Scientific Method
and
Graphing
p g
Spontaneous Generation
• Living things come from nonliving things
• Believed for a very long time
• Why would people believe this?
Maggots come from meat???
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Historical Experiments
1668 – Francesco Redi rejected the hypothesis of
spontaneous generation with his hypothesis that
flies produce maggots
Redi’s Experiment
p
Historical Experiments
Mid 1700s – John Needham claimed that
spontaneous generation could occur
under the right conditions
Historical Experiments
• Mid 1700s – Larraro Spallanzani improved Needham’s
experiment by sealing the flask
Historical Experiments
• 1864 – Louis Pasteur settled the spontaneous
p
generation argument by creating a flask that had a
long curved neck allowing air into the flask
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The Scientific
Method involves a
series of steps
p
that are used to
i
investigate
sti t a
natural
occurrence.
We will
ll take
k a
closer look at
these steps and
the terminology
you will need to
y
understand
before you start
a science
project.
j t
1.
2.
3.
4.
5.
6.
7.
8.
Steps of the
Scientific Method
1. State the Problem/Question:
Q
Develop a question or problem
th t c
that
can
nb
be ssolved
lv d through
thr u h
experimentation.
p m
.
Example:
2. Do research about the problem:
Do research on your topic of
interest.
Example:
Do y
you remember the
next step?
3.Make a Hypothesis
yp
Predict a possible answer to the
problem or question.
question
E mp
Example:
4. Design and perform a Controlled Experiment:
A controlled experiment
p
must test only
y __ f
factor.
The factor that is tested is the ____________.
The part of the experiment that contains the variable
is called
ll d the
th _______________.
Another part of the experiment is done that is the
same in every way except it does not contain the
variable.
This part of the experiment is called the _________.
In a scientific experiment, the control is the group
that serves as the standard of comparison.
The part of the experiment that does not contain the
variable is called the _____________.
Example: What is the factor we want to test?
Variable:
Experimental Group
Group:
Control Group: People who do not get the “Miracle
Pill”. They take a pill that looks exactly like the
“Miracle
Miracle Pill
Pill”. This is called a Placebo.
Placebo
How long will your experiment go on for?_____
How many people will be in your experimental
group? ______
How many people will be in your control group?
_____
What age group of people will participate in your
experiment?
p
___________
When will the people in your experiment take the
Pill the are given?_______________
Why is everything
Wh
thin in the
th experiment
xp im nt
exactly the same except whether or not
th are taking
they
t kin the
th “Mi
Miracle
cl Pill”?
Independent Variable
The independent,
independent or manipulated
variable, is a factor that’s
intentionally varied by the
experimenter.
Wh making
When
ki a graph
h the
th independent
i d
d t variable
i bl
goes on the ______________ .
Example:
E
l Whether
Wh th or nott the
th
people
p
p in the experiment
p
got
g the
“Mi
“Miracle
l Pill”
Dependent Variable
The dependent
dependent, or responding
variable, is the factor that may
change as a result of changes made
in the independent variable.
variable
The dependent variable always goes
on the Y-axis.
Example:
5.Collect Data
Data or observations are recorded.
Observations can include mathematical
measurements, as well
ll as observations
b
i
made with the senses or with scientific
instruments.
instruments
Example: The people participating in the
experiment
p m
will fill
f out a chart that asks
them to evaluate their skin, hair, nails,
muscle tone etc.
Y will
You
ill organize
i your d
data
t by
b iincluding
l di
tables, graphs, and photographs.
Results of questions answered by
participants
ti i
t iin experiment
i
t after
ft 30 d
days.
Experimental Group
Control Group
Does your hair feel
lik it did 10 years
like
ago?
1
0
Do your nails feel 10
years younger?
0
2
Does y
your skin look
like it did 10 years
ago?
1
1
Does your muscle
tone feel like it did
10 years ago?
2
1
6. Analyze Results
6
Example: Study the data and
determine if their was any
major difference in how the
Experimental Group felt
compared to how the Control
Group felt at the end of the
experiment.
7. Form a Conclusion:
7
Include a statement that
accepts or rejects the
hypothesis.
Ex mpl : Th
Example:
The “Mi
Miracle
l Pill” d
doess
not work.
wor . The
h following
fo ow ng data:…
ata …
8. R
8
Repeat
p t th
the experiment
xp im nt
You must p
perform the
experiment again. You must get
the same results again.
g
If you
y
d not get the
do
h same results
l
again
g
you
y must work on your
y
experimentall procedure.
d
Other
h
scientists must be able to
perform
f
your experiment and
d
get the same results.
g
Put the following steps of the scientific
method in the proper order:
A. _____ organize and analyze data
B _____ State
B.
St t a hypothesis
h
th i
C. _____ identify the problem
D. _____ State conclusion
E. _____ design
g and carry
y out an
experiment
F. _____ Make observations and
record data
G. _____ gather information
Think yyou can name all
eight steps?
Collect
State
Experiment
the
Data
Problem/Question
and
Analyze
Data
Repeat
DoFormulate
Research
Conclusion
the experiment
a Hypothesis
Once a scientific hypothesis
meets the test of repeated
experimentation it becomes a
Theory.
A Scientific Law is a statement that
summarizes the results of many
observations and experiments.
experiments
Difference between a Law and a Theory?
___________- tells what happens
___________-- our attempt to explain why
it happens
Graphing
To study data more easily, science researchers
record
d laboratory
l b
t
observations
bs
ti ns and
nd
measurements in an organized manner. This
careful method of organization helps
researchers
h
visualize
i
li data
d t and
dh
helps
l them
th
reach more accurate conclusions.
Three common methods used to record
observations:
• Bar graphs
• Data
D t tables
t bl
• Line graphs
Bar Graphs
A bar graph allows the scientist to
compare data.
Interpreting a Bar Graph
Data Table
The data table is used to record numerical data.
The information is organized by arranging
observations in columns with appropriate
pp p
headings.
Year
Amount of
Rain (inches)
Bushels of
Grain per
Acre
1979
13
60
1980
7
50
1981
10
65
1982
9
60
1983
11
70
1984
15
20
1985
12
65
Rearrange the data in the table completing both
Columns of the data table provided, so the values of
Amount of
Rain (inches) are increasing from the top of the table to
the bottom.
Amount or
Rain
(inches)
Bushels of
Grain per
Acre
Interpreting a Data Table
Line Graph
•
•
•
•
A line graph is used to show relationships between 2 variables.
One variable, called the independent variable, is placed along the
horizontal (bottom) or X
X-axis
axis.
The other variable, the dependent variable, is placed on the vertical
(side), or Y axis.
The data for the dependent variable depends on the changes in the
independent variable.
3.0
3.6
4.0
3.0
3.6
4.0
Timeline of Events
Year
Event
1668
Francesco Redi attacks spontaneous generation and disproves it for large organisms
1745
John Needham adds broth to a flask and boils it, lets it cool and waits.
Microbes grow and he proposes it as an example of spontaneous generation.
1768
Lazzaro Spallanzani repeats Needham's experiment, but covers the flask after boiling.
No growth occurs.
1859
Louis Pasteur's swan-neck flasks show that spontaneous generation does not occur.
1870
Thomas H. Huxley gives his "Biogenesis and Abiogenesis" lecture.
The speech offered powerful support for Pasteur's claim to have experimentally disproved
spontaneous generation.
1877
John Tyndall publishes his method for fractional sterilization, showing the existence of
heat-resistant bacterial spores.