Transcript How does your body defend itself against microbes?

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.
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.
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Learning outcomes
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’.
The London cholera epidemic
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.
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
Your task
• Complete the worksheet including report
(15 minutes total)
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?
Fighting disease
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Fighting disease
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Your task
• Explain how white blood cells defend
against disease (can use diagrams ) 5
minutes (page 87 spectrum biology)
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How does your body defend itself?
Our bodies have many defence mechanisms against invading
microbes:
Tears contain an
enzyme that kills
The skin acts
bacteria
as a barrier
Stomach produces
stomach acid
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
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!