Summary microorganisms Life sciences.Grade 11 IEB, 3 In 1, ISBN: 9781920686543 Life Sciences (Biology)

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Microorganisms
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?

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 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