biol 108 - chp 1: scientific thinking

Scientific ThinkingScientific Thinking

BIOL BIOL 108 Intro to Bio 108 Intro to Bio SciSci

Chapter 1Chapter 1

Rob Rob SwatskiSwatski Assoc Prof BiologyAssoc Prof Biology HACCHACC--YorkYork

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Learning GoalsLearning Goals Learning GoalsLearning Goals

Describe what science

is.

Describe the scientific method.

Describe the 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 1.1

What What is science? is science?

What What is biology? is biology?

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ScientistsScientists ScientistsScientists

Are curious

Ask questions about how the

world works

Seek answers

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Science is NOT simply a body ofScience is NOT simply a body of knowledge or a list of facts to knowledge or a list of facts to

bebe remembered…remembered… 6

Science is an intellectual activity, Science is an intellectual activity, encompassing observation, description, encompassing observation, description, experimentation, and explanation of experimentation, and explanation of natural phenomena.natural phenomena.

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“How do you know that is true?” “How do you know that is true?”

The single question that underlies scientific thinking 8

Can we trust the packaging claims that Can we trust the packaging claims that companies make?companies make?

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Don’t be at the mercy of cranks, Don’t be at the mercy of cranks, charlatans, advertising, or slick charlatans, advertising, or slick

packagingpackaging

Learn exactly what it means to have

scientific proof or evidence

Learn what it means to think scientifically

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The most The most important important

questions in questions in biology:biology:

The most The most important important

questions in questions in biology:biology:

What is the chemical and physical basis for life and

its maintenance?

What is the chemical and physical basis for life and

its maintenance?

How do organisms use genetic information to

build themselves and to reproduce?

How do organisms use genetic information to

build themselves and to reproduce?

What are the diverse forms that life on Earth takes and how has that

diversity arisen?

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?

How do organisms interact with each other and with

their environment? 11

How to think scientifically

Increasingly important in our

lives

How to use the knowledge we

gain to make wise decisions

Literacy in matters of biology is

especially essential

Scientific LiteracyScientific Literacy

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TakeTake--Home Message 1.1Home 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.

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. 13

1.2 Biological literacy is essential in the modern world.

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Biological LiteracyBiological Literacy Biological LiteracyBiological Literacy

Use the process of scientific inquiry to

think creatively

about real-world issues

Communicate those

thoughts to others

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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Biological issues permeate all aspects of

our lives.

To make wise decisions, it is essential for

individuals and societies to attain biological

literacy. 17

The Culture of Science: The Culture of Science: CreativityCreativity 18

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

Why and when Why and when do people do people develop develop superstitions & superstitions & belief in the belief in the paranormal? paranormal?

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The Scientific The Scientific MethodMethod

The Scientific The Scientific MethodMethod

An empirical process of examination &

discovery

Based on experience & observations that

are rational, testable, & repeatable

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The Scientific MethodThe Scientific Method

Observe a phenomenon

Propose an explanation for it

Test the proposed explanation through a series of experiments

Explanation is accurate & valid

Revise or propose alternative

explanations 23


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. 24

1.4 Thinking like a scientist: 1.4 Thinking like a scientist: how to use the scientific how to use the scientific

methodmethod 26

What is the Scientific What is the Scientific Method?Method?

What is the Scientific What is the Scientific Method?Method?

A rigid process

to follow? A recipe?

An adaptable process?

One that includes

many different

methods?

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1. Make Observations

2. Formulate a hypothesis

3. Devise a testable prediction

4. Conduct a critical experiment

5. Draw conclusions and make revisions 28

What should you do when What should you do when something you believe in turns something you believe in turns

out to be wrong?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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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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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 1.5 Step 1Step 1: Make observations.: Make observations.

Look for interesting patterns or cause-and-

effect relationships.

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Does taking Does taking echinaceaechinacea reduce the intensity or reduce the intensity or duration of the common cold?duration of the common cold?

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The scientific method begins by making

observations about the world, noting apparent

patterns or cause-and-effect relationships.

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1.6 1.6 Step 2Step 2: Formulate a hypothesis.: Formulate a hypothesis.

A proposed explanation for

observed phenomena

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To be most useful, a hypothesis To be most useful, a hypothesis must accomplish two things:must accomplish two things:

It must clearly establish mutually exclusive

alternative explanations for a phenomenon

It must generate testable predictions

The Null HypothesisThe Null Hypothesis The Null HypothesisThe 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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HypothesisHypothesis HypothesisHypothesis

Echinacea reduces the duration and severity of the symptoms of the common cold.

Null Null HypothesisHypothesis

Null Null HypothesisHypothesis

Echinacea has no effect on the duration

or severity of the symptoms of the

common cold.


A hypothesis is a proposed explanation

for a phenomenon.

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1.7 1.7 Step 3Step 3: Devise a testable : Devise a testable prediction.prediction.

Suggest that under certain conditions we

will make certain observations.

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PredictionsPredictions PredictionsPredictions

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.

Keep in mind any one of several possible

explanations could be true.

Hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold.

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Hypothesis: Eyewitness testimony is always accurate.

Prediction: If individuals have witnessed a crime, then they

will correctly identify the criminal regardless of whether

multiple suspects are presented in a lineup one at a time or all at

the same time.

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Hypothesis: Estrogens in sewage runoff turn fish into

hermaphrodites.

Prediction: If estrogens in sewage runoff turn fish into

hermaphrodites, then exposing fish to estrogens should cause

them to turn into hermaphrodites more frequently than fish not

exposed to estrogens.

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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.


