Chapter 1: Scientific Thinking

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Chapter 1 Scientific Thinking

• Your best pathway to understanding the world

Lectures by Mark Manteuffel, St. Louis Community
College
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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.

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1.1 What is science? What is biology?
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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?

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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.

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How do you know that is true?

• The single question that underlies scientific
  thinking

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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?

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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?

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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

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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.

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1.2 Biological literacy is essential in the
modern world.

• A brief glance at any newspaper will reveal

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• 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?

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Biological Literacy

• The ability to
• use the process of scientific inquiry to think
  creatively about real-world issues,
• communicate those thoughts to others, and
• integrate them into your decision-making.

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• Scientific issues permeate the law. I believe
  that in this age of science we must build legal
  foundations that are sound in science as well as
  in law. The result, in my view, will further not
  only the interests of truth but also those of
  justice.
• U.S. Supreme Court Justice Stephen Breyer
• February, 1998 at the annual meeting of the
• American Association for the Advancement of
  Science

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Take-home message 1.2

• Biological issues permeate all aspects of our
  lives.
• To make wise decisions, it is essential for
  individuals and societies to attain biological
  literacy.

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1.3 The scientific method is a powerful approach
to understanding the world.

• If science proves some belief of Buddhism wrong,
  then Buddhism will have to change
• Dalai Lama, 2005

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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.

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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

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Scientific Thinking Is Empirical

• based on experience and observations that are
  rational, testable, and repeatable.

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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.

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• 1.4 Thinking like a scientist how to use the
  scientific method

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Scientific Method

• A rigid process to follow?
• A recipe?
• An adaptable process?
• One that includes many different methods?

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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.

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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.

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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 chemical runoff give rise to hermaphrodite
  fish?
• Does shaving hair from your face, legs, or
  anywhere else cause it to grow back coarser or
  darker?

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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.

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1.5 Step 1 Make observations.

• Look for interesting patterns or cause-and-effect
  relationships.

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Does taking echinacea reduce the intensity or
duration of the common cold?
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Take-home message 1.5

• The scientific method begins by making
  observations about the world, noting apparent
  patterns or cause-and-effect relationships.

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1.6 Step 2 Formulate a hypothesis.

• A proposed explanation for
• observed phenomena

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To be most useful, a hypothesis must accomplish
two things

• It must clearly establish mutually exclusive
  alternative explanations for a phenomenon.
• It must generate testable predictions.

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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.

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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.

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Take-home message 1.6

• A hypothesis is a proposed explanation for a
  phenomenon.

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Step 3 Devise a testable prediction.

• Suggest that under certain conditions we will
  make certain observations.

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Devising a Testable Prediction from a Hypothesis

• Keep in mind any one of several possible
  explanations could be true.

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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.

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Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
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Take-home message 1.7

• For a hypothesis to be useful, it must generate a
  testable prediction.

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1.8 Step 4 Conduct a critical experiment.

• an experiment that makes it possible to
  decisively determine whether a particular
  hypothesis is correct

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Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
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Take-home message 1.8

• A critical experiment is one that makes it
  possible to decisively determine whether a
  particular hypothesis is correct.

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1.9 Step 5 Draw conclusions, make revisions.

• Trial and error

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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.

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Making Revisions

• Try to further refine a hypothesis.
• Make new and more specific testable predictions.

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Does echinacea help prevent the common cold?
Hypothesis Echinacea reduces the duration and
severity of the symptoms of the common cold.
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Take-home message 1.9

• Experimental test results can be used to revise
  hypotheses and explain the observable world more
  accurately.
• Scientific thinking helps us to understand when
  we should change our minds.

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1.10 When do hypotheses become theories?

• Two distinct levels of understanding that
  scientists use in describing our knowledge about
  natural phenomena

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Hypotheses and Theories

• A hypothesis is a proposed explanation for a
  phenomenon.
• a good hypothesis leads to testable predictions.

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Hypotheses and Theories

• A theory is a hypothesis for natural phenomena
  that is exceptionally well-supported by the data.
• a hypothesis that has withstood the test of time
  and is unlikely to be altered by any new evidence

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Theories vs. Hypotheses

• Repeatedly tested
• Broader in scope

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Take-home message 1.10

• Scientific theories do not represent speculation
  or guesses about the natural world.

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Take-home message 1.10

• Theories are hypotheses that have been so
  strongly supported by empirical observation that
  the scientific community views them as very
  unlikely to be altered by new evidence.

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• 1.11 Controlling variables makes experiments
  more powerful.

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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

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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

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Why does this experiment fall short of qualifying
as a good example of the scientific method?

• Experimental design
• Control group with whom to compare the treatment
  group?

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Design a more carefully controlled study.

• 160 ulcer patients
• Experimental group?
• Control group?

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Is arthroscopic surgery for arthritis beneficial
for the 300,000 people who have it each year?

• How do we know?

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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.

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Take-home message 1.11

• In 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.

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1.12 Repeatable experiments increase our
confidence.

• Can science be misleading?
• How can we know?

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Do megadoses of vitamin C reduce cancer risk?

• An experiment must be reproducible and repeatable.

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Take-home message 1.12

• Experiments and their outcomes must be repeatable
  for their conclusions to be valid and widely
  accepted.

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1.13 Weve got to watch out for biases.

• Can scientists be sexist?
• How would we know?

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Take-home message 1.13

• Biases can influence our behavior, including our
  collection and interpretation of data.
• With careful controls, it is possible to minimize
  such biases.

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1.15 Pseudoscience and misleading anecdotal
evidence can obscure the truth.
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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.

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• Pseudoscience individuals make
  scientific-sounding claims that are not supported
  by trustworthy, methodical scientific studies.
• Anecdotal observations based on only one or a
  few observations, people conclude that there is
  or is not a link between two things.

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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.

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Anecdotal Observations

• do not include a sufficiently large and
  representative set of observations of the world
• data are more reliable than anecdotes

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• 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 were true to its values, it can tell
  us when were being lied to.
• Carl Sagan

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Take-home message 1.15

• Pseudoscience and anecdotal observations often
  lead people to believe that links between two
  phenomena exist, when in fact there are no such
  links.

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1.16 There are limits to what science can do.

• The scientific method will never prove or
  disprove the existence of God.
• Understand elegance?
• What is beauty?

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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

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Take-home message 1.16

• 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 non-quantifiable, subjective information.

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• 1.17 A few important themes tie together the
  diverse topics in biology.

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Two Unifying Themes

• Hierarchical organization
• The power of evolution

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Take-home message 1.17

• Although the diversity of life on earth is
  tremendous, the study of life is unified by the
  themes of hierarchical organization and the power
  of evolution.