What is Science?
Science
• What comes to mind when you hear the
word science?
Science
• What comes to mind when you hear the
word science?
Science
Science
• All science begins with a testable idea.
idea
• This in turn, leads to an experiment!
Spontaneous Generation
• Spontaneous generation is the theory that
life “arises” from nonliving matter
• In other words
words, over time
time, a “brick”
brick can
give rise to “life”.
• This
Thi was b
believed
li
d ffor centuries.
t i
– Mold came from bread.
– Beetles mysteriously appeared on waste
– And maggots appeared from meat
Spontaneous Generation
• Recipe for Bees (pg
(pg. 8)
– Kill a bull during the first thaw of winter
– Build a shed
– Place the dead bull on branches and herbs
inside the shed
– Wait for summer. The decaying body of the
bull will produce bees
bees.
Redi’s
Redi
s Experiment
• In 1668
1668, Francesco Redi had the idea that
spontaneous generation may be incorrect.
• He considered the possibility with maggots
and meat.
– Redi
R di th
thought,
ht perhaps,
h
th
thatt fli
flies llaid
id “i
“invisible
i ibl
eggs”.
Redi’s
Redi
s Experiment
• Redi decided to test his idea
idea.
• First, he identified what it was he wanted
to test.
test
– Redi wanted to test the idea of spontaneous
generation
• Next he took a guess, a hypothesis, at
what
h t he
h would
ld fifind.
d
– Redi hypothesized the possibility that flies laid
eggs too
t smallll tto see.
Redi’s
Redi
s Experiment
• Next he designed a test
test, or an
experiment.
On one side he had
jjars of meat left open
p
to the environment
On the other side he
had jjars of meat tightly
g y
sealed.
Redi’s
Redi
s Experiment
On one side he had
jars of meat left open
to the environment
Controlled Variable (Left
The Same/Comparison))
On the other side he
had jars of meat tightly
sealed.
Maniuplated Variable
(Variable Being
Manipulated)
Redi’s
Redi
s Experiment
• After some time
time, Redi recorded the results
of his test.
Redi’s
Redi
s Experiment
• He then drew a conclusion from his data
data.
– As the sealed jars didn’t grow flies,
spontaneous generation did not take place!
– Therefore, it was possible that flies laid eggs
too small to see.
Needham’s
Needham
s Test
• Of course
course, science and results must be
repeatable by others.
• Neeham conducted a test to verify Redi’s
Redi s
resuls.
• Instead
I t d off meatt though,
th
h Needham
N dh
used
d
gravy, heating a sealed flask.
• After a few days, Needham found
microorganisms in the gravy.
Who Was Right?
• To a certain extent
extent, both Needham and
Redi were right.
• Spallanzani expanded upon Needham’s
Needham s
test by heating the gravy flask longer than
Needham did
did.
Spallazani’s
Spallazani
s Test
Pasteur’s
Pasteur
s Test
Scientific Theory
• Further experiments would disprove
spontaneous generation and instead
support the cell theory of life
life.
• Although this took many, many
experiments!
The Scientific Method
• Although we call it the “scientific”
scientific method,
method
we use the steps to solve many types of
problems.
problems
• These steps are…
– Identify
Id tif the
th problem/ask
bl / k a question
ti
– Form a hypothesis
– Set
S up an experiment
i
– Record and analyze results
– Draw a conclusion
The Scientific Method
• Over time
time, if a hypothesis/explanation is
supported by many experiments, we can
call it a “theory”
theory .
• Think of a theory as a hypothesis on
steroids .
“steroids”
• Talk with a neighbor. What theories can
you think
thi k of?
f?
Steps in the Scientific Method