MODULE mod7A mod7B mod7C mod7D mod7E mod7F mod7G mod7H mod7I mod7J mod7K mod7L mod8A mod8B mod8C mod8D mod8E mod8F mod8G mod8H mod8I mod8J mod8K mod8L mod9A mod9B mod9C mod9D mod9E mod9F mod9G mod9H mod9I mod9J mod9K mod9L 8ca1
8Ca1 Microbe quest
Name _____________________________ Class ____________
1 a From the following list, circle the things that are micro-organisms.
elephants yeast humans earthworms daffodils
bacteria viruses
b Write down the list again, in order of size. Start with the biggest one.
1 (biggest) _____________________ 5 _________________________
2 _________________________ 6 _________________________
3 _________________________ 7 (smallest) _________________
4 _________________________
2 a Here are some drawings of different bacteria. Use the key to identify which is which. Write down the correct name underneath each picture (you do not need to remember the names).
i____________ ii____________ iii____________ iv____________
1
Each cell is ball-shaped
go to 2
Each cell is not ball-shaped
go to 5
2
Bacteria are not joined together
Coccus
Bacteria are joined together in groups
go to 3
3
There are two bacteria in each group
Diplococcus
There are more than two bacteria in each group
go to 4
4
Bacteria are grouped in chains
Streptococcus
Bacteria are grouped in bunches
Staphylococcus
5
The cell has many 'tails' coming out of it
Salmonella
The cell has one 'tail' coming out of it
go to 6
6
The cell looks like a spiral (cork-screw shaped)
Spirillum
The cell is comma shaped
Vibrio
b Draw a picture of what you think a Vibrio looks like.
[ knowledge, observing ]
8Ca2 Which microbe?
1 The pictures show a virus, a bacterium and a yeast cell. Which one is which?
a
b c Drawings not to scale
2 Look at the pictures in question 1 again.
a In real life, which one is the smallest?
b In real life, which one is the biggest?
Read the passage below and then answer the questions which follow.
Very small living things are called microbes or micro-organisms; 'organisms' because they are living things, 'micro-' because they are very small. All living things should be able to carry out the seven life processes. However, viruses are a bit of an exception to this rule and some scientists do not think that they are really living. Of the seven life processes they can only reproduce and even then they cannot do this on their own - they need to be inside another living cell. However, most people think of viruses as micro-organisms because they are very small and, like all living things, contain genes.
3 a What is the proper name for a 'living thing'?
b What is the other name for 'micro-organisms'?
c What piece of equipment do you need to use to see micro-organisms?
d List the seven life processes.
e Which of these life processes can viruses not do at all?
f Which of these life processes can viruses do when inside another living cell?
g If they are not really living, why do people tend to call viruses 'micro-organisms'?
[ knowledge, literacy ]
8Ca3 Microbial world
Microbes come in many shapes and sizes. The pictures below show some examples with a scale given for each. 1µm (micrometre) = 0.001 mm, 1 nm (nanometre) = 0.000001 mm.
1 a Design a table to show the lengths (or diameters if they are spherical) of each of the microbes. Put the organisms in order starting with the longest.
b What do you think is unusual about Thiomargarita namibiensis?
2 a Copy the drawings below and fill in the missing labels.
b What feature of this bacterium allows it to move?
c Why is it not really correct to call a virus a micro-organism?
[ knowledge, numeracy ]
8Ca4 Protoctists
The first person to describe protoctists was a Dutch cloth salesman called Antoni van Leeuwenhoek (1632-1723). He became very good at making lenses which he used to inspect the fibres in the cloth he bought and sold. He also made microscopes and in 1674 he discovered tiny one-celled moving organisms in water which he called animacules (tiny animals).
Today we consider these 'animacules' as part of the protoctist kingdom. This kingdom contains many very different organisms - everything from the smallest algae (0.01 mm long) to huge giant kelp seaweeds (up to 65 m long). These organisms are classified as protoctists because they do not fit very well into any other group. Like plants, fungi and animals, protoctists have nuclei in their cells, but unlike these other groups, their cells do not group together to form different tissues (all their cells are very much the same).
Many protoctists are one-celled or unicellular. One is called Euglena which has some features that you would expect to find in an animal cell and others which you would expect to find in a plant cell.
1 a Who first discovered small protoctists?
b Why do you think he called them 'animacules' and not 'planticules'?
2 a Name one unicellular protoctist.
b What do you think the word multicellular means?
c Name one multicellular protoctist.
3 a Write down one difference between a unicellular protoctist and a bacterium.
b Write down one difference between any protoctist and a plant or an animal.
4 List the features of Euglena:
a that are the same as both animal and plant cells
b that are the same as plant cells
c that are the same as a whole animal (e.g. a rabbit).
5 Until 1862 all organisms were classified as either plants or animals. A German biologist called Ernst Haeckel (1834-1919) first divided protoctists (or protists as he called them) into a different kingdom. Why do you think he did this?
8Cb1 Rising dough 1
Which temperature is best for dough to rise?
You are going to investigate how temperature affects the rising of bread dough. Yeast is a microbe which is added to bread dough. When the yeast cells respire they produce carbon dioxide which makes the dough rise. Respiration is a chemical reaction that happens in all living cells including yeast cells.
Prediction
1 Do you think the dough will rise furthest in cold or warm conditions?
2 Why do you think this?
Apparatus
- Sugar - Dried yeast
- Bread flour - Water
- 3 measuring cylinders - Large beaker
- Tablespoon - Thermometer
- Stirring rod
Do not try to eat any of your dough.
Method
1 Measure out 5 g of sugar, 3.5 g of yeast and 100 g of bread flour. Add them all to a large beaker.
2 Now measure out 65 cm3 of water.
3 Pour the water, a little bit at a time, into the beaker. Each time you have added some water, stir the mixture using the spoon.
4 Keep stirring until the mixture is a smooth paste. Now very slowly pour or spoon 20 cm3 of the mixture into a measuring cylinder. Put another 20 cm3 of mixture into each of the other two measuring cylinders. Any bits which get stuck to the side you can push down to the bottom with the stirring rod.
