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Summary microorganisms Life sciences.Grade 11 IEB, 3 In 1, ISBN: 9781920686543 Life Sciences (Biology)
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Grade 11 Life sciences - Life Sciences (Biology)
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Grade 11 Life sciences - Life Sciences (Biology)
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Grade 11 Life Sciences - Life Sciences (Biology)
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1Microorganisms
Introduction To Microorganisms
Grade 10 Recap
Living
Organisms
Monera Protista Fungi Plantae Animalia
Living organisms may be classified into 2 groups according to their cell structure:
o Prokaryotes
o Eucaryotes
Living
Organisms
Prokaryotes Eukaryotes
Monera
Protista Fungi Plantae Animalia
(Bacteria)
Prokaryotes Eukaryotes
Organisms without a true nucleus Organisms with a true nucleus
DNA isn’t enclosed by a nuclear membrane Their DNA is enclosed by a nuclear
and occurs freely in the cytoplasm membrane inside the nucleus
Membrane-bound organelles are absent Membrane-bound organelles occur in the
cytoplasm
Microorganisms
Some living organisms are so small they cannot be seen with the naked eye these =
microorganisms
Micro – Small
Macro – Big
There are several groups of microorganisms, which incl:
Viruses
Bacteria
Protists
Fungi
Microorganisms are the most abundant organisms on earth.
Favourable conditions = sufficient food, moisture and optimum temp.
Are microorganisms harmful or not?
, 2
Most are harmless to plants/animals
Some cause diseases = pathogens
Most pathogens are parasites and live in or on other organisms
All viruses and some bacteria, protists and fungi are pathogenic in nature
Any diseases that is caused by a microorganism is known as an infectious disease
Historical Developments
Discovery of Viruses and Bacteria
Antonie van Leeuwenhoek (1632-1732)
Dutch lens maker, made the first microscope that could magnify objects 275x
1676
& observed microorganisms for the 1st time.
Scientists still believed that worms and midges originated from decomposing
meat (‘spontaneous creation’).
Edward Jenner (1729-1823)
Introduced vaccination as treatment for small pox, a viral disease.
1796
Louis Pasteur (1822-1895)
German chemist, developed heating process called pasteurisation (destroyed
1862
bacteria).
Pasteur described some pathogenic bacteria but also discovered the useful
role of bacteria in milk, yoghurt, vinegar etc.
He developed Jenner’s ideas and inoculated using weakened strains.
Robert Koch (1834-1910)
German physician, proved that bacteria caused disease.
In 1876, Koch described the anthrax bacillus and later he also discovered the
1876
bacteria that cause cholera and tuberculosis.
His work formed the basis of microbiology and pathology.
He also developed a staining technique for studying bacteria under a
microscope.
Alexander Fleming (1881-1955)
Scottish biologist discovered the penicillin mould which led to the production
1928
of an effective antibiotic, penicillin, to destroy bacteria.
Fleming shared 1945 Nobel Prize for medicine for his work on penicillin with
two other scientists (Florey and Chain)
Viruses
Basic Structure Of Viruses
Very small (20 nm – 450nm in diameter) and simple in composition.
Consists of a central nucleic acid surrounded by a protein capsule.
Can infect plants, animals or bacterial cells.
Viruses contain DNA or RNA (not both).
Some viruses (like the flu & HIV) are enclosed by a sheath of lipid and protein molecules. This
sheath originates from the host cell’s outer membrane.
Acellular and have no nucleus, cytoplasm or organelle.
The shape varies from simple to complex.
General Characteristics Of Viruses
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