Tough waxy cuticle on leaves.

• Layers of dead cells around stems (bark on trees) which fall off.

Leaf fall

Question 5

Explain how cellulose cell walls is reduces the invasion of microorganisms

Answer 5

The cellulose cell wall not only provides support for the plant but also protection from microorganisms

Question 6

Explain why the actions of aphids are so damaging to plants

Answer 6

The aphids pierce the cellulose cell walls and breach the barrier. This gives pathogens a way into the cells

Question 7

Explain how tough waxy cuticle on leaves reduces the invasion of microorganisms

Answer 7

The tough waxy cuticle on the surface of leaves acts as a barrier to the entry of pathogens. It is only at the stomata that pathogens actually have access to the cells within the leaf.

Question 8

Explain how layers of dead cells around stems (e.g. bark on trees) reduces the invasion of microorganisms

Answer 8

Bark on trees, and a layer of dead cells on the outside of stems, form a protective layer that is hard for pathogens to penetrate. When the dead cells are lost or shed, the pathogens
fall off with them.

Question 9

Explain how leaf fall reduces the invasion of microorganisms

Answer 9

Deciduous trees lose their leaves in the autumn. Any pathogens that infect the leaves, such as rose black spot, fall off the tree when the leaves are lost.

Question 10

State some examples of chemical plant defence responses

Answer 10

Examples of chemical plant defence responses

Antibacterial chemicals.

Poisons to deter herbivores.

Question 11

Explain how antibacterial chemicals are a chemical plant defence response

Answer 11

Plants release antibacterial chemicals which kill bacteria and prevent them from attacking the plant

Question 12

Explain how poisons are a chemical plant defence response

Answer 12

Plants release poisons to deter herbivores from grazing on the plant.
Animals quickly learn to avoid eating plants that make them feel unwell

Question 13

State some examples of Mechanical adaptations of plants

Answer 13

Mechanical adaptations of plants

Thorns and hairs deter animals.

Leaves which droop or curl when touched.

Mimicry to trick animals.

Question 14

Explain how Thorns work

Answer 14

Thorns make it unpleasant or painful for large herbivores to eat them

(Thorns are unlikely to deter insects)

Question 15

Give examples of plants where thorns are used as a mechanical adaptation

Answer 15

Brambles
Cacti
Gorse

Question 16

Explain how hairy stems work

Answer 16

Hairy stems and leaves deter insects and larger animals from feeding on them or laying their eggs on the leaves or stems.

Question 17

Give an example of plants where thorns are used as a mechanical adaptation

Answer 17

Lamb’s ears
Some pelargoniums
Poppies

Some plants combine hairs with poisons e.g. nettles

Question 18

Explain how drooping or curling when touched works

Answer 18

When touched, the leaves collapse suddenly, dislodging insects and frightening larger animals

Question 19

Give an example of plants where leaves droop or curl when touched are used as a mechanical adaptation

Answer 19

Mimosa pudica will curl and point leaves to the ground when an insect touches it

Question 20

Explain how mimicry works

Answer 20

Some plants droop to mimic unhealthy plants and this tricks animals into not eating them.

They can also resemble larger insects to scare away any potential threats

Some plants mimic butterfly eggs on their surfaces, so real butterflies do not lay eggs on them to avoid competition with other caterpillars.

Question 21

Give an example of plants where mimicry is used as a mechanical adaptation

Answer 21

Passion flowers have evolved to mimic butterfly eggs on their surfaces, so real butterflies do not lay eggs on them to avoid competition with other caterpillars.

White dead nettle does not sting, but looks very similar to a stinging nettle. Herbivores are less likely to eat white dead nettle as they can easily mistake it for a stinging nettle, protecting the white dead nettle from being eaten.