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198 SCIPAD - BIG IDEAS - BOOK 2
LIFE OF MICROBES
Introduction to Microorganisms
Microorganisms are living things that are only visible with the use of a microscope.
The study of microorganisms is called microbiology. Microbiology involves culturing them (growing
large numbers) in controlled laboratory conditions so we can research them and find out how
they survive. This helps us to learn which are useful to us and about those that can harm us.
Microorganisms can be divided into a number of groups including bacteria, fungi and viruses.
The majority of microorganisms help us survive by doing things such as assisting with digestion,
recycling chemical elements (e.g. carbon, nitrogen, sulfur, etc.) in the environment, and by
decomposing (breaking down) dead organisms.
Some species of microorganisms can cause infectious diseases. Disease causing microorganisms
are called ‘pathogens’. They may breed quickly and overwhelm the immune system, or they may
produce powerful toxins that interfere with bodily functions. Viruses inflict damage by replicating
inside living cells, thereby damaging or destroying the host cells.
Because microorganisms are so small, scientists measure them using a unit call a micrometre (µm)
which is 1/1000 of a millimetre. However, even this very small unit of measurement is sometimes
inadequate. For example, viruses are generally measured in nanometres (nm) which are 1/1000
of a micrometre.
1. Define the term ‘microorganism’:
2. Describe the job of a microbiologist:
3. Outline why we study microorganisms:
4. Define the term ‘pathogen’:
5. Outline two ways bacteria can cause disease:
(a)
(b)
6. Complete the following table.
Millimetre (mm) Micrometre (mm) Nanometre (mm)
1
Human hair
50 -180 µm
Red Blood cell
7 - 8 µm
E. coli bacterium
1 - 3 µm
Corona virus
0.1 - 0.5 µm
Phage virus
0.2 µm
The Relative Size of Bacteria and Viruses
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