as level biology - pathogens
Post on 25-May-2015
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AS Level BiologyChapter 1.1 - Pathogens
What are they?
What are pathogens?
• Pathogens are microorganisms that cause diseases. There are four kinds of pathogens:
Bacteria, e.g. salmonella and cholera.Viruses, e.g. influenza and AIDS.Fungi, e.g. athlete’s foot and pneumocystis.Protozoa, e.g. malaria and dysentery.
What is disease?
• Diseases are not one thing, but they are compromised of certain symptoms. Some of the symptoms of influenza are sneezing, coughing, and a high temperature.
To be a pathogen, it must:
• Gain entry to the host.• Colonise the host’s tissues.• Resist the host’s defences.• Damage the host’s tissues.
How do pathogens enter the body?
• The gas-exchange system – you can breathe in air droplets that contain diseases such as influenza and tuberculosis, which means you can be diagnosed with these diseases.
• The digestive system – diseases like cholera are water-borne diseases that affect the digestive system (loss of water from the large intestines)
• Through cuts and broken skin – HIV/AIDS and hepatitis
How does the body prevent pathogens from entering the body?
• A mucous layer that covers the exchange surfaces and forms a thick barrier so pathogens can’t penetrate it.
• The production of enzymes to break down the pathogens.
• The production of stomach acid to kill the pathogens.
How do pathogens cause disease?
• By damaging the host’s tissues – e.g. influenza
• By producing toxins – e.g. cholera
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