Name: _________________________________________
Date: _________________________
Aim #3: How can we use the scientific method to understand the world around us?
Textbook Pgs: 6-13
I.
What is the Scientific Method?
1. The scientific method begins with Scientific Inquiry = The diverse ways in which scientists
study the __________________________ and propose _________________________ based on the
_________________________ they gather
2. Scientific Method: an organized set of __________________________________________________
II.
Scientific Method Example: Let’s go back a few years…
Long ago, many people believed that living things could come from nonliving things. They
thought that worms came from wood and that maggots came from decaying meat. This idea was
called spontaneous generation. In 1668, an Italian biologist, Francesco Redi, did experiments to prove
that maggots did not come from meat.
Redi placed pieces of meat in several jars. He divided the jars into three groups:
• He left the first group uncovered with meat in it.
• He covered the second group of jars with a fine cloth so only air could get in.
Conclusion: Redi observed the jars for several days. He saw flies on the cloth of the covered jars but no
flies in the jar), and he saw flies laying eggs on the meat in the uncovered jars. Maggots appeared only
on the meat in the group of jars left uncovered.
1. What was the problem in Redi’s experiment?
a. How do maggots appear in meats?
b. How do worms appear in wood?
c. Is spontaneous generation a valid explanation for
maggots in meats?
d. All of the above are examples of problems.
2. What do you think his hypothesis was?
a. Maggots grow through spontaneous generation.
b. Maggots come from eggs laid by flies.
c. Maggots find their way into woods and meats.
d. The problem cannot be solved.
3. How did he test his hypothesis?
a. He placed food in two jars, covering one jar and leaving the other uncovered.
b. He placed food in two jars and left both jars uncovered.
c. He placed food in two jars and covered both jars.
d. He put food in one jar and no food in a second jar.
4. What was the variable in his experiment?
a. Covering both jars.
b. Covering one jar and leaving the
other uncovered.
c. Leaving both jars uncovered.
d. There was no variable in this experiment.
5. What do you think Redi’s conclusion was?
a. Living things come from other living things.
b. Living things are created through
spontaneous generation
c. He did not have enough data to make a
Conclusion
III. What are the steps to the Scientific Method?
1. Identify the _________________
4. Test the _____________________
2. Gather _____________________
5. Collect ____________
3. State a _____________________
6. State a _____________________
III.
What are the components of a controlled experiment?
•
Controlled Experiment: An experiment that tests the effects of _____________________________
•
Why is it important that we only test the effects of ONE VARIABLE? Answer Below
1. Variables: A factor that can ________________________________ in the results of an experiment.
i. Independent Vs. Dependent Variable
Independent Variable
• A.K.A the _______________________
variable.
Dependent Variable
• A.K.A the ___________________________
variable.
• The variable that “I” _______________
• The variable that is _____________________
• The “_____” in your hypothesis
• The “___________” in your hypothesis
Ex: If I add fertilizer to the soil, then plants
Ex: If I add fertilizer to the soil, then plants will
will grow taller
grow taller
ID =
DV =
ii. Controlled Variables (Constants) variables that need to ______________________________
so they don’t affect the results
Ex: Plants receive the same amount of water/soil, same plant type used, pot size is the same
2. Control Group and an Experimental Group
Control Group
• Used for _______________________
• Under ________________________ conditions
Experimental Group
• Receives the variable that is being
_____________________
• Does not receive ___________________ being
tested
Ex: 5 plants kept in the classroom with the same
Ex: 5 plants kept in the classroom with the
soil type and type of plant under normal light,
same soil type and type of plant under normal
water and temperature conditions as the
light, water and temperature conditions as the
experimental group. BUT they do NOT receive
plants in the control group.
treatment = fertilizer
BUT they receive treatment = fertilizer
Practice Identifying the Variable:
QUESTION
Mary wants to find out whether
plants produce more leaves when
grown in red, blue or green light
INDEPENDENT VARIABLE
DEPENDENT VARIABLE
Tom wonders whether the speed
of his model train affects the
amount of time it takes the train to
stop
Christine is studying the pressure
in a closed container at different
temperatures
John is trying to determine
whether basketball players have
lower blood pressures than people
who don’t play basketball
Janet is doing an experiment to see
if the number of peanuts produced
per plant changes when the
amount of fertilizer given to plants
is changed
Teresa wants to see if different
brands of yeast make her loaves of
bread rise to different heights
Read the following and answer the questions below:
Many people who are in favor of alternative medicine claim that large doses of vitamin C introduced into
a vein speed up the healing of surgical wounds. Describe an experiment to test this hypothesis. In your
answer include:
o The difference between the experimental group of subjects and the control group
o Two conditions that must be kept constant in both groups
o Data that should be collected
o An example of experimental results that would support the hypothesis
IV.
How do we organize and analyze data?
Recording and analyzing data are very important steps. Logically organizing data allows us to
formulate a conclusion and state whether or not our hypothesis was supported or rejected.
1. _________________ show relationships in our data. They also allow us to make predictions
2. _________________ organizes our data throughout the experiment. Graphs can be created using
information from a data table
V.
What are characteristics of a good experiment?
1. Can be ______________________ the same way and get the same results
2. Have a _________________ sample size and ______________ test subjects
3. Performed over a ______________ period of time
4. Only __________ variable is tested while all other characteristics _________________
5. Are _____________________ and examined by other scientists to determine its accuracy
6.
The hypothesis must be ____________________
7.
It is ____________________ and unbiased. Fact and opinion should not be mixed.
Bias occurs when what the scientist expects changes how the results are viewed.
8.
The experiment follows standards that are _________________ and __________________