Worksheet B2f 3
MRSA ‘superbugs’
Read the information in the box and then answer the questions below.
MRSA
What is MRSA?
MRSA comes from a common family of bacteria called Staphylococcus. A lot of people carry the
bacteria in their throats without becoming ill. MRSA is any strain of the bacteria that is resistant to
antibiotics. The number of deaths from MRSA doubled between 1999 and 2003.
Where did MRSA come from?
MRSA evolved because of natural selection. There are lots of different strains of the bacteria. Each
strain has slightly different DNA. The DNA is constantly mutating as the bacteria reproduce. Some
of these mutations are more resistant to antibiotics than others. When people take antibiotics, the
less resistant strains die first and the more resistant strains are harder to destroy. If people do not
finish their courses of antibiotics the more resistant strains survive to reproduce and pass on their
DNA. In this way more and more strains evolve to be resistant to antibiotics – even new antibiotics.
Why is MRSA a problem in hospitals?
The risk of people dying from MRSA in hospitals is higher than for people outside hospital
because:

patients are already weak, making them more likely to become infected

MRSA is easily passed on when doctors and nurses touch different patients.
Can MRSA be stopped?
MRSA infections are difficult but possible to treat. Patients need very high doses of antibiotics to
make sure all the bacteria are destroyed. New antibiotics can also be used until the bacteria
develop resistance.
QUESTIONS
1
Name the family of bacteria MRSA belongs to.
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2
What is MRSA?
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3
How did the number of deaths from MRSA change between 1999 and 2003?
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Worksheet B2f 3 Continued
4
Which part of MRSA mutates?
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5
Describe how MRSA has evolved.
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6
Why is it important to complete a course of antibiotics?
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7
Why is MRSA a problem in hospitals?
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8
How can MRSA be treated?
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9
Suggest two ways hospitals can prevent the spread of MRSA among their patients.
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Worksheet B2f 4
Theories of evolution
The theory of evolution that Jean Baptiste de Lamarck (1744–1829) developed was simple. He
believed that the characteristics gained by an individual during its lifetime would be passed on to the
next generation. He called this the theory of ‘acquired characteristics’. These characteristics would
include use and misuse of the body, as well as accidents.
This is how Lamarck’s theory would explain how giraffes developed long necks:

giraffes stretch their necks to get leaves from tall trees

their offspring would then have slightly longer necks

each generation would have longer and longer necks.
Charles Darwin worked as a scientist on board the ship HMS Beagle and sailed around the world from
1831 to 1836. He recognised four important facts.

Organisms produce far more offspring than survive.

Population numbers tend to remain fairly constant.

Offspring are slightly different from their parents; this he called variation.

Characteristics inherited from parents are passed on to the next generation.
Darwin then produced a theory to explain these facts. It is called the theory of ‘natural selection’.
1
Darwin’s explanation for why cacti have deep roots is explained in the diagram below.
Worksheet B2f 4 Continued
QUESTIONS
1
Use Darwin’s theory to explain why giraffes have long necks.
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2
Use Lamarck’s theory to explain why cacti have long roots.
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3
a
Suggest which scientist, Lamarck or Darwin, had the correct idea about natural selection.
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b
Explain your answer.
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Worksheet B2f 5
Survival of the fittest word search
There are nine words connected with the lesson on survival of the fittest hidden in the word grid below.
The words may be horizontal, vertical, forwards or backwards. See if you can find all of the words.
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B2f 2
Technician’s notes
Starter activity
Prepare large pictures of:

Sumo wrestler

professional footballer
Class activity – Animal pictures
Prepare pictures of animals from different habitats. (Could use those prepared for lesson B2b Part 1.)
B2f 2
Answers
Worksheet B2f 3 – MRSA ‘superbugs’
1
Staphylococcus
2
Any strain of the Staphylococcus bacteria that is resistant to antibiotics
3
Doubled
4
DNA
5
Check description for accuracy
6
To ensure the more resistant strains are destroyed and cannot reproduce and pass on their
DNA
7
Patients are already weak, is easily passed from patient to patient by doctors and nurses
8
Very high doses of antibiotics; new antibiotics
9
Any two sensible suggestions
Worksheet B2f 5 – Survival of the fittest word search
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