5 Label the cylinders to show the different temperatures they will be placed at - 'cold', 'cool' and 'warm'.
6 Record the volume of dough in each cylinder.
7 Put the cylinders in the different places for the different temperatures. Use a thermometer to measure the exact temperature in each area.
8 Leave them for 1 hour.
9 Now read the new volume of the dough in each cylinder.
Recording your results
3 Record your results in a table like this:
Temperature of the area the dough was left in
Volume of dough at the start of the experiment (cm3)
Volume of dough at the end of the experiment (cm3)
Increase in the volume of the dough (cm3)
cold ( °C)
cool ( °C)
warm ( °C)
Considering your results/conclusions
4 Draw a bar chart to show the increase in volume of the dough at each temperature.
5 a Which was the best temperature for the rising of dough?
b How do you know this?
6 a Why does the dough rise?
b Why do you think it rises faster at some temperatures than others?
Evaluation
7 a Which was the most tricky part of the experiment?
b How do you think this might have affected your results?
c Try to think of a way of improving this part of the experiment.
8 How would you show that the bread needs yeast to make it rise?
[ knowledge, observing, presenting, considering, evaluating ]
8Cb2 Rising dough 2
What factors affect the speed at which dough rises?
Bread dough can be made by mixing together 5 g of sugar, 3.5 g of yeast, 100 g of bread flour and 65 cm3 of water. When kept in a warm place, the bread dough rises.
Planning
Do your planning with the others in your group. You will need to discuss the following things.
1 Variables: what could you change that might affect how quickly the bread dough rises? Write down all the variables you can think of.
2 Choose one or two variables to test.
a How will you test them?
b What will you measure?
c What range of measurements will you use? (e.g. how long will you run the experiment for?)
d What apparatus will you need and how will you set it up?
e How many measurements will you make?
3 Fair test: you should only change one variable at a time. Write down all the factors you will keep the same.
4 How will you make this a safe investigation?
5 Now discuss your plan with all the other groups in your class. Agree on one method.
6 Prediction: write down what you think will happen. Use your scientific knowledge to explain why you think this will happen. You will need to know about yeast and respiration.
7 You are going to gather all the results from all the groups in your class.
a How many results will you have altogether?
b Do you think this will be enough to be confident that what you find out will be true?
8 Get the results from other groups and draw a table of all the results.
9 Draw a chart or graph to show the results.
10 Does what happened match your prediction? If not, write down what is different.
11 a Use your chart or graph to identify a trend (pattern) in the results.
b Why did you get this trend? Explain what was happening.
12 Are there any results that do not fit the overall pattern? Which ones?
13 Why was it important that everyone in the class used the same method?
14 How confident are you that the trend (pattern) in your results is really there? Why?
15 a Which was the most tricky part of the experiment?
16 How would you show that the bread needs yeast to make it rise?
8Cb3 Making bread
The diagrams below show how bread is made. Look at them carefully and then answer the questions.
1 a What is dough made out of?
b What is 'kneading'?
c Why is the dough 'kneaded'?
2 What does the 'divider' do?
3 a What sort of microbe is yeast?
b What does the yeast use the sugar for?
c Copy and complete this word equation for this process.
glucose + ______________ → ______________ ______________ + water (+ energy)
4 One baker wants to make bread which is long and thin. Which two pieces of equipment would the baker need to change the shape of?
5 a Where is the bread baked?
b What do you think happens to the yeast when bread is baked?
[ literacy, knowledge ]
8Cb4 Yeast respiration
An experiment was done to find out the best temperature for yeast to respire. The yeast were grown in a sugar solution in a flat dish to allow them to get a lot of oxygen from the air. If there is too little oxygen, the yeast respire differently and do not produce so much carbon dioxide. The carbon dioxide they produced in each hour was collected and the results are shown below.
Some people enjoy kneading bread. They find it 'therapeutic', which means that it makes them feel better.
Time (hours)
Volume of gas collected (cm3)
At 25 °C
At 30 °C
10
11
16
34
30
90
70
200
120
400
220
800
1 Plot these results on a graph.
2 Yeast is used in bread-making to make the dough rise. Which of the two temperatures do you think would be better for getting dough to rise? Explain your answer.
3 a What sort of respiration do you think is happening in this experiment?
b How do bread-makers try to make sure that this sort of respiration happens in their dough?
c Write down a word equation for this type of respiration.
4 Why do you think more carbon dioxide was produced towards the end of the experiment than at the beginning of the experiment?
5 Do you think there is enough evidence from this experiment to say what temperature would be best for dough to rise? Explain your answer.
6 a Another type of respiration can happen in yeast. What is it called?
b Write down a word equation for this type of respiration.
c Why do you think this type of respiration is useful for making alcoholic drinks?
d Sketch a curve on the graph to show how much carbon dioxide would be produced if this type of respiration was occurring and the temperature was 25 °C.
[ knowledge, numeracy, evaluating ]
8Cb5 Yeast populations
To make wine, grape juice and sugar are mixed together, and yeast are added to ferment it. A wine maker took samples of his wine as it was fermenting and counted the number of yeast cells in each sample. The graph shows the winemaker's results.
1 a What is fermentation? Use the word 'respiration' in your answer.
b Copy and complete this word equation for fermentation:
glucose → ______ ________ + ________ (+ ________ )
2 How many yeast cells were in the sample that the winemaker took after:
a 7 days b 2 days?
3 How many yeast cells would the winemaker expect the find in a sample taken at:
a 4.5 days b 9.5 days?
4 The rate of growth of a population is the speed at which it increases. For this experiment you could measure it in units such as 'increase in number of yeast cells/day'. What was the rate of growth of the yeast population between days 4 and 7?
5 How do you think the rate of growth of the population might have been affected if:
a the wine was kept at a lower temperature
b more sugar was added to the wine before it was allowed to ferment?
