Spontaneous Generation
Florida Sunshine State Standard Benchmark: SC.H.1.3.1 – The student knows
that scientific knowledge is subject to modification as new information challenges
prevailing theories and as a new theory leads to looking at old observations in a new
way.
Background Information:
(Portions reprinted with the permission of authors D. B. Fankhauser and J. Stein
Carter. URL http://biology.clc.uc.edu/courses/bio114/spontgen.htm)
Today we take many things in science for granted. Many experiments have been
performed and much knowledge has accumulated that people weren’t always aware
of. For centuries, people based their beliefs on their interpretations of what they
saw going on in the world around them without testing their ideas to determine the
validity of these theories — in other words, they didn’t use the scientific method
to arrive at answers to their questions. Rather, their conclusions were based on
untested observations. In the public eye, controversy is considered an act that
illustrates that a response is needed or that the "new" claims are inadequate
because they cannot "prove" anything. It is important to remember that SCIENCE
NEVER PROVES anything! Only models are disproved. One selects among the
alternative explanations (models) and may feel highly confident that one is
"correct" and then use supporting scientific evidence to support the conclusion.
Timeframe: 1-2 hours
Materials
Computer with Internet access; and/or library access
Colored pencils or markers
Poster board
Worksheet
Scissors
Teacher Procedure:
1. Students will read the Overview provided above.
2. Present the following observations (without conclusions) to students.
3.
4.
5.
6.
7.
8.
9.
10.
Observation: Every year in the spring, the Nile River flooded areas of
Egypt along the river, leaving behind nutrient-rich mud that enabled the
people to grow that year’s crop of food. However, along with the muddy
soil, large numbers of frogs appeared that weren’t around in drier times.
(Conclusion: It was perfectly obvious to people back then that muddy
soil gave rise to the frogs.)
Observation: In many parts of Europe, medieval farmers stored grain in
barns with thatched roofs (like Shakespeare’s house). As a roof aged, it
was not uncommon for it to start leaking. This could lead to spoiled or
moldy grain and, of course there were lots of mice around.
(Conclusion: It was obvious to them that the mice came from the
moldy grain.)
Allow students to brainstorm their own conclusions.
One student will be assigned to list all student-generated conclusions on
the board or poster paper.
Read aloud to students the following recipes for bees and mice.
Recipe for bees:
Kill a young bull and bury it in an upright position so that its horns
protrude from the ground. After a month, a swarm of bees will fly out
of the corpse.
Jan Baptista van Helmont’s recipe for mice:
Place a dirty shirt or some rags in an open pot or barrel containing a
few grains of wheat or some wheat bran, and in 21 days, mice will
appear. There will be adult males and females present, and they will be
capable of mating and reproducing more mice.
Allow students to suggest plausible explanations for the publishing of
these recipes.
Place students into groups of 4 or 5 students.
Each group will research the subject of spontaneous generation using
either the Internet or library resources.
Provide the following URL ,
http://www.kent.k12.wa.us/staff/rlynch/sci_class/chap01/spontaneous.
html, as a main source of information as well as providing a worksheet for
documenting knowledge gained through research.
Provide the following URL,
http://biology.clc.uc.edu/courses/bio114/spontgen.htm for a detailed
explanation as well as more observations and conclusion activities.
11. Each group must complete the following:
a. Either a timeline, graphic organizer or a freeform map of events
leading to the disproving of spontaneous generation, including names,
dates, pictures, and illustrations.
b. An essay based upon the following statement:
Louis Pasteur was a very important scientist in the understanding
of Spontaneous Generation. One very important point to note is
that Pasteur did not seek to find an answer to the broad
question,
“Has spontaneous generation ever occurred?”
Write an essay on whether or not spontaneous generation has
ever occurred.
Assessment:
The students will be evaluated according to the amount of effort, their specific
job performance, participation within the team, and on the final product (timeline,
graphic organizer or freeform web.). For scoring, use rubrics which may be found
at the following URL,
http://school.discovery.com/schrockguide/assess.html#rubrics
Home Learning:
Completion of the timeline, graphic organizer or freeform map and essay, which
may include research, drawings, or writing.
Extensions:
1. Students will research Pasteur’s experiment and then carry out a
recreation of his experiment.
2. Students will investigate life on Mars and submit a report on their
findings.
3. Student will research the work of Oparin, Haldane, and Stanley Miller. A
freeform map demonstrating their significant accomplishments will be
created.