Spreading Disease
Biology: AQA GCSE Higher, topic 3.1.1
Pathogens and Infections
Infections are caused whenever a foreign pathogen invades an organism (animal or plant). There are four main types of pathogen:
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.
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.
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.
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.
Test yourself on Spreading Disease
Why does a body cell often burst after a virus has reproduced inside it?
How does the way fungi spread to a new host differ from the way viruses spread?