6 a After seven days the rate of growth of the population started to slow down. Give one reason for this.
b What is a factor called that causes a population to stop increasing?
7 After day 10, the population of living cells started to decrease. Why do you think this might have happened?
8Cb6 Populations
The graphs show the growth of two populations - yeast and humans. Graphs like these are called growth curves.
Population graphs often show some common features. They often start with a lag phase which is when the organisms are adjusting to their surroundings and not reproducing very much. The log phase occurs when conditions for reproduction are good and so the size of the population increases rapidly. The stationary phase occurs when things necessary for the organisms are in short supply (e.g. food, oxygen). The death rate is the same as the reproduction rate and so the population stays the same size. In the death phase, things necessary for the organisms run out or something in the surroundings starts killing the organisms. The death rate is high and so the population decreases.
1 Write down the day numbers that correspond to each of the four phases of the growth curve for the yeast.
2 a In the stationary phase, why does the population remain the same?
b Give one example of a limiting factor that might affect the growth of a yeast population in this phase.
3 In the death phase, some microbes are poisoned by the chemicals that they produce as a result of their respiration. Suggest one chemical that might cause the yeast population to enter the death phase.
4 a Which phases are absent in the human population growth curve?
b Which phase is the human population growth curve in at the moment?
5 a Today, people live longer. How does this affect the human population?
b Suggest two reasons why people live longer today.
c Write down two limiting factors for human population growth.
d What do you think will happen if the human population continues to grow at its present rate?
[ knowledge, literacy, numeracy ]
8Cc1 Growing bacteria
- Agar plate - Bunsen burner
- Wire loop - Agar slope of bacteria
- Heatproof mat - Incubator at 20-25 °C
- Sticky tape
Do not open the agar plate dish once it has been taped. Be very careful with hot wire loops.
1 Take your wire loop and pass it through the Bunsen flame until it is red hot along its length.
2 Open the bottle with the bacterial culture inside. Pass the neck of the bottle through the Bunsen flame.
3 Using the wire loop remove a small amount of bacteria from the agar slope.
4 Take out the loop, replace the bottle, replace the cap and open the agar plate.
5 Gently make three lines across the agar on one side of the agar plate.
6 Close the agar plate and pass the wire loop through the flame again, as in step 1. Allow the loop to cool in the air.
7 Open the agar plate. Now gently streak the loop across the first three lines that you made, like this:
8 Repeat steps 6 and 7 once more to make this sort of pattern:
9 Reheat the wire loop in the Bunsen flame, as in step 1, and then put it on the heatproof mat to cool.
10 Tape your agar plate with sticky tape like this:
11 Place your agar plate upside down in an incubator at 20-25 °C.
1 Why do you think you held the wire loop in the flame before each time you used it?
2 Why do you think you left your Petri dish upside down? (Hint: Think about condensation.)
3 Look at your Petri dish after a couple of days. Why do you think you streaked the wire loop across the agar so many times? (Hint: See what the first streaks you made look like compared with the last set.)
4 a Do you think that you grew your bacteria well or were there some other things that also grew?
b What could you do to stop anything else growing in your agar?
5 Design a leaflet to explain to someone how to do this experiment safely.
[ observing, considering, evaluating ]
8Cc2 Diseases and their causes
Use some sources of information to complete this table. The bottom row is blank for you to write about another disease. Find out about another disease and fill in the bottom row.
Disease
Symptoms
What it is caused by
How it is spread
chickenpox
Fever. Raised red spots with yellow tops.
virus
cholera
Very bad diarrhoea, dehydration and vomiting.
common cold
diphtheria
Swelling of the throat and difficulty in breathing. May cause some paralysis.
air
mumps
Bad fever. Painful and swollen neck.
polio
Fever. Parts of the body may become paralysed.
air or water
rubella (German measles)
scarlet fever
bacterium
Long period of short, fast coughs ending with a 'whoop' sound.
[ research ]
8Cc3 Diseases
1 The grid below shows the names of some common diseases. Each name has some letters missing. The missing letters are all found in the box. Write in the correct missing letters for each disease.
I
M
G
O
S
Y
C
N
F
D
E
R
U
A
T
H
'S
P
X
Z
Missing letters:
easle flu hick hole let old pet phil pois tub
2 a Which of these diseases is the most common? ________________________________
b How is this disease spread from person to person? ____________________________
_____________________________________________________________________
c Name two other ways that a disease can be spread. ____________________________
3 Look at the letters shaded in grey in question 1. Unmuddle the letters to complete this sentence.
If you catch a disease you are said to be ______________________________ with it.
4 Some diseases are commonly called by shortened names.
a Which disease is commonly called 'flu'? _____________________________________
b Which disease is commonly called 'TB'? _____________________________________
8Cc4 Microbes recap
1 a Name the three main types of microbe.
i ____________________ ii ____________________ iii ___________________
b Which of these is the smallest? ____________________________________________
2 Which type of microbe is used to make:
a bread ________________________ b wine ________________________
c cheese? ________________________
3 a Name one disease caused by a microbe. ______________________________________
b What sort of microbe causes this disease? ___________________________________
c How is this disease spread?_______________________________________________
d Describe one of the symptoms of this disease. ________________________________
______________________________________________________________________
4 a Name a disease caused by microbes that is very common. _______________________
b Name a disease caused by microbes that is uncommon in the UK. ________________
5 Apart from your answer to Question 3c, name two other ways in which microbes can be spread.
i _______________________ ii _______________________
[ knowledge ]
8Cc5 Yellow fever
Yellow fever is a disease found in Central Africa and Central and South America. It causes high temperature, muscle aches, headaches and the gums and intestines start to bleed. Some scientists suggested that it might be spread by coming into direct contact with infected people or their clothes, others thought that it was spread through the air or in the water.
