AQA Biology 4.3.1.1 · 4.3.1.6
Communicable diseases and defences
Pathogens spread from host to host. Follow one in, switch off a defence, and see what stops it next.
Triple Science · Higher tier
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Germs everywhere.
Germs are on door handles, phones and your own hands. You touch thousands of them every day.
If you had to guess, would a germ get into your body more easily through unbroken skin, or through a cut?
Pathogens · how they spread
Four kinds of pathogen, a few ways in.
Pathogens are microorganisms that cause infectious disease: viruses, bacteria, protists and fungi. They may infect plants or animals. Bacteria and viruses reproduce rapidly inside the body. Bacteria may produce toxins that damage tissues; viruses live and reproduce inside cells, causing cell damage.
Pick a route of spread, then see what breaks it.
Pick a route.
Vaccination stops many diseases spreading at all: in Vaccination. The named diseases are in Viral, Bacterial and Fungal and protist diseases.
Non-specific defences
Keep them out.
Most pathogens are stopped before they get into the body. Pick how a pathogen arrives, then switch that defence off and see how far it gets.
The nose traps particles that may contain pathogens. In the trachea and bronchi, mucus traps pathogens and cilia move the mucus up to the throat, where it is swallowed.
The immune system · white blood cells
If a pathogen gets in.
If a pathogen enters the body, the immune system tries to destroy it. White blood cells do this in three ways. Pick each one.
Phagocytes engulf pathogens and digest them. They attack any pathogen they meet.
Some white blood cells stay in the blood as memory cells, so if the same pathogen comes back the right antibodies are made quickly: more in Vaccination.
Think again · who makes antibodies?
“Phagocytes make antibodies.”
Your call
ChooseWhich white blood cells make antibodies?
Sort
Barrier or white blood cell?
Place each defence.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Describe
- Each defence, and what it does to the pathogen.
- Explain
- How a defence stops the pathogen, link by link.
- Give
- One way to break a route of spread.
Key fact
Barriers keep most pathogens out. White blood cells destroy those that get in: phagocytosis, antibodies and antitoxins.
Key note · AQA 4.3.1.1, 4.3.1.6
Communicable diseases and defences
- Pathogens are microorganisms that cause infectious disease: viruses, bacteria, protists and fungi. They infect plants or animals.
- They spread by air, water, direct contact, or a vector. Break the route: isolate, treat water, hygiene and condoms, control vectors.
- Barriers: skin; the nose; mucus and cilia in the trachea and bronchi; acid in the stomach.
- White blood cells: phagocytosis; antibody production; antitoxin production.
Photograph this card. Tomorrow, cover it and say each line first.
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Not sure which white blood cell does what?
Drawings are schematic, not to scale.