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Chapter 1: Scientific Thinking
Your best pathway to understanding the world
Lectures by Mark Manteuffel, St. Louis Community College
Learning Goals
• Describe what science is.
• Describe the scientific method.
• Describe key aspects of well-designed
experiments.
• Describe how the scientific method can be
used to help make wise decisions.
• Describe the major themes in biology.
More than just a
collection of facts,
science is a
process for
understanding the
world.
1.1 What is science?
What is biology?
Scientists
 Are
curious
 Ask questions about how the world works
 Seek answers
• Does the radiation released by cell phones
cause brain tumors?
• Are anti-bacterial hand soaps better than
regular soap?
• Do large doses of vitamin C reduce the
likelihood of getting a cold?
• Why is morning breath so stinky? And can
you do anything to prevent it?
• Why is it always windy on streets with tall
buildings?
• Does taking aspirin before drinking alcohol
lead to faster intoxication?
Science
 Not
simply a body of knowledge or a list
of facts to be remembered…
 …but
rather an intellectual activity,
encompassing observation, description,
experimentation, and explanation of
natural phenomena.
“How do you know that is true?”
The single question that
underlies scientific thinking
Dannon yogurt
• Claimed in nationwide advertisements that its
Activia yogurt relieves irregularity and helps with
“slow intestinal transit time.”
• Also claimed that its DanActive dairy drink helps
prevent colds and flu.
• The FTC charged that the ads were deceptive and
had no substantiation or scientific evidence.
…the importance of questioning the truth of many
“scientific” claims you see on merchandise packages
or read in the newspaper or on the internet.
Can we trust the packaging
claims that companies make?
Clinical drug trials and evidence
CEO says: people “are really not scientifically
minded enough to be able to understand a
clinical study.”
The most important questions in
biology:
 What
is the chemical and physical basis for
life and its maintenance?
 How
do organisms use genetic information
to build themselves and to reproduce?
The most important questions in
biology:
 What
are the diverse forms that life on
earth takes and how has that diversity
arisen?
 How
do organisms interact with each
other and with their environment?
Scientific Literacy
 how
to think scientifically
 how to use the knowledge we gain to
make wise decisions
 increasingly important in our lives
 literacy in matters of biology is especially
essential
Take-home message 1.1
 Through
its emphasis on objective
observation, description, and
experimentation, science is a pathway by
which we can come to discover and better
understand the world around us.
1.2 Biological literacy is
essential in the modern
world.
A brief glance at any newspaper will
reveal 
 Why
are unsaturated fats healthier for you
than saturated fats?
 What
are allergies? Why do they strike
children from clean homes more than
children from dirty homes?
 Why
do new agricultural pests appear
faster than new pesticides?
Biological Literacy
The ability to:
1. use the process of scientific inquiry to
think creatively about real-world issues,
2. communicate those thoughts to others,
and
3. integrate them into your decisionmaking.
Take-home message 1.2
 Biological
our lives.
 To
issues permeate all aspects of
make wise decisions, it is essential for
individuals and societies to attain
biological literacy.
1.3 The scientific method is
a powerful approach to
understanding the world.
Why and when do people
develop superstitions?
Can animals be superstitious?
Understanding How the World
Works
 Someone
wonders about why something
is the way it is and then decides to try to
find out the answer.
 This
process of examination and discovery
is called the scientific method.
The Scientific Method

Observe a phenomenon

Propose an explanation for it

Test the proposed explanation through a
series of experiments
↓
Accurate & valid,
or…
Revised or alternative explanations proposed
Scientific Thinking Is Empirical…
…based on experience and observations
that are rational, testable, and repeatable.
Take-home message 1.3
 There
are numerous ways of gaining an
understanding of the world.
 Because
it is empirical, rational, testable,
repeatable, and self-correcting, the
scientific method is a particularly effective
approach.
A beginner’s
guide:
what are the
steps of the
scientific
method?
1.4 Thinking like a scientist:
how do you use the scientific
method?
“Scientific Method”
A
rigid process to follow?
 A “recipe”?
 An adaptable process?
 One that includes many different
methods?
The basic steps in the scientific method are:
 Step
1: Make observations.
 Step 2: Formulate a hypothesis.
 Step 3: Devise a testable prediction.
 Step 4: Conduct a critical experiment.
 Step 5: Draw conclusions and make
revisions.
Q
What should you do
when something you believe
in turns out to be wrong?
This may be the most important feature of
the scientific method:
it tells us when we should change our minds.
The scientific method can be used to
examine a wide variety of issues.