In 1881, Carlos Finlay (1833-1915), a Cuban scientist, suggested that it was carried by mosquitoes, as yellow fever occurred when there were more mosquitoes around. He thought that it was carried in people's blood, since the disease caused bleeding. Mosquitoes have long needle like tubes on their mouths for sucking up blood and so Finlay thought that this could transfer the organism causing the disease. However, he was not able to prove that he was right
In 1900, an American scientist called Walter Reed (1851-1902) went to Cuba.
He took two groups of volunteers. The first group stayed in a dirty hut containing
clothing from yellow fever patients (covered in blood and vomit). They were not bitten by mosquitoes. The second group stayed in a clean hut and were bitten by mosquitoes that had recently fed on people with yellow fever. Only the second group got the disease, and some of them died. This provided the evidence that yellow fever was carried by mosquitoes.
1 Where in the world is yellow fever found?
2 What are the symptoms of yellow fever?
3 a What was Carlos Finlay's theory?
b Why did he think this?
c What is the needle-like tube on a mosquito's mouth called?
4 In Walter Reed's experiment, why did the first group of volunteers stay healthy?
5 In 1901, Reed filtered some blood from a yellow fever patient to remove all the cells and any bacteria. When this filtered blood was injected into another person, the person still got yellow fever. Explain why you think this happened.
6 Mosquitoes breed wherever there is still, calm water. What simple measures do you think the people of Cuba took to stop them getting yellow fever after it was discovered that the disease was carried by mosquitoes?
8Cc6 Ebola disease
Ebola disease is caused by a virus. The first cases of it were discovered in 1976 along the Ebola river, in The Democratic Republic of Congo, Africa. The disease causes a fever, muscle aching, vomiting, very bad diarrhoea, a rash, and eventually bleeding inside and outside the body. Unless treated, it causes death in about 90% of cases, and even if treated one in four people die. There is no cure, but if the people are looked after in hospital their bodies can often fight off the infection.
The disease is spread by touch and it easily spreads from person to person. People can also become infected by touching the dead bodies or by coming into contact with blood, urine, faeces or saliva from an infected person. In one area of Uganda, the virus quickly spread because the people who had died of the disease were given traditional burials. This involved many people washing the dead body and then washing their hands together in a large basin as a sign of unity and togetherness.
When a local doctor first suspects that someone is suffering from Ebola disease, he or she will immediately get in touch with the government health department. In most cases a team of people is then quickly sent from the World Health Organisation. The team consists of doctors, nurses, scientists and teachers. The doctors and
nurses are specially trained to look after the patients without getting infected themselves. The scientists try to work out where the disease originally came from in the area to try to stop it spreading. The teachers tell the local people about the disease and how they can avoid catching it.
1 What sort of microbe causes Ebola disease?
2 How do you think the disease got its name?
3 What are the symptoms of the disease?
4 How is the disease spread?
5 a Which organisation usually sends a team of people to areas where Ebola disease occurs?
b What do you think the doctors and nurses from this team do?
c How do you think the medical team might protect themselves from getting the disease?
d Imagine you were one of the teachers sent to an area like this. What would you advise the people to do to avoid catching the disease?
8Cc7 Malaria
Malaria is a disease that kills about two million people every year. The disease is caused by a protoctist called Plasmodium which is carried by a certain kind of mosquito. An animal that spreads a disease is called a vector.
Plasmodium is a parasite - an organism that lives on and feeds off another living organism. It has quite a complex life cycle:
The life cycle of Plasmodium.
After a person has been infected by Plasmodium, he or she may not feel unwell until the microbes start bursting out of the red blood cells. When this happens, the infected person gets a very high fever, and starts to shiver violently and sweat a great deal.
The mosquitoes that carry malaria are only found in hot countries. They lay their eggs in the still water found in lakes, ponds and swamps. To try to stop people getting malaria, swamps are often drained and insecticides like DDT are sprayed onto the ponds and lakes.
The disease is treated using anti-malarial medicines which kill the Plasmodium if they get into the blood. People travelling to parts of the world where malaria occurs should take these medicines while they are there and continue taking them for two to four weeks afterwards.
1 Define the following terms:
a vector b parasite.
2 Jaundice occurs when people cannot remove a red chemical called bilirubin from their bodies, and their skin and the whites of their eyes go yellow. This chemical is normally removed by the liver. Why do you think people with malaria often have jaundice?
3 a Name one country where you think malaria might occur.
b If a person came back to the UK with malaria, do you think he or she should be kept away from other people? Explain your reasoning.
4 Why do you think that people are told to continue taking anti-malarial medicines for two weeks after they have come back from a country where malaria occurs?
5 What problems might be caused by spraying lakes and ponds with insecticides like DDT?
6 Many scientists are worried about global warming. Name one effect of the UK becoming hotter than it is today. Your answer must contain the word 'malaria'.
8Cd1 Washing with soap
Is washing your hands with soap better than just using plain water? You are going to do an experiment to find out.
1 Write down what you think will happen.
- Petri dish containing agar jelly
- Marker pen - Sticky tape
When clumps of bacteria have grown in your Petri dish, DO NOT open it.
1 Mark lines across the bottom of your Petri dish and label it as shown.
2 Take the lid off your dish and quickly press your right thumb very gently onto the surface of the agar on the section that you marked 'Unwashed'. Put the lid back on quickly.
3 Now wash your hands with water only and shake the drips off. Don't dry them.
4 Repeat step 2 but pressing your right thumb on the section marked 'Washed with water.' Now go to step 5.
5 Wash your hands again with soap and water and shake the drips off. Don't bother drying them.
6 Repeat step 2 but press your right thumb on the section marked 'Washed with soap and water.' Now go to step 7.
7 Tape the lid onto your Petri dish using sticky tape, like this:
8 Place your dish upside down in a warm place for 48 hours.
9 Wash your hands again - with soap!
2 Draw a circle and divide it into sections, as your dish was. Now draw where you can see clumps (colonies) of bacteria inside your Petri dish.
3 In which section of the dish did most bacteria grow?
4 Why do you think this happened?
5 Which is better - washing with just water or with soap and water, or doesn't it make any difference?
6 What other experiment could you do to find out if washing your hands for longer makes a difference?
8Cd2 Natural defences 1
Cut out the outline of the human and the information boxes.