For a hypothesis to be useful, it must generate

a testable prediction.

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1.8 1.8 Step 4Step 4: Conduct a critical : Conduct a critical experiment.experiment.

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

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Estrogens in sewage runoff turn fish into

hermaphrodites.

Critical experiment

ideas?

57


Hair that is shaved grows

back coarser and darker.

Critical experiment

ideas?


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 1.9 Step 5: Draw conclusions, make revisions.revisions.

Trial and error

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The Role of ExperimentsThe Role of Experiments The Role of ExperimentsThe Role of Experiments

It is important 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.

60

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Making Making RevisionsRevisions Making Making

RevisionsRevisions

Try to further refine a

hypothesis

Make new and more specific

testable predictions


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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 1.10 When do hypotheses become theories?become theories?

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Two distinct levels of understanding that

scientists use in describing our knowledge about natural phenomena

65


A proposed explanation for a

phenomenon

A good hypothesis leads

to testable predictions

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TheoryTheory TheoryTheory

A hypothesis for natural phenomena that is exceptionally well-

supported by the data.

A hypothesis that has withstood the test of

time & has been repeatedly tested

Is unlikely to be altered by any new evidence


Scientific theories do not represent speculation or guesses

about the natural world.

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 1.11 Controlling variables makes experiments more powerful.experiments more powerful.

69

Elements Common to Most Elements Common to Most ExperimentsExperiments

Elements Common to Most Elements Common to Most ExperimentsExperiments

1. Treatment 2.

Experimental group

3. Control group

4. Variables

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1. Treatment1. Treatment Any experimental condition applied to

individuals

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2. Experimental group2. Experimental group A group of individuals who are

exposed to a particular treatment

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3. Control group3. Control group A group of individuals who are

treated identically to the experimental

group with one exception: they are not exposed to the

treatment

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4. Variables4. Variables Characteristics of your experimental

system that are subject to change

75

Controlling Controlling VariablesVariables

Controlling Controlling VariablesVariables

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

77

The Placebo The Placebo EffectEffect

The Placebo The Placebo EffectEffect

The phenomenon in which people respond

favorably to any treatment

Highlights the need for comparison of treatment effects

with an appropriate control group

78

Clever HansClever Hans

Experimental DesignsExperimental Designs

BlindBlind

The experimental subjects do not know which

treatment (if any) they are receiving

DoubleDouble--blindblind

Neither the experimental subjects nor the

experimenter knows which treatment the subject is

receiving 79

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RandomizedRandomized

The subjects are randomly

assigned into experimental and

control groups


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.

81

1.12 Repeatable experiments 1.12 Repeatable experiments increase our confidence.increase our confidence.

Can science be misleading?

How can we know?

82

Do Do megadosesmegadoses of vitamin C of vitamin C reduce cancer risk?reduce cancer risk?

An experiment must be reproducible and repeatable.

85


Experiments and their outcomes must be repeatable for their

conclusions to be valid and widely accepted.

86

1.13 We’ve got to watch out for 1.13 We’ve got to watch out for biases.biases.

Can scientists be sexist?

How would we know?

87


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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1.14-1.17

Scientific thinking

can help us make

wise decisions.

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1.14 1.14 Visual displays of data Visual displays of data can help us understand and can help us understand and

explain phenomena.explain phenomena.

91

VariablesVariables

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.

94

TakeTake--home message 1.14home message 1.14

Visual displays of data, which condense large amounts of information, can aid in the presentation and exploration of the data.

95

1.15 Statistics can help us to make 1.15 Statistics can help us to make decisions.decisions.

96

A set of analytical & 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.

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Making Wise DecisionsMaking Wise Decisions About Concrete ThingsAbout 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%.

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100

StatisticsStatistics StatisticsStatistics Can help us to identify

relationships (or the lack of relationships) between

variables

Positive correlation: when one variable increases, so

does the other

“Correlation is not causation.”

Statistical analyses can help us to organize & summarize


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.

101

1.16 1.16 Pseudoscience and Pseudoscience and

misleading misleading anecdotal anecdotal

evidence can evidence can obscure the truth.obscure the truth.

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103

PseudosciencePseudoscience PseudosciencePseudoscience

Individuals make scientific-sounding claims that are not supported by trustworthy, methodical

scientific studies

Anecdotal Anecdotal observationsobservations


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 “Four out of five dentists surveyed recommend sugarless gum for their patients recommend sugarless gum for their patients

who chew gum.”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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Do not include a sufficiently large and representative set of observations of the

world

Data are more reliable than anecdotes

“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

106


Pseudoscience and anecdotal observations

often lead people to believe that links between two

phenomena exist, when in fact there are no such links.

107

1.17 There are limits to what 1.17 There are limits to what science can do.science can do.

1.17 There are limits to what 1.17 There are limits to what science can do.science can do.

The scientific method will never prove or disprove

the existence of

God.

Understand elegance?

What is beauty?

108

109

Approaches to the Acquisition Approaches to the Acquisition of Knowledgeof Knowledge

The scientific method is, above

all, empirical

Value judgments and subjective

information

Moral statements and

ethical problems


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.

110

1.18

On the road to

biological

literacy: what are

the major themes

in biology?

111

1.18 A few important themes tie 1.18 A few important themes tie together the diverse topics in biology.together the diverse topics in biology.

112

Hierarchical organization

The power of evolution

Four Chief Areas of FocusFour 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

113


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.

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biol 108 - chp 1: scientific thinking

Education

scientific method observation

scientific thinkingbiol

scientific methodtest

scientific issues

scientific method26

home message

scientific proof orto

age of science