Microorganisms and Disease
Pathogens cause infectious diseases.
About this topic
Pathogens are microorganisms causing infectious disease: bacteria (cholera, TB), viruses (flu, HIV), fungi (athlete's foot) and protists (malaria). They spread through direct contact, air droplets, contaminated food or water, and vectors such as mosquitoes.
Defences include physical barriers (skin, mucus, stomach acid), white blood cells that engulf pathogens or make antibodies, and vaccines. Pathogens cause symptoms by damaging cells or releasing toxins. Incubation is the time between infection and symptoms, during which people may spread the disease without knowing.
Louis Pasteur and Robert Koch established the germ theory in the nineteenth century, replacing ideas of bad air. John Snow traced a cholera outbreak in London in 1854 to a water pump, showing how identifying the source can stop disease. Hand washing, clean water and sewage treatment have saved millions of lives.
Antibiotics treat bacterial infections, not viral ones. Resistance is a growing threat. Students often say that cold weather causes colds; in fact, viruses cause them, though crowding indoors helps spread. Also, not all microorganisms are pathogens; most are harmless.
Key ideas
- Bacteria, viruses, fungi, protists
- Spread by air, water, contact, vectors
- Hygiene reduces spread
Quick check
Use cases: where Microorganisms and Disease helps
- Homework: review the key idea behind Microorganisms and Disease before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Microorganisms and Disease without notes.
- Visual learning: play with the interactive lab to see how Microorganisms and Disease changes when you adjust its inputs.
- Teaching a friend: explain Microorganisms and Disease in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Microorganisms and Disease?
Pathogens cause infectious diseases.
What will I learn in Microorganisms and Disease?
Bacteria, viruses, fungi, protists. Spread by air, water, contact, vectors. Hygiene reduces spread.
Is Microorganisms and Disease part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Microorganisms and Disease lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Microorganisms and Disease?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.