Does echinacea reduce the intensity or duration
of the common cold?

Does shaving hair from your face, legs, or
anywhere else cause it to grow back coarser or
darker?
Take-home message 1.4
 The
scientific method (observation,
hypothesis, prediction, test, and
conclusion) is a flexible, adaptable, and
efficient pathway to understanding the
world because it tells us when we must
change our beliefs.
1.5 Step 1: Make
observations.
Look for interesting
patterns or cause-andeffect relationships.
Does taking
echinacea reduce
the intensity or
duration of the
common cold?
Using the scientific method, we can
answer these (and other) questions:
 Does
hair that is shaved grow back
coarser or darker?
Take-home message 1.5
 The
scientific method begins by making
observations about the world, noting
apparent patterns or cause-and-effect
relationships.
1.6 Step 2: Formulate a
hypothesis.
A proposed explanation for
observed phenomena
To be most useful, a hypothesis must
accomplish two things:
1. It must clearly establish mutually
exclusive alternative explanations for a
phenomenon.
2. It must generate testable predictions.
Devising Testable Predictions
• We can only evaluate the validity of a
hypothesis by putting it to the test.
• Researchers often pose a hypothesis as a
negative statement, proposing that there
is no relationship between two factors
The Null Hypothesis

A negative statement that proposes that
there is no relationship between two factors

These hypotheses are equally valid but are
easier to disprove.

An alternative hypothesis

It is impossible to prove a hypothesis is
absolutely and permanently true.
Null and Alternative Hypotheses
 Echinacea
reduces the duration and
severity of the symptoms of the common
cold.
Or as a null hypothesis:
• Echinacea has no effect on the duration or
severity of the symptoms of the common
cold.
Null and Alternative Hypotheses
 Hair
that is shaved grows back coarser
and darker.
Or as a null hypothesis:
• There is no difference in the coarseness or
color of hair that is shaved relative to hair
that is not shaved.
Take-home message 1.6
A
hypothesis is a proposed explanation for
a phenomenon.
1.7 Step 3: Devise a
testable prediction.
Suggest that, under certain
conditions, we will make
certain observations.
Devising a Testable Prediction
from a Hypothesis

Keep in mind any one of several possible
explanations could be true.
Devising a Testable Prediction
from a Hypothesis
The goal is to:

Propose a situation that will give a particular
outcome if your hypothesis is true…

