Edexcel GCSE Biology 1BI0
Key Concepts in Biology
Cells and Control
Genetics
Natural Selection and Genetic Modification
Health, Disease and the Development of Medicines
Plant Structures and Their Functions
Animal Coordination, Control and Homeostasis
Exchange and Transport in Animals
Ecosystems and Material Cycles
Health, Disease and the Development of Medicines
How plants defend themselves and how plant disease is detected
- 3 things to know
- Paper 1
Overview
Physical plant defences such as the waxy cuticle, cell wall, bark and layers of dead cells, chemical defences including quinine, salicylic acid and caffeine and their value in medicine, and diagnosing plant disease by ruling out environmental causes, studying distribution and symptoms, and using DNA analysis and antibody test kits.
What you need to know
Answer each one before you reveal it.
Explain how the cell wall protects a plant cell from a pathogen.
Explain why damage to the bark of a tree increases the chance of infection.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Name two physical barriers that protect a plant from pathogens.
Model answer
The waxy leaf cuticle and the cell wall.
- 2
Describe how the waxy cuticle of a leaf defends the plant.
Model answer
It forms a waterproof layer over the leaf surface that stops pathogens reaching the cells beneath.
- 3
Explain how the cell wall protects a plant cell from a pathogen.
Model answer
The cellulose wall is a tough barrier that a pathogen must break down before it can reach the cell contents.
- 4
Explain why damage to the bark of a tree increases the chance of infection.
Model answer
Bark is a physical barrier, so a wound gives pathogens direct access to the living tissue underneath.
- 5
Describe how a layer of dead cells around a stem helps to defend a plant.
Model answer
It forms a tough covering that pests and pathogens cannot easily penetrate, and it falls away carrying pathogens with it.
- 6
Explain how a physical barrier in a plant differs from a chemical defence.
Model answer
A physical barrier blocks pathogens from getting in, while a chemical defence kills or deters them once they arrive.
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