3.1.1

Spreading Disease

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Pathogens and Infections

Infections are caused whenever a foreign pathogen invades an organism (animal or plant). There are four main types of pathogen:

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Viruses

  • Viruses are tiny, non-living (do not contain cells) particles that can reproduce rapidly within the body.
  • They invade host cells and use them to make new virus particles.
  • Once the new viruses are made, they cause the cells to burst.
  • The cell damage makes us feel ill.
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Bacteria

  • Bacteria are small living cells that either damage cells directly or by producing toxins (poisons).
  • Bacteria can reproduce rapidly in the appropriate conditions: warm, moist areas with a good supply of oxygen.
  • The toxins released by bacteria can damage cells and tissues, making us feel ill.
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Fungi

  • Some fungi are single-celled organisms that have a body made up of hyphae (thread-like structures).
  • The hyphae are able to grow and penetrate tissues, such as human skin or the surface of plants.
  • The hyphae produce spores that can spread to other plants and animals.
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Protists

  • Protists are single-celled eukaryotic organisms (they have a nucleus).
  • Many are parasites, meaning that they live on or inside other organisms.
  • They are often transferred to the host organism by a vector, such as an insect or mosquito.
  • They make us feel ill by damaging our tissues.

Jump to other topics

1Cell Biology

1.1What's in Cells?

1.2Cell Division

1.3Transport in Cells

2Organisation

2.1Principles of Organisation

2.2Enzymes

2.3Circulatory System

2.4Non-Communicable Diseases

2.5Plant Tissues, Organs & Systems

3Infection & Response

4Bioenergetics

5Homeostasis & Response

5.1Homeostasis

5.2The Human Nervous System

5.3Hormonal Coordination in Humans

5.4Plant Hormones

6Inheritance, Variation & Evolution

7Ecology

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