Development of the Cell Theory
spontaneous
generation:
the theory
that life
could emerge
spontaneously
from non-living
matter
cell theory: the
theory stating
that all living
things are made
up of cells, the
smallest unit of
life, and that all
cells come from
pre-existing cells
The microscope provided the technology to explore the world of microscopic
organisms. Before the invention of the microscope, many people believed in
spontaneous generation—the emergence of life spontaneously from non-living
matter. With the invention of the microscope, scientists were able to show many
living organisms that could not be seen with the naked eye. The microscope also
showed details of cells and, therefore, led to the development of cell theory.
Spontaneous generation thrived until the nineteenth century. In the seventeenth
and eighteenth centuries, scientists performed a number of experiments that
disproved the theory of spontaneous generation; however, spontaneous generation
continued to be accepted.
Turn to pages 247 to 249 of the textbook and read the introductory paragraph
of “Development of the Cell Theory” and the information in “Spontaneous
Generation.”
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Copyright © 2005 Alberta Education
21
1. Who first proposed the theory of spontaneous generation?
2. How did Francesco Redi try to disprove the theory of spontaneous generation?
3. What was the manipulated variable in Redi’s experiment?
4. How did John Needham try to prove that living things could be produced from
non-living matter?
5. What did Lazzaro Spallanzani suggest was the cause of the growth in John
Needham’s flask?
6. How did believers of spontaneous generation try to discredit Spallanzani’s
ideas?
7. Describe the experiment Louis Pasteur performed to disprove spontaneous
generation.
8. What were Pasteur’s manipulated and responding variables?
Check
Check your answers with those on page 26.
A microscope can reveal a whole new world of organisms and structures that
cannot be seen with the naked eye. Organisms—like amoebas, stentors, and
euglena—as well as parts of a cell can be seen with a compound microscope.
The next activity involves preparing a wet mount slide. Before you do this
activity, it is a good idea to become more familiar with preparing a wet mount
slide. Insert the Science 10 Multimedia CD into your computer, and watch
“Segment 3: Preparing a Wet Mount and Observing a Specimen.”
For further information, you may also
refer to “Preparing a Wet Mount” on
page 480 of the textbook.
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Science 10 • Module 3 • Section 1
Copyright © 2005 Alberta Education
Inquiry Lab
Examining Pond Water
Turn to pages 250 and 251 of the textbook and read the entire activity. This
activity will allow you to become familiar with some of the organisms you can
see in pond water using a microscope.
You may refer to the following website to become familiar with various
organisms commonly found in pond water.
http://www.microscopy-uk.net/pond/index.html
You may also search for information by entering the
words microscopic organisms in pond water in one of
the Internet’s search engines or check
science reference books at your local library.
9. Name some organisms you think you will find in
pond water.
Check
Check your answer with the one on page 26.
If you have access to a supervised laboratory, do Part A. If you do not have
access to a supervised laboratory, do Part B.
Part A
Follow the steps outlined in the procedure on page 250. Pay special attention
to the safety precautions mentioned.
10. Draw a diagram of each organism you see and label it with the part of the
container the drop of water came from.
11. Answer the following on page 250 of the textbook.
a. questions 1 and 2 of “Analyzing and Interpreting”
b. question 3 of “Forming Conclusions”
Check
Check your answers with those on page 27.
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Copyright © 2005 Alberta Education
23
Part B
Insert the Science 10 Multimedia CD into your computer, and view the segment
“Pond Water.” Answer the following questions as you view the segment. You
may have to stop the segment or go back as you answer the questions.
12. a. What was seen when a drop of water was placed under the low-power
lens?
b. How do the organisms under the medium-power lens compare to those
under the low-power lens?
c. What happened to the organism when Protoslo was used?
d. What organism was seen in the water taken from the top of the
aquarium?
e. What organism was seen in the water taken from the middle of the
aquarium?
f. What organism was seen in the water taken from the bottom of the
aquarium?
13. Answer the following on page 250 of the textbook.
a. questions 1 and 2 of “Analyzing and Interpreting”
b. question 3 of “Forming Conclusions”
Check
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Check your answers with those on page 28.
Science 10 • Module 3 • Section 1
Copyright © 2005 Alberta Education
When viewing cells through a
microscope, you will see some of the
structures of the cell. Developments
and improvements in lens technology
has led to the realization that the cell
is an important part of living things.
Recognizing that cells and cell functions
are part of all living thing is known as
cell theory.
Turn to pages 251 and 252 of the
textbook and read “The Cell Theory.”
14. Who first proposed the cell theory
and why?
15. State the three main ideas of the cell
theory.
16. Which two types of organisms are
not part of the cell theory?
Check
Check your answers with those on page 28.
Looking Back
You have now covered all the concepts
for this lesson. You assessed the
influence of the microscope on the
development of cell theory.
17. Answer questions 1, 2, 5, and 8 of “Check and
Reflect” on page 252 of the textbook. Note: One
paragraph may be adequate to answer question 8.
Check
Go to ...
Check your answers with those on pages 28 and 29.
Go to pages 3 to 5 of Assignment Booklet 3A and answer questions 7 to 14.
Science 10 • Module 3 • Section 1
Copyright © 2005 Alberta Education
25
Glossary
cell theory: the theory stating that all living
things are made up of cells, the smallest
unit of life, and that all cells come from
pre-existing cells
spontaneous generation: the theory that
life could emerge spontaneously from
non-living matter
controlled variable: a condition that is held
constant throughout an experiment
Suggested Answers
1. Aristotle first proposed the theory of spontaneous generation in about 350 BC.
2. Francesco Redi tried to disprove the theory of spontaneous generation by showing that maggots
appeared when flies had access to meat and did not appear when flies could not access the meat.
3. The manipulated variable in Redi’s experiment was the flies’ access to the meat.
4. John Needham boiled chicken broth and put it in a flask and sealed it. Organisms still appeared
after a while in the chicken broth in Needham’s experiment. Since boiling was accepted as the
method of killing living organisms, Needham suggested that there was a life force that produced
spontaneous generation.
5. Lazzaro Spallanzani suggested that the organisms that grew in the flask came from the air that
was in the flask before Needham sealed it.
6. Believers of spontaneous generation said that all Spallanzani did was show that air was required
for spontaneous generation.
7. Louis Pasteur placed meat broth in a flask; then he heated and bent the neck of a flask into an
“S” shape. He then boiled the broth in the flask and allowed it to cool. He found that no moulds
grew in the broth, even after several years. Pasteur also showed that if the flask with the boiled
broth is tipped so the broth reaches the “S” bend, moulds would later appear in the broth.
8. Pasteur’s manipulated variable was the access of dust to the broth in the flask. His responding
variable was the ability to grow mould in the broth.
9. Answers will vary. Some organisms that may be found in pond water are amoebas, anabaenas,
nostoc, spirogyra, coleps, euglenas, parameciums, stentors, vorticellae, rotaria, and nematode
worms.
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Science 10 • Module 3 • Section 1
Copyright © 2005 Alberta Education