1 Stick the boxes around the human and draw labelling lines to the parts of the body that match the information.
2 Fill in the missing words in the information boxes. The words to use are in the word box.
ciliated gullet microbes mucus scab skin stomach white windpipe
A chemical in your tears kills_____________.
Your nose produces _____________which
traps microbes.
Cells in your _____________ also produce
mucus. ____________ epithelial cells sweep
the mucus to the top of your _____________
to be swallowed.
_____________ covers your whole body. It
stop microbes getting in.
If you get a cut a _____________ forms.
_____________ blood cells destroy microbes.
Your _____________ contains acid which
kills microbes.
8Cd3 Microbes and food
We can stop some microbes making food go off in a variety of ways. Some are
shown here.
Freezing food stops microbes growing but it does not kill them.
Before being put into cans, the food is heated to 120 °C. This kills the microbes. The cans are sealed so that no more microbes can get in.
Vinegar is used to pickle some foods. The vinegar makes the pH too low (too acid) for the microbes to survive.
Some foods are dried. This stops microbes getting the moisture they need to grow but it does not kill them.
Milk is heated to 70 °C for 15 seconds which kills most of the bacteria. This is called pasteurisation.
Some foods have lots of salt added to them. This kills the microbes. In the past, salt was so important for this that Roman soldiers were given some of their wages in salt! The word 'salary' comes from the Latin word for salt - 'sal'.
1 a Which ways of stopping food going off involve killing bacteria?
b For each of these ways, name one food that is treated in this way.
2 Peas can be canned or frozen. Which of these will contain living bacteria?
3 a What is pasteurisation?
b Pasteurised milk still goes off after a while. Why do you think this is?
4 Why do you think salt was so important for Roman soldiers?
5 Why are the bacteria killed off in a jar of pickled onions?
6 What conditions (e.g. temperature) do microbes like?
8Cd4 Diseases concept map
1 People do not get diseases caused by microbes very often, although we are surrounded by many harmful microbes. Write down two short sentences to try to explain why not. There is no right or wrong answer to this question.
__________________________________________________________________________
2 Using the words in the box, complete the concept map on the second page of this sheet.
3 Add one more link to the concept map.
4 Make sure you complete the concept map before answering this question.
If you don't think you answered Question 1 very well, re-write your sentences here. If you think that your answer to Question 1 was OK then write down two further ideas about why people do not get diseases very often.
canning cooking disinfectant hygiene immunity
skin soap vaccinations viruses white blood cells
8Cd5 Natural defences 2
In the diagram below, each of the labelled parts shows one of the body's ways of stopping getting infected by a disease.
1 What are the names of the parts labelled A-D?
2 Which of the parts A-G try to stop microbes entering the body?
3 Which of the parts A-G try to kill microbes?
4 Explain how these body parts help to stop the body becoming infected by microbes.
a Part B b Part D
5 Why do you think that it is important for clots (scabs) to form over cuts quickly?
6 Name one part of the blood needed for this process of clotting to occur.
7 Some white blood cells surround (engulf) microbes and kill them. Others produce antibodies. For each drawing explain what is happening.
b
c
8 Look at this drawing.
a Where would you expect to find this group of cells?
b Write down what the cells labelled 'X' and 'Y' do.
c What is the cell labelled 'Y' called?
8Cd6 Louis Pasteur
Louis Pasteur (1822-1895) founded the study of microbes (called 'microbiology'). Microbes were first seen by a Dutch scientist called Antoni van Leeuwenhoek in 1674, but nobody realised their importance and people thought they were produced by spontaneous generation. This theory said that the food or drink that they were found in had created them.
A brewer called Bigo asked Pasteur to help him work out why wine sometimes went off when it was fermenting. Pasteur discovered that fermentation was caused by a microbe and that the wine went off if other sorts of microbes got into it at the same time.
He also discovered that the microbes that made the wine go off came from the air. He demonstrated this by taking flasks of a clear soup called broth. Some flasks had large curled tubes, and others did not. He boiled the broth in the flasks and then left them to sit around his laboratory. The broth in the flasks with the long tubes did not go off, because the microbes got stuck in the tubes and could not reach the broth. This disproved the theory of spontaneous generation.
Emperor Napoleon III then asked Pasteur to find a way of stopping his wine going off after it had been bottled. Pasteur invented pasteurisation to stop this happening.
Pasteur later showed that some diseases were caused by microbes from the air. He came up with what is called the germ theory of disease which we now know is correct.
1 a Who was the first person to see microbes?
b What is the study of microbes called?
2 a Before Pasteur, how did people think that microbes came to be in food and drink?
b What was this theory called?
c What would have happened in Pasteur's flasks if this theory had been correct?
3 Some people thought that microbes were caused by the air itself, rather than microbes in the air. How does Pasteur's experiment also disprove this theory?
4 a Pasteur discovered that a microbe caused fermentation. Which microbe?
b Suggest what other sort of microbe might have made the wine go bad.
5 a Why do you think wine that tasted all right before it was bottled might go off in the bottles?
b Name the process Pasteur invented to stop this happening.
c What common drink is this process also used for today?
8Cd7 Joseph Lister
In the early 19th century, hospitals were dirty places and many people died after having operations. Their wounds often started to rot, a condition known as sepsis. The German chemist Justus von Liebig (who invented the Liebig condenser) thought that sepsis was a kind of slow combustion caused by exposing flesh to oxygen. He said that to prevent it, wounds should be covered in plaster to stop air getting to them. This did not work!
In 1861, Joseph Lister became a surgeon at the Glasgow Royal Infirmary. During his first four years he amputated many septic limbs and nearly half of these patients died because the cut ends also went septic. Then he read about Louis Pasteur's theory that diseases were caused by microbes in
the air. Pasteur had shown that fermentation was caused by microbes and Lister thought that a similar process caused parts of the body to rot.
