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KS3 Biology. 8C Microbes and Disease. Contents. 8C Microbes and Disease. What are microbes?. Uses of microbes. How microbes cause disease. Fighting disease. Summary activities. What are microbes?. Microbes are very small living things and are sometimes called

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Ks3 biology l.jpg

KS3 Biology

8C Microbes

and Disease


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Contents

8C Microbes and Disease

What are microbes?

Uses of microbes

How microbes cause disease

Fighting disease

Summary activities


What are microbes l.jpg

What are microbes?

Microbes are very small living things and are sometimes called

micro-organisms.

Microbes are so tiny that they cannot be seen with the naked eye. They can only be seen using a microscope.

How many different microbes can you name?


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Different types of microbes

There are three types of microbes:

microbes

bacteria

viruses

fungi


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Bacteria fact file

Bacteria e.g. Salmonella and Streptococcus

size:1/1000 mm

shape: Bacteria can be spherical, rod-shaped or comma-shaped.

structure: Bacteria are single-celled organisms, which do not completely have a nucleus.

Some cause disease, but many

are useful.

reproduction: Bacteria reproduce very quickly. Two can very quickly become four, then eight and so on.


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Bacterium structure


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Viruses fact file

Viruses e.g. flu virus and HIV (the AIDS virus)

size: 1/1,000,000 mm

shape: Viruses have regular and geometric shapes.

structure: A virus is a simple organism which does not display ALL the characteristics of living things.They are made up of a protein coating and some genetic material.

reproduction: Viruses can only grow and reproduce within other living things.


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Virus structure


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Fungi fact file

Fungi e.g. Penicillium and yeast

size: Some fungi can actually be seen with the naked eye, others are slightly bigger than bacterial cells.

shape: Fungi come in many different shapes.

structure: Fungi have the

most complex structures of

all the microbes. They feed

off other living things.


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Fungi (yeast) structure


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Contents

8C Microbes and Disease

What are microbes?

Uses of microbes

How microbes cause disease

Fighting disease

Summary activities


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Using microbes – bacteria and fungi

Microbes have many uses that are based on the fact that microbes can be grown.

  • Bacteria grow in milk to make it ‘go off’.

  • This type of bacterial growth is used to make milk into yoghurt.

  • Cheese is another product that is made from milk.

Fungi can also be used to make food. The meat substitute Quorn is a protein produced using fungi.


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Using microbes – yeast

Yeast is a type of fungus and carries out respiration.

The respiration of this microbe can be used in different ways in baking bread and in brewing.

The aerobicrespiration of yeast is used to make bread rise.

Yeast uses the sugar in bread dough to carry out aerobic respiration:

energy

glucose

water

oxygen

carbon

dioxide

What gas produced by the aerobic respiration of yeast causes bread to rise?


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Using microbes – yeast

The anaerobicrespiration of yeast is used to make beer and wine.

In this case, the yeast respires without oxygen and produces alcohol (ethanol). This process is known as fermentation.

Yeast converts the sugar into alcohol by anaerobic respiration:

energy

glucose

ethanol

carbon

dioxide

How do brewersmake sure that yeast respire without oxygen?


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Contents

8C Microbes and Disease

What are microbes?

Uses of microbes

How microbes cause disease

Fighting disease

Summary activities


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Microbes can cause disease

The diseases caused by microbes and their severity depend on the type of microbe.

viruses

bacteria

fungi

influenza (flu)

food poisoning

fungal sinusitis

mumps

sore throats

athlete’s foot

chickenpox

tuberculosis (TB)

Onychomycosis

(causes discoloured toe nails)

smallpox

tetanus

polio

cholera

rabies

typhoid

German measles

whooping cough

viral

meningitis

bacterial

meningitis


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Which type of microbe?


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How do microbes enter the body?

eyes

ears

mouth

nose

skin

cuts

genitals

Microbes can enter the body in many different places.

How are the diseases caused by microbes spread?


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How are microbes spread?

1. Transmission by air

A cough or a sneeze can release millions of microbes into the air which can then infect somebody else.

2. Transmission by water

Dirty water can transmit many diseases, e.g. cholera, which can be transmitted by drinking.

The spreading of microbes and disease is known as transmission.


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How are microbes spread?

3. Transmission by animals

An animal can carry a microbe from one place to another, e.g. a mosquito which spreads the malaria parasite.

4. Transmission by contact

Many microbes can be exchanged from one person to another by direct or indirect contact:

  • direct contact by hand;

  • indirect contact, e.g. by walking on a

  • wet floor already contaminated by

  • someone else who has athlete’s foot;

  • sexual contact.


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How are microbes spread?

4. Transmission by contact

There are other forms of indirect contact, e.g. the transmission of microbes from mother to unborn child.

  • Transmission through the placenta

If the mother develops the HIV/Aids infection, it can be passed on to the unborn child through the placenta.

  • Transmission via breastfeeding

If a child is being breastfed, he or she can also pick up microbes from the mother via the mother’s milk.


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How is the spread of disease stopped?

Chemicals called antibiotics can be used to treat bacterial infections.

People can be immunized against some diseases by the injection of a vaccine.

The spread of disease can be prevented by making sure that good hygiene is used in key places such as bathrooms and kitchens.


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Contents

8C Microbes and Disease

What are microbes?

Uses of microbes

How microbes cause disease

Fighting disease

Summary activities


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Fighting microbes

How does the body fight off microbes that cause disease?


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What do white blood cells do?

white blood cell

antigen

antibody

The human body has a number of natural defences against microbes. Noses are hairy inside to trap microbes!

The body also produces white blood cells to help defend it from microbes.

Some white blood cells can destroy microbes by engulfing them.

Some white blood cells are able to produce chemicals called antibodies. These pairing with matching antigens on the surfaces of microbes and so help the white blood cells to engulf microbes.


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White blood cell engulfs microbe – animation


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White blood cell and antibodies – animation


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Contents

8C Microbes and Disease

What are microbes?

Uses of microbes

How microbes cause disease

Fighting disease

Summary activities


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Glossary

  • antibiotics – Chemicals prescribed as medicine to kill bacteria inside the body.

  • antibodies – Chemicals produced by white blood cells to fight microbes that cause disease.

  • bacteria –The type of microbes that are single-celled organisms.

  • fungi –The type of microbes that feed off other living things.

  • immune – Resistance to infection caused by a microbe.

  • microbe –A very small living thing.

  • transmission –The spread of a disease from person to person.

  • viruses –The type of microbes that can only grow and reproduce within other living things.


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Anagrams


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Multiple-choice quiz


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