…but that will give a different outcome if your
hypothesis is not true.
Hypothesis: Eyewitness testimony is
always accurate.
 Prediction:
Individuals who have
witnessed a crime will correctly identify
the criminal regardless of whether multiple
suspects are presented one at a time or all
at the same time in a lineup.
Hypothesis: Echinacea reduces the duration and
severity of the symptoms of the common cold.
Hypothesis: Hair that is shaved grows back
coarser and darker.
 Prediction:
If shaving leads to coarser,
darker hair growing back, then if
individuals shaved one leg only, the hair
that grows on that leg should become
darker and coarser than the hair growing
on the other leg.
Take-home message 1.7
 For
a hypothesis to be useful, it must
generate a testable prediction.
1.8 Step 4: Conduct a
critical experiment.
an experiment that makes it possible
to decisively determine whether a
particular hypothesis is correct
Hypothesis:
Echinacea reduces the
duration and severity of
the symptoms of the
common cold.
Does shaving or cutting hair make it grow
back more thickly?
 Hypothesis:
Hair that is shaved grows
back coarser and darker.
 Critical
ideas?
experiment
Take-home message 1.8
A
critical experiment is one that makes it
possible to decisively determine whether a
particular hypothesis is correct.
1.9 Step 5: Draw
conclusions, make revisions.
Trial and error
The Role of Experiments
 What
is important is that we attempt to
demonstrate that our initial hypothesis is
not supported by the data.
 If
it is not, we might then adjust our
hypothesis.
Making Revisions
 Try
to further refine a hypothesis.
 Make
new and more specific testable
predictions.
Does echinacea help prevent the common cold?
Hypothesis: Echinacea reduces the duration and
severity of the symptoms of the common cold.
Hypothesis: Hair that is shaved
grows back coarser and darker.
Take-home message 1.9
 Based
on the results of experimental tests,
we can revise a hypothesis and explain the
observable world with increasing accuracy.
A
great strength of scientific thinking,
therefore, is that it helps us understand
when we should change our minds.
1.10 When do hypotheses
become theories?
Two distinct levels of
understanding that scientists use
in describing our knowledge
about natural phenomena
Hypotheses and Theories
A
hypothesis is a proposed explanation
for a phenomenon.
• a good hypothesis leads to testable
predictions.
Hypotheses and Theories
A
theory is a hypothesis for natural
phenomena that is exceptionally wellsupported by the data.
• a hypothesis that has withstood the test of
time and is unlikely to be altered by any new
evidence
Theories vs. Hypotheses
Repeatedly tested
Broader in scope
Take-home message 1.10
 Scientific
theories do not represent
speculation or guesses about the natural
world.
Take-home message 1.10
 Theories
are hypotheses that have been
so strongly and persuasively supported by
empirical observation that the scientific
community views them as very unlikely to
be altered by new evidence.
Well-designed
experiments
are essential to
testing
hypotheses.
1.11 Controlling variables makes
experiments more powerful.
Elements Common
to Most Experiments
1. Treatment
• any experimental condition applied to individuals.
Elements Common
to Most Experiments
2. Experimental group
• a group of individuals who are exposed to a
particular treatment
Elements Common
to Most Experiments
3. Control group
• a group of individuals who are treated identically
to the experimental group with the one exception:
they are not exposed to the treatment
Elements Common
to Most Experiments
4. Variables
• characteristics of your experimental system that
are subject to change
Elements Common
to Most Experiments
1. Treatment
• any experimental condition applied to individuals
2. Experimental group
• a group of individuals who are exposed to a
particular treatment
3. Control group
• a group of individuals who are treated identically
to the experimental group with the one exception:
they are not exposed to the treatment
4. Variables
• characteristics of your experimental system that
are subject to change
Controlling Variables
 the
most important feature of a good
experiment
 the
attempt to minimize any differences
between a control group and an
experimental group other than the
treatment itself
Why does this experiment fall
short of qualifying as a good
example of the scientific method?
 Experimental
 Control
design
group with whom to compare the
treatment group?
Design a more carefully controlled
study.
 160
ulcer patients
 Experimental
 Control
group?
group?
The Placebo Effect
 The
phenomenon in which people respond
favorably to any treatment
 The
placebo effect highlights the need for
comparison of treatment effects with an
appropriate control group.
Clever Hans
Experimental Designs
 Blind
experimental design
• The experimental subjects do not know which
treatment (if any) they are receiving.
 Double-blind
experimental design
• Neither the experimental subjects nor the
experimenter knows which treatment the
subject is receiving.
Hallmarks of an Extremely
Well-designed Experiment
 Blind/double-blind
strategies
 Randomized
• The subjects are randomly assigned into
experimental and control groups.
Take-home message 1.11
• To draw clear conclusions from experiments, it is
essential to hold constant all those variables we
are not interested in.

Control and experimental groups should vary
only with respect to the treatment of interest.

