Microorganisms, Disease and Health

The tiny life that makes us ill

Microorganisms are living things far too small to see without a microscope, and they include bacteria, viruses and fungi. Most are harmless or even useful, but some, called pathogens, cause disease. A disease you can catch and pass on, because it is caused by a pathogen, is a communicable disease, while one that cannot spread, such as many heart conditions, is non-communicable. Your body is not defenceless: it has barriers that keep most pathogens out, white blood cells that hunt down any that get in, and a memory that makes you faster to fight the same pathogen again. This module covers microorganisms, how disease spreads, how the body defends itself, and how antibiotics, vaccination and hygiene help.

Disease words

Learn these five terms before you study disease and defence.

Match each microbe or defence to its role

Communicable against non-communicable

Diseases fall into two big groups, told apart by whether a pathogen causes them.

Which disease can spread?

A disease is passed from one person to another through coughs and sneezes. What kind of disease must it be?

• A communicable disease
• A non-communicable disease
• An inherited condition only
• Not a disease at all

How antibiotic resistance grows

Antibiotics are medicines that kill bacteria, but they do nothing against viruses, so they cannot cure a cold. There is a second reason to use them carefully. Whenever antibiotics are used, a few bacteria may happen to survive, and those survivors can pass on their resistance as they reproduce. Over time, if antibiotics are overused or a course is stopped early, resistant bacteria spread and the medicine stops working for everyone. That is why doctors prescribe antibiotics only when they are truly needed, and why you should always finish the whole course even once you feel better. Protecting antibiotics is a shared responsibility, because a resistant strain that starts in one person can reach many.

Pick the true facts about disease

Select every statement about disease and defence that is true.

• A pathogen is a microorganism that causes disease
• White blood cells help defend the body
• Antibiotics kill bacteria but not viruses
• Every disease can spread from person to person
• A vaccine gives no protection against disease at all

Order how the body fights an infection

Put the steps of the body fighting an infection in the correct order.

• A pathogen enters the body
• White blood cells detect it
• White blood cells make antibodies
• The pathogen is destroyed
• Memory cells give faster protection next time

Complete the disease facts

A microorganism that causes disease is a _____. A disease that can spread from person to person is _____. The parts of the body that defend it against pathogens make up the _____ system. A medicine that kills bacteria but not viruses is an _____.

A castle under siege

Think of a walled castle defending itself. The high walls and locked gates stop most attackers ever getting in, just as the skin and the acid in the stomach turn away most invaders. If a few attackers do slip through, soldiers inside rush to surround them, and archers who have faced this enemy before know exactly where to aim. The body works in the same layered way: an outer barrier first, then defenders that hunt down anything which breaks in, and a memory of past attackers so the next assault is beaten faster. No single wall does the whole job. It is the layers working together that keep the castle standing, and it is the same teamwork of defences that keeps you well.

Tap the body defences

Tap every item below that is one of the body defences against pathogens.

• the skin as a barrier
• acid in the stomach
• white blood cells
• the colour of your eyes

Work out the bacteria number

One bacterium divides into two every twenty minutes. Starting from a single bacterium, how many bacteria are there after three divisions?

Handle the health situation

Read each situation and choose the best answer.

• You have a cold, which is caused by a virus. Will antibiotics cure it?
• A doctor prescribes antibiotics for a bacterial infection. What should you do?
• How can you help avoid spreading a communicable disease?

Build a disease point

Choose the word for each gap to complete one accurate point about disease and defence.

Explain disease and how the body defends itself

A friend does not understand how we catch diseases and how our bodies fight them. Explain microorganisms, disease and the body defences clearly.

• Explain what a microorganism and a pathogen are
• Explain the difference between communicable and non-communicable disease
• Explain how the body defends itself against pathogens
• Explain what antibiotics do and why finishing the course matters
• Explain how vaccination and good hygiene help