Non-specific defences

  • Created by: A-ha
  • Created on: 18-11-19 18:38

Key words

Non-specific defences- defences that are always present

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Non-specific defences in humansPHYSICAL

1) Physical

Respiratory tract

  • Lined with mucus
  • Mucus traps particles 
  • Cilia wafts the mucus up to the back of the throat to be swallowed


  • Barrier


  • Clot blood
  • Blood clotting stops you from loosing too much blood and prevents microorganisms from entering the blood
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Non-specific defences in humansCHEMICAL

2) Chemical


  • enzyme called lysozyme found in tears
  • It breaks down bacteria on eyes surface


  • Contains molecules which kill pathogens


  • Contains hydrochloric acid which kills pathogens
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Non-specific defences in humansMICROBIAL

3) Microbial


  • Pathogens compete with bacteria which naturally lives in the gut, in order to survive
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Plants Physical Defences

Waxy cuticle

  • Found on leaves
  • Waterproof barrier
  • Reduces risk of infection form pathogens transferred in water as it prevents water form collecting on the leaf

Cell walls

  • Made from celluose
  • Physical barrier against pathogens
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Plants Simple Immune System

Produce antimicrobial substances

  • Phytoalexins may be produced, this disrupts the cell structure of fungi and bacteria
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Why plants' defences against pathogens are importa

Strart of food chain

  • Ability to defend themselves helps out other organisms

Example: Damage to crops can threaten human food security

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