Lister knew that carbolic acid was being sprayed onto sewage in Carlisle. Cattle in the area used to get a disease when sewage was spread on their fields but they did not get the disease when sewage treated with carbolic acid was used. Lister thought that carbolic acid might kill microbes and so he put his surgical equipment in carbolic acid before operations. He also soaked wounds with the acid and bandaged them up
Joseph Lister (1827-1912).
with dressings soaked in it. In 1867 he reported to the British Medical Association that no sepsis had occurred in his operations for nine months.
1 a What is 'sepsis'?
b What did von Liebig think sepsis was caused by?
c What did Pasteur think sepsis was caused by?
2 a What is an amputation?
b Why do you think so many limbs needed amputation in Lister's time?
c Why do you think many fewer amputations are needed today?
3 a Why did Lister choose to use carbolic acid?
b Why do we now refer to carbolic acid as an 'antiseptic'?
4 Lister once wrote 'You must be able to see, with your mental eye, the septic ferments.'
a What do you think he meant by 'septic ferments'?
b Why did he have to imagine them with his 'mental eye' rather than just look at them?
5 A mighty creature is the germ, though smaller than a pachyderm.
His customary dwelling place is deep within the human race.
His childish pride he often pleases by giving people strange diseases.
a What does the poet mean by a 'germ'?
b Find out what a pachyderm is.
c Find out who this poem was by.
d How does the poem continue?
[ literacy, knowledge, research ]
8Ce1 Antibiotics
Antibiotics are medicines that kill bacteria. There are many different types of antibiotics and different types kill different sorts of bacteria. You are going to find out which of two antibiotics is better at killing some bacteria. The antibiotics are called streptomycin and penicillin.
- Petri dish containing agar and covered with bacteria
- 1 small disc of filter paper
- 1 disc containing streptomycin
- 1 disc containing penicillin
- Beaker of distilled water - Sticky tape
- Marker pen - Forceps
- Beaker of ethano- - Paper towel
When the bacteria have grown in your Petri dish, DO NOT open it.
1 Take the plain filter paper disc and place it in distilled water. Place it on a paper towel to dry.
2 Mark lines across the bottom of your Petri dish. Label one section 'penicillin', one section 'streptomycin' and the other section 'water'.
3 Take the forceps out of the ethanol and dry them using a paper towel.
Do not touch the tips of the forceps. Using the dry forceps, take one of the antibiotic discs and place it onto the correct section of your Petri dish.
Put the forceps back into the ethanol to clean them. Repeat this step with each disc.
4 Tape the lid onto your Petri dish with sticky tape, like this:
5 Place your dish upside down in a warm place for 48 hours.
1 The Petri dish is covered with bacteria which will grow in the warm place. They will not grow where there is a chemical that kills them. Which discs do you think will have the areas without bacteria around them? Why do you think this?
2 Without opening your Petri dish, use a ruler to measure the diameter of each circle that has no bacteria growing in it.
3 Write down your measurements. Which circle was bigger?
4 Which antibiotic was better at killing these bacteria?
5 How do you know this?
[ observing, considering ]
8Ce2 Microbes crossword
7
8
9
12
13
14
15
17
18
19
20
ACROSS
3 A type of medicine that will kill bacteria but not viruses.
8 Some microbes pass from person to person through this (e.g. flu viruses).
10 A substance added to drinking water to kill the bacteria in it.
11 This microbe is used in brewing and baking.
13 This sort of respiration needs oxygen from the air.
15 See 2 down.
16 Colds and flu are caused by these.
19 A way of treating milk to stop it causing diseases.
20 A disease which babies are often immunised against.
DOWN
1 See 5 down.
2 and 15 across. This disease is caused by a fungus that grows in the damp and warm areas between toes.
4 When you get a disease you are said to be _____________ by it.
5 and 1 down. A gas produced by respiration.
6 A food made using a microbe.
7 Tiny organisms that you need a microscope to see.
9 and 12 down. A disease caused by bacteria found in food.
12 See 9 down.
14 These microbes cause diseases like tuberculosis and syphilis.
17 The outer covering of your body that stops microbes getting inside.
18 Microbes like bacteria need _____________ and damp places in which to grow.
8Ce3 Immunisation
1 White blood cells in your body make antibodies. These attach to microbes and help to destroy them. Each different microbe has different shapes on its outside and the white blood cells need to make different antibodies to fit the different shapes. On the diagrams below, draw lines to show which antibodies will fit which microbes.
2 Use the words from the box to complete the sentences about immunisation.
antibodies blood disease injection microbes vaccine white
In an immunisation you are given an ________________ containing a ________________ .
This is some of the _________________ that normally cause a _________________ but
which have been treated so that they do not. It makes _________________
_________________ cells produce _________________ . These attack the vaccine and some
of them stay in the blood.
3 If a microbe cannot cause a disease in you, you are said to be immune. Explain how a vaccine makes you immune.
_________________________________________________________________________
8Ce4 Microbes concept map
1 Make a list of all the key points covered in this Unit. You should have key points on microbes, diseases and defences against diseases.
2 Design a concept map to cover these points. Do not add in any linking phrases, just write in the key points and link them together with lines. You might start like this.
3 Using your concept map, make a list of ten questions to ask other pupils in your class about this Unit.
Optional extra
4 Pick out six key points from the list that you made in Question 1.
5 Combine your list with two or three other people's lists.
6 In your group agree a final list of ten key points.
7 One member of your group should present your key points to the class. Decide how your key points are going to be presented.
8 After each group has presented their key points, you will need to put all the key points into groups to make a class summary for the Unit. Think about what will be the best way of doing this.
8Ce5 Disease and immunisation
1 What is a vaccination?
2 The table shows the number of deaths caused by a disease called diphtheria.
a Plot the information on a graph.
b In which decade do you think the vaccine for diphtheria was introduced in England and Wales?
c Explain how you worked out your answer to part b.
