BIODIVERSITY AND CLASSIFICATION OF MICRO-ORGANISMS
30 JANUARY 2013
Lesson Description
In this lesson we will:
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Look at the basic structures and general characteristics of
o Viruses
o Bacteria
o Protists
o Fungi
Discuss the role of micro-organisms in maintaining balance in the environment.
Investigate the symbiotic relationships related to micro-organisms.
Discuss a disease of each of the four groups of micro-organisms.
Look at the use of micro-organisms in the production of medicines and the traditional uses of
micro-organisms.
Key Concepts
General characteristics of micro-organisms
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A virus is acellular, parasitic, extremely small and has many different shapes.
It uses the host to replicate itself so it multiplies inside a host’s cell.
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Bacteria have a cellular structure are prokaryotes and unicellular with three distinctive
shapes – coccus (spherical), bacillus (rod shaped) and spirillus (spiral shaped).
Bacteria have three ways of obtaining energy; photosynthesis, chemosynthesis or
Heterotropism.
Bacteria reproduce through binary fission.
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Protista is a kingdom with three main groups that are classified according to how they obtain
their nutrition and how they move
Protozoa are animal-like protists that are heterotrophic or parasitic and move using
pseudopodia, cilia or flagella. Plant-like protists are autotrophic and can be unicellular or
multicellular. Fungus-like protists are heterotrophic and are decomposers.
Fungi can be unicellular or multicellular, are all eukaryotic and have cell walls made of chitin.
Multicellular fungi are inter-twined together by threads called hyphae.
Fungi are heterotrophic saprophytes and get their food from whatever substrate they grow
on. They replicate both sexually and asexually.
Role of micro-organisms
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Micro-organisms maintain the balance in the environment because they are found
everywhere and continually recycle nutrients and energy
Viruses control ecological processes such as nutrient cycling, bacterial and algal
biodiversity. They are also pathogens and cause disease
Bacteria are producers, are decomposers or recyclers of nutrients, in particular nitrogen
Protists produce food, are parasites, pathogens or decomposers
Fungi convert organic matter by decomposing it and making nutrients available but can be
pathogenic too
Symbiotic relationships
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Viruses are parasitic
Bacteria can have parasitic or mutualistic relationships with other organisms
Fungi have symbiotic relationships with some organisms
Diseases
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Viruses can cause rabies, HIV/AIDS, distemper, foot-and-mouth, influenza, chickenpox, and
measles. Illnesses caused by viruses are often difficult to cure but vaccines work to protect
an organism against the virus
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Bacteria cause diseases in plants, animals and humans. Examples of diseases are
Tuberculosis, cholera, dysentery, syphilis and food poisoning. Bacterial infections can be
treated with anti-biotics
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Protozoa can cause sleeping sickness, amoebic dysentery, and malaria. Treatment involves
drugs that interrupt the life cycle of the protozoa
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Fungi can cause diseases in plants, animals and humans. Common fungal diseases in
humans are ringworm, thrush and athlete’s foot. In plants they cause rust.
Treatment of rusts is by fungicides but prevention is better than cure. Treatments of
ringworm, thrush or athlete’s foot are usually topical creams or oral medication
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Uses of micro-organisms in tradition and technology
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Bacteria produce insulin through genetic engineering
Fungi produce penicillin which is a form of antibiotic
Traditionally yeasts are used to make beer, wine, cheese and yoghurt
Demonstration
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Bread mould
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Brewers yeast
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Cheese
Questions
Question 1
(Adapted from Life Sciences/P1 DoE/Exemplar 2007 NSC.)
A sample was taken from a patient suffering from a throat infection. The bacteria on the swab were
cultured on a nutrient agar in a petri-dish. A multidisc with a different type of antibiotic at the end of
each of its six arms was then placed on top of the bacteria. The two halves of the petri-dish were then
sealed together and placed in an incubator at 30 ºC. The following diagram shows the result of the
investigation after 48 hours:
a.)
State ONE difference in activity between antibiotics B and F.
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The patient was known to be allergic to antibiotic B.
b.)
c.)
Which antibiotic should the patient be given?
Explain your answer to QUESTION 1.b
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The organism causing this infection seems to be resistant to two of these antibiotics.
d.)
e.)
Which TWO antibiotics are referred to in the statement above?
Explain your answer to QUESTION 1 (d).
The patient was given a 5-day course of the appropriate antibiotic. Explain why it is
important to finish the course of antibiotics, even if you feel better.
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Question 2
In the early part of the twentieth century, spiders' webs (in which many fungal spores were trapped)
were placed on small cuts and wounds. Suggest ONE reason for the following:
a)
b.)
Why this might have been a useful procedure.
Why it could have been dangerous?
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Question 3
Antibiotics are ineffective against viral diseases. Why then, are antibiotics sometimes given to people
suffering from viral infections, such as influenza (flu)?
(2)
Question 4
State TWO ways in which an antiseptic is different from an antibiotic.
Links
Learn Xtra Grade 11
Viruses and Bacteria
http://www.mindset.co.za/learn/node/54985/22/63512/17298/63521
Science presentation: Viruses, Bacteria, Fungi, and Protists
http://www.youtube.com/watch?v=H15pcSBshWY
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