Our Living World 3
Summary Notes
East Lothian Council
Contents
1.
What are microbes? ..............................................................................................2
a.
What parts of a cell are found in microbes? ...................................................2
b. How do microbes reproduce? ..............................................................................3
2. How are diseases spread? ....................................................................................3
a.
How can the spread of disease be prevented? ...............................................3
b. Vaccinations .............................................................................................................3
3. Flu...............................................................................................................................4
4. HIV ............................................................................................................................4
5. HPV ............................................................................................................................4
6. MRSA ........................................................................................................................4
7. Using bacteria to make yoghurt and cheese ....................................................4
8. What can yeast do for us? ...................................................................................4
a.
Microbes and bread making .................................................................................5
b. Immobilising Yeast .................................................................................................5
9. Are Biological Washing Powders Effective? ....................................................5
10.
Designing experiments ......................................................................................5
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1.
What are microbes?
Microbes (sometimes called microorganisms) are all around us. They are in
the air, on our skin and in the food we eat. There are five types of
microbes.
1. Bacteria
2. Viruses
3. Fungi
4. Algae
5. Protozoa
Microbes have many different roles to play in our lives. Some are very
useful while others are harmful.
Microbes are tiny living things which can only be seen with a microscope.
Bacteria can cause diseases such as cholera, sore throats and food
poisoning. Some bacteria are useful, for example they allow us to make
yoghurt and we need them in our gut to keep us healthy.
Viruses are much smaller than bacteria. They are harmful and cause
diseases such as flu, chicken pox and colds.
Fungi include moulds such as those which grow on old bread. Some skin
diseases are caused by fungi, like athletes foot and ringworm. Yeast is a
type of fungus and is used in brewing and baking.
a.What parts of a cell are found in
microbes?
Part of cell Do fungi have Do bacteria
this part?
have this part?
Cell
membrane
Cell wall
Cell nucleus
2
Do viruses
have this
part?
b.
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


Bacteria reproduce by diving in two.
Viruses reproduce in living cells.
Fungi can reproduce by budding (where a parent yeast cell forms a
growth on its surface, which eventually pinches off) or by producing
spores (like seeds - they can be carried on the wind or rain, spreading
the fungus to new places).
Bacteria and fungi need temperature, food, water & time to grow.
The world is not over-run with microbes because conditions are rarely
perfect for them to grow in.
2.




How do microbes reproduce?
How are diseases spread?
Through the air e.g. when someone who has a cold sneezes without
covering his/her mouth.
Through the skin – e.g. touching an infected person can spread
viruses that cause chicken pox and measles.
Through the digestive system e.g. food can be infected by dirty
hands.
Through the reproductive system e.g. HIV can pass from one person
to another during sexual intercourse.
a.How can the spread of disease be
prevented?




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
Wash your hands thoroughly after going to the toilet and before
handling food.
Cook food thoroughly and eat it whilst it’s still hot.
Use a condom when having sexual intercourse.
Cover your nose when you sneeze and your mouth when you cough.
Get immunized.
If you’re sick, stay at home until you’re better.
b.
Vaccinations
Vaccinations involve dead or weakened microbes being injected into the
body. These make the body produce antibodies so that the body’s defences
are ready if the disease ever attacks.
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3.
Flu
Flu is an infectious and common viral illness spread by coughs and sneezes.
It causes a sudden high temperature, headache and general aches and pains,
tiredness and a sore throat. You can also lose your appetite, feel nauseous
and have a cough. It is highly infectious. There is no cure for flu, however
there is a vaccination available that can help to prevent its spread.
4.
HIV
HIV is a virus which attacks the immune system, and weakens your ability to
fight infections and disease. It's most commonly caught by having sexual
intercourse without a condom. There is no cure for HIV.
5.
HPV
The human papilloma virus (HPV) is the name given to a family of viruses.
Some types of HPV can cause warts or verrucas. Other types are associated
with cervical cancer. The HPV virus is very common and is easily spread by
sexual activity. All girls aged 11 to 13 are offered HPV vaccination as part
of the NHS childhood vaccination programme in Scotland. The vaccine
protects against cervical cancer.
6.
MRSA
MRSA is a type of bacterial infection that is resistant to a number of
widely used antibiotics. This means it can be more difficult to treat than
other bacterial infections. MRSA infections are more common in people who
are in hospital or nursing homes. It enters the body through an open wound.
7.
Using bacteria to make yoghurt and
cheese
Bacteria are used to make yoghurt and cheese. They thicken milk and cause
it to sour. Different sorts of microbes make different sorts of cheese.
8.
What can yeast do for us?
Yeast is used in the brewing industry to make beer and wine. The name of
this process is fermentation. Fermentation is carried out by microorganisms to produce energy for their growth and reproduction. Alcohol and
carbon dioxide are produced if no oxygen is present.
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a.Microbes and bread making
Bakers add yeast to dough to make it rise. Yeast feeds on sugar in the
dough and produces bubbles of carbon dioxide. This process is called
fermentation. The bubbles makes the dough swell. During the baking of the
bread, the yeast is killed and fermentation stops.
b.
Immobilising Yeast
Yeast can be immobilised in jelly beads. This technique is used in industry
because it is easier to separate the yeast from the end product and the
yeast can be reused. Immobilised yeast is used to make Kefir, which is a
slightly alcoholic milk drink which originated in Eastern European countries.
9.
Are Biological Washing Powders
Effective?
Enzymes are used in biological washing powders. They break down stains so
that the stain is removed. Non-biological washing powders do not have
enzymes in them, but are kinder to skin.
10.
Designing experiments
In an experiment, the independent variable is the thing you are
investigating e.g. in an experiment investigating the effect of exercise on
heart rate, the independent variable is exercise. You usually only have one
independent variable in an experiment, so you can be sure of the effect its
having.
The dependent variable is the thing you measure in an experiment e.g. in an
experiment investigating the effect of exercise on heart rate, the
dependent variable is heart rate.
A control is a copy of the experiment where you don’t change the
independent variable. For example, in an experiment investigating the
effect of exercise on heart rate, a control could be doing no exercise. A
control makes sure that it’s the independent variable that causing the
effect on the dependent variable.
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