Year
Number of deaths from diphtheria
1910
4920
1920
4875
1930
2706
1940
2721
1950
35
1960
3 Antibodies are produced by some types of white blood cell. Each sort of antibody needs to be specially made to help kill a different sort of microbe. Each microbe has different shapes on its outside covering. The antibodies attach themselves to these shapes.
a Why do you think it takes time for antibodies to be made once you have been infected by a microbe?
b Antibodies for the measles virus will not work against the chickenpox virus. Why not?
c If you get chickenpox, you will not get it again. Explain why not.
d Draw a diagram to show what shape of antibody is needed to attach to this microbe.
e Babies get antibodies from their mothers through the placenta and through breast milk. These antibodies last for only about 2-3 months in the baby. What benefit do you think they have for the baby?
[ numeracy, knowledge ]
8Ce6 Disease and death
1 The graph shows the number of deaths from infectious diseases in the UK for most of the 20th century.
a If there were 56 million people living in the UK in 1981, work out roughly how many people died of an infectious disease.
b Describe the trend that the graph shows.
c Write down as many ways you can think of why this trend has occurred. There are at least four reasons.
d In which period of 10 years does the death rate decline the most rapidly?
e Give one reason why the death rate drops most dramatically during this time.
f There were two periods when the death rates went up again. Suggest one reason why theses increases happened.
g In fact for the first of these increases there was another reason. Find out what this was.
2 Sometimes people get worried about having a certain immunisation because they do not think that the vaccine is safe.
a Look at the graph and explain why you think it is the shape that it is.
b Do some research to find out whether your explanation is correct.
Whooping cough in England and Wales, 1972-1997.
3 Syphilis is a disease that is spread through sexual intercourse. It used to be a major killer but can now be treated with antibiotics. There is no vaccine for it.
a Do you think that the number of deaths from syphilis increased, decreased or stayed about the same during the 20th century? Explain your answer.
b Do you think that the number of cases of syphilis increased, decreased or stayed about the same during the 20th century? Explain your answer.
[ knowledge, considering, research ]
8Ce7 Edward Jenner
Smallpox was a very serious disease which caused huge spots filled with pus to appear all over the body. In the 18th century nearly everyone caught the disease and 25% of victims died. Those who lived had terrible scars left by the spots, especially on their faces.
As a young man, Edward Jenner (1749-1823) was given smallpox on purpose. The idea was that by giving it to people when they were young, fit and healthy they would survive better than if they caught it when they were older. This was a very dangerous thing to do and many people died. Jenner survived but later in his life, he set about trying to stop this practice.
Jenner noticed that girls who looked after cows rarely caught smallpox. He came up with a theory that if you gave people a disease caught from cows, called cowpox, they would be protected from smallpox. Many people thought he was mad and some even thought that anyone who was given cowpox would turn into a cow!
He tested his theory in 1796, when a milk maid called Sarah Nelmes caught cowpox. He asked an eight-year-old boy, called James Phipps, to come to his house, where he squeezed pus from a cowpox spot on Sarah's hand into a cut on James' arm. The boy caught cowpox. Eight weeks after this, he squeezed pus from a smallpox spot into another cut on James' arm. The boy did not get smallpox. This was the first vaccine (although Jenner knew nothing of microbes). The word 'vaccine' comes from the Latin for cow - vacca. Thanks to immunisation, smallpox no longer exists in the world (although some of the viruses are kept in laboratories for research).
Cowpox spots on the hand of Sarah Nelmes.
1 a Why was Jenner given smallpox as a young man?
b Describe the symptoms that Jenner might have suffered.
2 a What was Jenner's theory?
b What observations did he make to come up with this theory?
3 Why did James Phipps not catch smallpox?
4 a What is a vaccine?
b Why do you think it got this name?
5 These are the first two lines of a poem by William Allingham (1824-1889), called 'The Milk Maid':
O where are you going so early? he said;
Good luck go with you, my pretty maid;
Why do you think milk maids were renowned for being pretty in the 18th and early 19th centuries?
8Ce8 Immunisation - it's logical!
This is a logic problem. You need to work out when a vaccine for a certain disease was developed and the full name of the person who developed it. Read the information below and put ticks in the squares on the grid for facts that are definitely true. You can mark other boxes with a cross for things that are definitely false. You should then be able to work out the rest of the information and fill in the details in the table at the bottom.
Pittman, who developed a vaccine in 1995, was not called Max, who was actually the man who developed a vaccine for yellow fever. Pasteur, the famous Frenchman, developed a vaccine for rabies. Albert Calmette was a pupil of Pasteur and developed his vaccine before 1950, but after Pasteur developed his vaccine. Salk was not called Margaret and nor was Margaret the person who developed a vaccine for tuberculosis. A polio vaccine was developed by a man after 1923 but his name was not Louis. 1937 saw the development of a yellow fever vaccine. Theiler was an American man who was not called Louis or Jonas.
First name
Last name
Vaccine
Date
[ literacy ]
8C Summary Sheets
Microbes
Microbes (short for micro-organisms) can only be seen using a microscope. There are three main types: viruses, bacteria and fungi. The most common fungus microbes are yeasts.
Viruses are smaller than bacteria which are smaller than yeasts.
Viruses are often not considered to be living because they do not carry out any of the seven life processes for themselves.
Bacteria and yeast are important in making foods and drinks. Yeast is used to make bread dough rise. It uses oxygen, from the air found in pockets in the dough, for aerobic respiration. This process produces carbon dioxide which makes the bread rise.
glucose + oxygen ¾→ carbon dioxide + water (+ energy)
(a sugar)
Yeast are also used to make beer and wine. In this case there is no air and so they use anaerobic respiration. When yeast use anaerobic respiration it is called fermentation. The ethanol is a waste product of this reaction.
glucose ¾→ carbon dioxide + ethanol (+ energy)
The numbers of an organism in an area are called a population. In good conditions (warm, moist, plenty of sugar) a population of yeast will grow rapidly. The population stops growing if something runs out (eg sugar). The thing that stops the population growing is called a limiting factor.
