Download 7.3 Search for microbes – Questions and answers Q1. Bk Ch7 S7.3

7.3 Search for microbes – Questions and answers
Q1.
Bk Ch7 S7.3 Q1
What is a microbe?
A1.
Bk Ch7 S7.3 A1
A microbe is a microscopic organism. Many microbes can cause disease in plants or animals.
Q2.
Bk Ch7 S7.3 Q2
Draw a timeline to identify and summarise developments in our understanding and management of
disease-causing microbes. Include the work of Louis Pasteur and Robert Koch.
A2.
Bk Ch7 S7.3 A2
Before mid-1600s: People believed that living things including the agents of disease were produced by
‘spontaneous generation’.
1800s: Louis Pasteur:
•
demonstrated that fermenting wine contains micro-organisms
•
conducted an experiment to show that micro-organisms exist in the air and these can be
responsible for food spoilage
•
developed the technique of killing micro-organisms in foods by raising the temperature of the
food to 55°C for several minutes
•
showed that anthrax is caused by a bacterium and developed the first inoculation technique by
injecting a weakened strain of the disease into sheep who subsequently developed a resistance to
anthrax
•
developed vaccines against anthrax, chicken cholera, swine erysipelas
•
saved the life of a child bitten by a rabid dog by using a rabies vaccine.
1800s–1900s: Robert Koch:
•
isolated anthrax bacteria from the blood of infected animals
•
established that the blood of animals with an infectious disease contained the micro-organisms
that cause the disease while the blood of healthy animals did not show the presence of such
micro-organisms
•
showed that when blood from an infected animal was injected into a healthy animal the animal
contracted the disease
•
demonstrated that micro-organisms were the cause of disease and not some other factor in blood.
He did this by isolating micro-organisms from the blood of infected animals and then injecting
only the micro-organisms into healthy animals—the healthy animals then contracted the disease.
Q3.
Bk Ch7 S7.3 Q3
Consider each of the following different kinds of organisms:
a
prions
b
viruses
c
bacteria
d
protozoans
e
fungi.
For each, answer the questions that follow:
i Describe the organism.
ii List some diseases caused by the organism.
A3.
Bk Ch7 S7.3 A3
a
i
ii
Prions are proteins that have been altered from their normal shape and are the cause of brain
diseases in mammals.
Bovine spongiform encephalopathy (mad cow disease), Creutzfeldt–Jakob disease.
7.3 Search for microbes QA
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b
c
i
ii
i
ii
d
i
e
ii
i
ii
Viruses are not cellular but rather a piece of DNA or RNA enclosed in a protein coat.
Smallpox, measles, influenza, AIDS.
Bacteria are procaryotic cells. Some bacteria are the cause of disease in plants and animals
but most are not.
Tetanus, tuberculosis, pneumonia and foot rot in animals; crown gall, some leaf spot
diseases in plants.
Protozoans are single-celled eucaryotic organisms with animal-like characteristics. Many
kinds of protozoans are free-living but some are the cause of parasitic disease in animals.
Giardia infection, amoebic dysentery.
Fungi are eucaryotic organisms, some of which are unicellular such as yeasts, but most are
composed of a mycelium and fruiting body; a mushroom is an example.
Ringworm in animals; mildew and rusts in plants.
Q4.
Bk Ch7 S7.3 Q4
a
b
What is a macroparasite?
Make a list of macroparasites that infect
i animals
ii plants.
In each case indicate whether the organism is an external or an internal parasite.
A4.
Bk Ch7 S7.3 A3
a
b
A macroparasite is a parasite that is large enough to be seen with the naked eye.
Examples:
i Lice, mites, ticks and fleas are external macroparasites that infest animals. Tapeworms,
roundworms and flukes are examples of internal animal macroparasites.
ii Macroparasites that affect plants include mites, aphids, borers and scale insects.
Q5.
Bk Ch7 S7.4 Q5
a
b
What is an antibiotic?
Briefly outline the role of antibiotics in the management of infectious diseases.
A5.
Bk Ch7 S7.4 A5
a
b
An antibiotic is a substance that inhibits the growth of disease-causing bacteria.
Antibiotics combat bacterial infections. For example penicillin damages or destroys the cell walls
of bacterial cells. Streptomycin interferes with the process of protein synthesis in bacteria.
7.3 Search for microbes QA
Copyright
© Pearson Australia (a division of Pearson Australia Group Pty Ltd)
page 2 of 2