Differences in them can then be attributed to
the treatment.
1·12 THIS IS HOW WE DO IT
Is arthroscopic surgery for
arthritis of the knee
beneficial?
How could you determine
whether a particular type
of surgery is effective?
How does general scientific
literacy—particularly among nonscientists such as the volunteers in
this study—help in advancing our
knowledge and understanding
about a particular phenomenon?
The Treatment Groups
1. Arthroscopic surgery with
debridement
2. Arthroscopic surgery with lavage
3. Placebo surgery
How did the researchers decide
whether the arthroscopic
surgery was effective?
What is the take-home
message from these two
graphs?
At two years, the pain
scores were:
Patient Group
Mean Pain Score
1. Debridement
51 ± 23
2. Lavage
54 ± 24
3. Placebo
52 ± 24
What conclusions can you draw from
these results?
Take-home message 1.12
• In a well-controlled experiment, researchers
demonstrated that arthroscopic knee surgery
for osteoarthritis was no more beneficial for
patients—in terms of knee pain and knee
functioning—than a placebo surgery.
1.13 Repeatable experiments
increase our confidence.
Can science be misleading?
How can we know?
Do megadoses of
vitamin C reduce
cancer risk?
An experiment must be
reproducible and repeatable.
Take-home message 1.13
 Experiments
and their outcomes must be
repeatable for their conclusions to be valid
and widely accepted.
1.14 We’ve got to watch
out for biases.
Can scientists be sexist?
How would we know?
Take-home message 1.14
 Biases
can influence our behavior,
including our collection and interpretation
of data.
 With
careful controls, it is possible to
minimize such biases.
Scientific
thinking can
help us make
wise
decisions.
1.15 Visual displays of data can
help us understand and explain
phenomena.
Variables
• Independent Variables
– some measurable entity that is available at
the start of a process and whose value can be
changed as required.
• Dependent Variables
– created by the process being observed and
whose value cannot be controlled.
Take-home message 1.15
• Visual displays of data, which condense
large amounts of information, can aid in
the presentation and exploration of the
data.
Take-home message 1.15
• The effectiveness of such displays is
influenced by the precision and
clarity of the presentation, and it can
be reduced by ambiguity, biases,
hidden assumptions, and other issues
that reduce a viewer’s confidence in
the underlying truth of the presented
phenomenon.
1.16 Statistics can help us
in making decisions
Statistics
A set of analytical and mathematical tools
designed to help researchers gain
understanding from the data they gather.
• Drawing
conclusions based
on limited
observations is
risky.
• Measuring a greater
number of people will
generally help us draw
more accurate
conclusions about
human height.
Making Wise Decisions
About Concrete Things
 Does
having access to a textbook help a
student to perform better in a biology
class?
• Students who had access to a textbook scored
an average of 81% ± 8% on their exams…
• …while those who did not scored an average
of 76% ± 7%.
Statistics can also help us to identify
relationships (or the lack of
relationships) between variables.
a
positive correlation
• meaning that when one variable increases, so
does the other
 “Correlation
 Statistical
is not causation.”
analyses can help us to organize
and summarize.
Take-home message 1.16
 Because
much variation exists in the
world, statistics can help us evaluate
whether differences between a treatment
and control group can be attributed to the
treatment rather than random chance.
1.17 Pseudoscience and misleading
anecdotal evidence can obscure the
truth.
How to Prevent Being Taken in or
Fooled by False Claims
 Identify
two types of “scientific evidence”
that frequently are cited in the popular
media and are responsible for people
erroneously believing that links between
two things exist, when in fact they do not.
1. Pseudoscience: individuals make
scientific-sounding claims that are not
supported by trustworthy, methodical
scientific studies.
2. Anecdotal observations: based on only
one or a few observations, people
conclude that there is (or is not) a link
between two things.
“Four out of five dentists surveyed
recommend sugarless gum for their
patients who chew gum.”

“How do they know what they know?”

Maybe the statement is factually true, but the
general relationship it implies may not be.
Anecdotal Observations
 do
not include a sufficiently large and
representative set of observations of the
world
 data
are more reliable than anecdotes
Q
Does the measles, mumps,
and rubella vaccine cause
autism?
Science is a way to call the bluff of those
who only pretend to knowledge. It is a
bulwark against mysticism, against
superstition, against religion misapplied to
where it has no business being. If we’re
true to its values, it can tell us when we’re
being lied to.
—Carl Sagan
Take-home message 1.17
 Pseudoscience
and anecdotal observations
often lead people to believe that links
between two phenomena exist, when in
fact there are no such links.
1.18 There are limits to what
science can do.
One of Several Approaches to the
Acquisition of Knowledge

The scientific method is, above all, empirical.

Value judgments and subjective information

Moral statements and ethical problems
Take-home message 1.18
 Although
the scientific method may be the
most effective path toward understanding
the observable world, it cannot give us
insights into the generation of value
judgments and other types of nonquantifiable, subjective information.
On the road to
biological
literacy:
what are the
major themes
in biology?
• 1.19 Important unifying
themes tie together the diverse
topics in biology.
What is Life?
Try to define it
Characteristics shared by all living
organisms and living systems:
• A complex, ordered organization
consisting of one or more cells.
• The use and transformation of energy
to perform work.
• Sensitivity and responsiveness to the
external environment.
Characteristics shared by all living
organisms and living systems:
• Regulation and homeostasis.
• Growth, development, and
reproduction.
• Evolutionary adaptation leading to
descent with modification over time.
Two Unifying Themes
 Hierarchical
 The
organization
power of evolution
4 Chief Areas of Focus
1. The chemical, cellular, and energetic
foundations of life
2. The genetics, evolution, and behavior of
individuals
3. The staggering diversity of life and the unity
underlying it
4. Ecology, the environment, and the subtle
and important links between organisms and
the world they inhabit
Take-home message 1.19
• “Life” is not easily described with a simple
definition.
Take-home message 1.19
• The characteristics shared by all
living organisms include:
– complex and ordered organization;
– the use and transformation of energy;
– responsiveness to the external environment.
Take-home message 1.19
• The characteristics shared by all
living organisms include:
– regulation and homeostasis;
– growth, development, and reproduction;
– and evolutionary adaptation leading to
descent with modification.
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