How does your body defend itself against microbes?

Today we are learning:• How our understanding of

the spread and prevention of disease has developed

• About the natural barriers we have to fight infection

• That we make antibodies and specialised cells in the blood to fight microbes

Keywords:

Hygiene, immunity, vaccination, antibodies.

Starter:

Label the microbes

Extension:

What happens to your body when you catch a cold? Discuss in pairs.

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Virus

A virus is a simple organism which does not completely display ALL the characteristics of living things. It consists of a protein coating and a strand of genes.

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Bacteria

A bacteria is a single celled organism which does not completely have a nucleus. Their genes are found in the chromosomes.

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Fungus

Yeast is a fungus and as can be seen below, it has a more complex structure than the other two types of microbes.

By the end of the lesson you should be able to describe: • how micro-organisms can cause infections and can be passed from one person to another.

• how bias, lack of evidence or misconceptions can give rise to inappropriate theories and the role of scientists in questioning these’.

Learning outcomes

John Snow (1813-1858) was a British physician.

He is considered to be one of the fathers of epidemiology, because of his work in tracing the source of a cholera outbreak in Soho, England, in 1854.

The London cholera epidemic

We know cholera is caused by a bacterium (Vibrio cholerae).Symptoms include chronic diarrhoea, low blood pressure and dehydration.Infected patients can die within 3 hours if left untreated.

In 1854, there was a cholera outbreak in Soho, London.

It had devastating outcomes with over 500 fatalities.

Nearly all families lost at least one member (regardless of socioeconomic class).

People thought that cholera was caused by ‘bad’ air

John Snow did not believe this and he began to collect evidence

John Snow mapped where the cholera cases occurred

• Complete the worksheet including report (15 minutes total)

Your task

By talking to local residents, Snow identified the source of the outbreak as the public water pump on Broad Street.

Snow later used a spot map to illustrate how cases of cholera were centred around the pump.

Snow concluded that all the people infected with cholera had drunk water collected from the Broad Street well.

It was later discovered that a leaking cess pit containing sewage was only 3ft away from the well and was contaminating the water.

Snow's studies of the pattern of the disease were convincing enough to persuade the local council to disable the well pump by removing its handle.

This caused the number of cholera cases to decrease rapidly.

Edward Jenner and vaccination

Many years ago there was a disease called SMALLPOX,

people living in the countryside noticed that

milkmaids never seemed to catch the deadly disease.

This was because they were subjected to another similar

infection caught from the cows they milked (cowpox).

Edward Jenner

Edward Jenner

In 1796 a doctor called Edward Jenner carried out a famous experiment on an

eight year old boy called James Phipps.

Edward Jenner

Jenner took pus from someone with mild cowpox and put it into a cut in the

eight year olds arm.

He never caught smallpox, for many years after that Jenner conducted lots of

experiments to prove that our bodies can become

IMMUNE.

Questions:

• Do you think the experiment that Dr. Jenner did on James was a dangerous one?

• If you were James' parents, would you let Dr. Jenner do the experiment on James? What questions would you ask Dr. Jenner?

• If you were James, now that you are safe from contracting smallpox, would you advise your friends to have the vaccination?

Homework Complete the Jenner and vaccination work sheet

How does your body defend itself?

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Fighting disease

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Fighting disease

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• Explain how white blood cells defend against disease (can use diagrams ) 5 minutes

Your task

How does your body defend itself?Our bodies have many defence mechanisms against invading microbes:

If our skin is cut platelets seal the wound by clotting

The breathing organs produce mucus to cover the lining of these organs and trap the microbes

The skin acts as a barrier

Stomach produces stomach acid

Tears contain an enzyme that kills bacteria

On your outline of the human body, label how we stop micro-organisms getting into our bodies. Here is an example for you.

Ear wax traps them

How does your body defend itself?

End of lesson quiz

Turn to the back of your book and put 1 to 10 in the margin.

The questions will pop up, answer them as quickly as possible.

Quiz questions

1. Name the 3 main types of microbes

2. Which organ uses acid to kill microbes?

3. What do white blood cells make to fight microbes?

4. Name the doctor that experimented with smallpox

5. What does engulf mean?

5 correct LEVEL 5+

4 correct LEVEL 4

2-3 correct LEVEL 3

0-1 correct LEVEL 2

Next lesson…

We are going to look at how we can

kill bacterial.

We need to grow some bacteria to

look at next lesson.

Listen carefully to your instructions

and make sure you wear goggles!