CAMPBELL
BIOLOGY
How do we study science?
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
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 First a scientist identifies a problem or question
 Why do certain cells turn into cancer cells?
 Is this substance hazardous to your health?
 Make Observations
Scientific Inquiry
Dr Burns
NVC
 Then the scientist formulates a hypothesis
 Then the scientist designs an experiment to
study the problem
© 2014 Pearson Education, Inc.
Scientific Method
1. Observation – Observe some aspect of nature
2. Investigate what others have found, ask critical
questions
Scientific Method
1. Observation – Observe some aspect of nature
3. Develop a hypothesis – educated guess to make a
prediction
4. Design experiments to test your predictions
5. Repeat experiments
6. Analyze the data
7. Draw conclusions
8. Report the method, data, results and conclusions
Scientific Method
2. Investigate what others have found, ask critical
questions
Scientific Method
3. Develop a hypothesis
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Hypothesis
A hypothesis is a possible explanation for an
observation.
Hypothesis
 Are there some questions that can not be
answered by science?
A hypothesis
-must be tested to determine its validity
-is often tested in many different ways
-allows for predictions to be made
Experimental Design
 Search the available databases to find out
what other scientists have done, how they did
their research and their results.
 Design the experiment to test one variable at
a time.
 Set up a control group which is identical to
the experimental group except without the
one variable being tested.
 Repeat the experiment to get statistically
significant data.
Controlled experiments
 Constants – all the factors that are kept the
same in the experiment
 Control Group and Experimental Group – all
the constants are the same, only the
independent variable differs between the two
groups
Controlled experiments
 A independent variable is something that is
changed to see how that change effects the
study.
 How many variables should you test at one time?
 The dependent variable is measured, it may
change as a result of the independent variable
Example
 Hypothesis: Artificial sweeteners are safe to
eat
 The researchers choose the mouse as a model
to test the safety of the additive (Why not
humans? Are mice good models?)
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Example
 They divide a group of similar mice (all the
same age, sex, raised the same way) into two
groups.
 Half the animals are the control group, they are
fed the normal diet, the other half are the
experimental group = they are fed a diet of
50% normal food and 50% artificial sweetener
(Is this a lot?)
Results
 One third of the test group developed bladder
cancer
 None of the control group developed bladder
cancer.
 Cannot accept the hypothesis that the additive
is safe at this level of consumption.
Does Smoking Cause Cancer
 One way to study a problem is to look at
epidemiology evidence.
 Look at cancer rates over time, correlate
cancer rates with events and changes that
also occur during that period.
 What would have happened if we had looked
at a different dependent variable, hyperactivity,
would we have missed the bladder cancer?
Theories in Science
 In the context of science, a theory is
 Broader in scope than a hypothesis
 General, and can lead to new testable hypotheses
 Supported by a large body of evidence in
comparison to a hypothesis
© 2011 Pearson Education, Inc.
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Figure 1.21a
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