BIOLOGY IN FOCUS
PATTERNS IN NATURE
Chapter 1 Cells and the cell theory
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PRELIMINARYCOURSE
The impact of technology on the development of the
cell theory
■
use available evidence to assess the impact of technology,
including the development of the microscope, on the
development of the cell theory
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page 80
Table 1.2 The impact of technology on knowledge and understanding
TECHNOLOGY
(Identify
Identify technology and outline its uses and limitations)
THEN
NOW
PRIOR to: the proposal of the cell theory:
CURRENT: technology (outline
outline four ways in which
microscopes and specimen preparation have
improved)
PAST: at the time of the proposal of the cell
theory
IMPROVEMENT (advance) in technology:
KNOWLEDGE AND UNDERSTANDING
THEN
PRIOR to: the cell theory
NOW
CURRENTLY:
PAST: at the time of the proposal of the cell
theory
IMPROVEMENT in (progressive accumulation of) knowledge and understanding:
continued . . .
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Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
PUTTING IT ALL TOGETHER
Explain how the advance in technology allowed the progressive accumulation of knowledge and
understanding of the cell theory.
(Show the relationship between the improvement of the microscope and the increased knowledge
and understanding about the cell theory.)
Assess the impact of technology on the development of the cell theory.
(Generic conclusion—adjust this to suit the specific topic:
Scientists of the time were limited in their research by the technology available to them.
As equipment and techniques became more sophisticated, they could collect new evidence, leading
to new biological views/theories.
Therefore new technology had a great impact on the development of this theory—without the
advances in technology, the current knowledge and understanding would not have been possible.)
2
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
Answers
Table 1.2 The impact of technology on knowledge and understanding
TECHNOLOGY
(Identify
Identify technology and outline its uses and limitations)
THEN
NOW
PRIOR to the proposal of the cell theory:
■ magnifying glasses—lenses of poor quality
■ no microscopes.
CURRENT: technology (outline
outline four ways in which
microscopes and specimen preparation have
improved)
PAST: at the time of the proposal of the cell
theory
■ From the end of 16th to the end of
17th century—very basic compound
microscopes:
—Janssen’s hand-held tube with two lenses
—Hooke’s improved version with fine
adjustment and light source
—Van Leeuwenhoek’s high quality lenses in
simple microscope magnified up to 150 ×,
but the technology was lost when he died
■ At first, scientists were suspicious of
‘artificial images’ produced by microscopes
that distorted images:
—200 years after the discovery of the
microscope, optics microscopes with
achromatic lenses (1824) were in use.
Images were no longer distorted; precise
focusing screws
—were accepted as valid scientific
instruments
—cell theory idea arose and was proposed
in 1838–1839
■ Specimen preparation:
—specimens were cut very thinly by hand
—in the 1770s they began to use stains.
(Any four):
■ By 1870s further improvements included oil
immersion lenses, magnified up to 1500 ×
(similar to our school microscopes in
magnification and resolution)
■ 1933 Ernst Ruska built the first transmission
electron microscope that could magnify up to
12 000 ×. Much greater magnification and
resolution allowed more detail to be seen.
■ Microscopes today:
—light microscopes have high resolution
and magnification (up to 2000 ×) and
improvements such as phase contrast and
confocal microscopes have been developed
—microscopes are linked up to computers,
with software to improve the images seen
and some even allow three-dimensional
views to be built up
—synchotrons are being built with even
greater magnification and resolution
—specimen preparation. Major advances
have been made, including microtomes
and ultramicrotomes for very thin
sectioning, and good fixation and staining
techniques to keep artefacts to a minimum
and enhance visibility and contrast in
specimens.
IMPROVEMENT (advance) in technology:
Technology has advanced from simple magnifying lenses which magnified five times, beyond the
first hand-held tube version of a compound microscope to microscopes with their own light source,
adjustment screws and focusing knobs. Even greater magnification and resolution were achieved
when the lens quality improved and with the use of oil immersion. When the limitations of the
wavelength of light became restrictive, electron microscopes were invented to give increased
magnification and resolution—12 000 × in the 1930s and up to 1 million times today.
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Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
KNOWLEDGE AND UNDERSTANDING
THEN
NOW
PRIOR to the cell theory
Theory of spontaneous generation accepted,
but was challenged in the late 1600s (e.g. by
Francesco Redi and his 1668 experiment).
PAST: at the time of the proposal of the cell
theory
■ 1665: Robert Hooke studies cork and
introduces the term ‘cell’’
■ 1674–1683: Van Leeuwenhoek describes
‘animacules’ and ‘globules’ in tadpole eggs
(did he see bacteria and cells?)
■ 1801: Robert Browne discovered that each
cell had a nucleus
■ 1838: Schwann and Schleiden confirmed
their studies of the regular placement of
nuclei in a compartmental manner in both
plants and animals. The cellular basis of living
things was discovered and the cell theory
was proposed
■ 1855: Virchow proposed that cells only
arise from pre-existing cells
■ 1860s: Fleming, using synthetic dyes,
described and named chromatin material;
chromosomes discovered and named in
1888.
CURRENTLY:
■ Ultrastructure of cells can now be studied,
giving much greater knowledge and
understanding of the detail of the structure
(and therefore functioning) of sub-cellular
structures such as organelles
■ Synchotrons will even allow studies at the
molecular or atomic level.
IMPROVEMENT in (progressive accumulation of) knowledge and understanding:
Progress was made from the theory of spontaneous generation in past times, to the idea of cells
being the basis of living things (the cell theory). Further advances have revealed the structure and
functioning of not only cells, but also of the components of cells such as cell organelles. The future
will allow us to validate current theories about the chemical nature of cell components.
PUTTING IT ALL TOGETHER
Explain how the advance in technology allowed the progressive accumulation of knowledge and
understanding of the cell theory.
(Show the relationship between the improvement of the microscope and the increased knowledge
and understanding about the cell theory.)
Introduction—general statement
Scientists of the time were limited in their research by the technology available to them.
As equipment and techniques became more sophisticated, they could collect new evidence, leading
to new biological views/theories.
Body—detail
Evidence of some advances in technology and their direct effect on knowledge and understanding
to support the statement. Students should analyse material and attempt to determine the links by
looking at the sequence of events (dates), for example the invention of the microscope followed by the
discovery of cells; microscopes improved with light source and adjustment screws then the nucleus
was described; achromatic lenses led to better acceptance by the scientific community and then the
cell theory was proposed; specimen preparation techniques improved with the use of stains and then
chromatin and chromosomes were discovered.
Assess the impact of technology on the development of the cell theory.
Conclusion
Therefore new technology had a great impact on the development of this theory—without the
advances in technology, the current knowledge and understanding would not have been possible.
(Note the ‘judgment’ = assessment at the end.)
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Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.