Diseases
Some microbes cause infectious diseases (diseases that can be spread from person to person). The microbes are said to infect you. The effects the microbes have on your body are known as symptoms. Microbes can be spread by the air, water, touch, food, animals and sex.
Microbe that causes it
Colds and flu
Virus
Sore throat, running nose, fever
Air
Food poisoning
Bacteria
Vomiting, diarrhoea
Food
Cholera
Water
Athlete's foot
Fungus
Sore cracked skin between the toes
Touch
Some ways that diseases can be stopped from spreading are:
- making sure sewage is treated and disposed of properly
- adding chlorine to water to kill bacteria
- pasteurising milk
- using disinfectants, antiseptics and soaps
- immunising people with vaccines.
Your body has natural defences to stop microbes getting in (eg skin, mucus in the windpipe and nose, ciliated epithelial cells to sweep mucus along). Your body also has ways of destroying microbes. These include:
- a chemical in tears that kills some bacteria
- acid in the stomach that kills some bacteria
- white blood cells that engulf microbes
- other white blood cells that make antibodies to help destroy microbes.
Babies do not have fully developed immune systems. Antibodies can pass through the placenta and are found in breast milk. These help the baby to fight infections.
For many diseases, once you have had the disease (or been immunised) you will not get it again (e.g. chickenpox). This is because the antibodies against these microbes stay in the blood.
Some diseases can be cured using antibiotics which are medicines which kill off bacteria. Some bacteria, however, are unaffected by antibiotics - they are resistant to them.
8C Target Sheet
Topic
Targets
Before the unit
I have learned this
I have revised this
8Ca
Know the names of the different sorts of microbes.
Know the sizes of the different sorts of microbes.
Know how viruses live.
Know what microbes look like.
8Cb
Know how some microbes are useful.
Know what aerobic respiration is.
Know what fermentation is.
Know how the sizes of populations are controlled.
8Cc
Know that some microbes cause diseases.
Know the names of some common diseases caused by microbes.
Know how these diseases are spread.
Know what a theory is.
8Cd
Know how people stop diseases spreading.
Know how our bodies try to stop microbes getting into our bodies.
Know how our bodies try to kill microbes if they do get into our bodies.
Know what antibodies are and what they do.
8Ce
Know what an antibiotic is.
Know what a vaccine is and how it works.
Know what immunity is.
Know that some microbes are not affected by antibiotics.
8C Word Sheets
Word sheets that include new words from the 'Focus on:' pages are available on the Exploring Science website.
8Ca - A hidden world
Word
Pronunciation
Meaning
A type of microbe bigger than viruses. (plural = bacteria)
fungus
Organisms which are different from animals, plants and bacteria. Examples include mushrooms and yeasts. (plural = fungi)
microbe
Short for micro-organism.
micro-organism
A very small living thing.
organism
A living thing.
The smallest type of microbe. Many people think that they are not living because they do not carry out the seven life processes for themselves.
yeast
A type of fungus with only one cell and therefore a microbe. They are bigger than bacteria.
8Cb - Microbes in action
aerobic respiration
air-rO-bick
A type of respiration that needs oxygen. Releases energy from a sugar (glucose) and produces carbon dioxide as a waste gas.
anaerobic respiration
an-air-rO-bick
A type of respiration that does not need oxygen.
budding
The way yeast cells divide. A new small cell (a bud) starts to grow out from another cell.
ethanol
Often just called 'alcohol'. Produced by yeast when they ferment sugar.
fermentation
The type of anaerobic respiration carried out by yeast. It produces carbon dioxide and ethanol.
limiting factor
Something that stops a population growing.
population
The numbers of a certain organism found in a certain area.
8Cc - Under attack/Cholera: The evidence
disease
When some processes that happen in the body do not work in the way they should.
evidence
Information that helps to prove that an idea is correct.
fever
A high body temperature.
infect
When a microbe gets into your body you are 'infected' by it.
infectious
in-feck-shus
A disease that can be spread from person to person or from animal to person is infectious.
observation
Looking carefully at things and recording what you see or measure.
prediction
pred-ick-shun
An idea about what will happen when you change something.
symptoms
The effects that a disease has on your body.
theory
theer-ree
A scientific idea that can be tested.
8Cd - Self defence
antibody
Small chemicals made by some white blood cells. They attach to microbes and help to destroy them.
antiseptic
Weak disinfectant safe to use on human skin.
ciliated epithelial
sil-lee-ay-ted
Cells in the trachea which have microscopic hairs (cilia) growing from them which
cell
eppy-theel-ee-al
wave to move mucus up to the gullet to be swallowed.
clot
When blood becomes solid. Makes a 'scab' when it is on the surface of the skin.
disinfectant
Strong chemical used to kill microbes.
engulf
When a white blood cell completely surrounds a microbe and destroys it, it is said to engulf the microbe.
mucus
mew-cus
Sticky substance used to trap microbes and dust. Found in nose and trachea.
natural defences
Your body's way of trying to keep microbes out (e.g. skin) or killing them if they get inside you (eg stomach acid).
pasteurisation
pas-ter-eyes-ay-shun
Milk is heated up to 70°C for about 15 seconds which is enough to kill the most harmful bacteria in it.
scab
A dry blood clot on the surface of the skin.
trachea
Another name for the windpipe.
white blood cell
A type of blood cell which helps to destroy microbes. They either engulf microbes or make antibodies.
8Ce - Beating infections/Medicine men
antibiotic
ant-ee-by-ot-tick
Medicine that can kill bacteria but not viruses.
immune
imm-you'n
If you cannot get a disease you are said to be 'immune' to it.
immunisation
imm-you'n-eyes-ay-shun
Making people immune to diseases.
medicine
A drug that helps the body to ease the symptoms of a disease or cure the disease.
resistant
Bacteria that are not affected by an antibiotic are said to be resistant to it.
vaccine
vack-seen
A mixture containing microbes which normally cause disease, which have been treated so that they don't. Injected into people to make them immune.