Scientific MethodScientific Method

How Scientists WorkHow Scientists Work

NotesNotes

How Scientists Work:How Scientists Work: Solving the ProblemsSolving the Problems

Much of biology deals with solving Much of biology deals with solving problemsproblems

These problems can be environmental, These problems can be environmental, ecological, health related, etc.ecological, health related, etc.

No matter what types of problemsNo matter what types of problemsare being studied, scientists use are being studied, scientists use the same problem-solving steps the same problem-solving steps called…called…

The Scientific MethodThe Scientific Method

Then

And

QuestionQuestion

ResearchResearch

HypothesisHypothesis

Procedure/Method

Procedure/Method

DataData

ObservationsObservations

ConclusionConclusion

What does the scientist wantto learn more about?

Gathering of information

An “Educated” guess of ananswer to the question

Written and carefullyfollowed step-by-step

experiment designed to testthe hypothesis

Information collected duringthe experiment

Written description of whatwas noticed during the

experiment

Was the hypothesis correct or incorrect?

Next

Then

Next

And

Finally

First

Scientific MethodAn Overview

Scientific MethodScientific Method Let’s break Let’s break

each of each of these steps these steps down into down into their their individual individual components:components:

Ask Question

Do BackgroundResearch

ConstructHypothesis

Test with anExperiment

Analyze ResultsDraw Conclusion

Think!Try Again

Report Results

Hypothesis is True Hypothesis is Falseor Partially True

1. Observing1. Observing

Make an Make an observationobservation See See

somethingsomethingunusualunusual

Frogs withFrogs withincorrectincorrectnumber ofnumber oflegs!legs!

As we all know, frogs have four legs.

What’s up with thesefroggies?

2. Questioning2. Questioning Recognize, state or define the Recognize, state or define the

problemproblem Must be in the form of a question Must be in the form of a question The obvious question is:  The obvious question is: 

What is causing these deformities? What is causing these deformities?

3. Researching3. Researching

Gather information related to the problemGather information related to the problem Read, observe, measure, take samples, etc.Read, observe, measure, take samples, etc. How frogs normally develop from eggsHow frogs normally develop from eggs The % of frogs with the The % of frogs with the

deformitiesdeformities Number of other species in Number of other species in

the pond with deformitiesthe pond with deformities Previous or new pollutantsPrevious or new pollutants

in the pondin the pond Change in amount of UV Change in amount of UV

(sunlight) exposure on eggs (sunlight) exposure on eggs Etc.Etc.

4. Hypothesizing 4. Hypothesizing

A hypothesis is:A hypothesis is: An educated guess, trial answer, possible An educated guess, trial answer, possible

solution, predictionsolution, prediction Must be a statementMust be a statement Must be testable or measurableMust be testable or measurable Is based on your research Is based on your research

and previous experienceand previous experience

Hypothesizing Hypothesizing

List possible explanations List possible explanations (alternative (alternative hypotheses) based on your previous hypotheses) based on your previous experience (what you already know);  experience (what you already know);  and on research you have done   and on research you have done  

all of the hypotheses must be testable all of the hypotheses must be testable (no demons allowed!) (no demons allowed!)

Hypothesizing Hypothesizing Some possible explanations (hypotheses) Some possible explanations (hypotheses)

for the frog deformities: for the frog deformities: Genetic mutation

Chemical Pollution Ultraviolet Radiation Disease (virus or parasite or...?) Loud Rock & Roll Music Aliens from outer space Something else Something else

Hypotheses' usually come in the form of Hypotheses' usually come in the form of “If …. then …..” statements“If …. then …..” statements

Ex: Ex: Question: “How does the size of a wheel Question: “How does the size of a wheel

affect the speed of a HotWheels car?”affect the speed of a HotWheels car?” Hypothesis: “If the car has large wheels, Hypothesis: “If the car has large wheels,

then its speed will be slower.”then its speed will be slower.”

5. Experimenting5. Experimenting

Testing the hypothesisTesting the hypothesis Pick the hypothesis that makes the most Pick the hypothesis that makes the most

sense and is sense and is easy to testeasy to test

Then design a Then design a controlled controlled experimentexperiment

ExperimentingExperimenting

This is a real experiment that was carried This is a real experiment that was carried out using the scientific method.out using the scientific method.

Control and Experimental Control and Experimental GroupsGroups

used as a standard of used as a standard of comparison comparison

the group containing the group containing the factor (variable) that has been changedthe factor (variable) that has been changed

Control groupControl group::

Experimental groupExperimental group::

(manipulated or independent variable)(manipulated or independent variable)

Variables in an Variables in an ExperimentExperiment VariablesVariables - - Factors that can be changedFactors that can be changed Controlled VariablesControlled Variables - - all the variables that remain all the variables that remain

constant constant Independent VariableIndependent Variable (manipulated variable) (manipulated variable) - -

factor in an experiment that a scientist purposely changesfactor in an experiment that a scientist purposely changes Dependent Variable Dependent Variable (aka Responding Variable) (aka Responding Variable) - -

the outcome or results, the factor in an experiment that the outcome or results, the factor in an experiment that may change because of the manipulated variable….may change because of the manipulated variable….what a scientist wants to observewhat a scientist wants to observe

Setting up a Controlled Setting up a Controlled ExperimentExperiment

In a In a controlled experimentcontrolled experiment, , only only one factor is changed at a time.one factor is changed at a time. Independent variableIndependent variable: : the the

factor that is deliberately changedfactor that is deliberately changed Dependent variableDependent variable: : the factor that the scientist wants to the factor that the scientist wants to

observe; it changes in response to observe; it changes in response to the independent variablethe independent variable

6. Collect and Record Data6. Collect and Record Data

Types of Recorded DataTypes of Recorded Data QuantitativeQuantitative - - observations that observations that

involve measurements/numbers; involve measurements/numbers; i.e. 3 days, 12 maggots, 4 g, 13 sec, i.e. 3 days, 12 maggots, 4 g, 13 sec,

8 liters8 liters

QualitativeQualitative - - observations thatobservations thatdo do notnot involve numbers, are of a involve numbers, are of a descriptive naturedescriptive naturei.e. white maggots covered the i.e. white maggots covered the meat, leaves were all wilting meat, leaves were all wilting

observations and measurementsmade in an experiment

Data:Data:

Data is based on facts, not assumptions!Data is based on facts, not assumptions! FactFact: something that has actual existence; : something that has actual existence;

can be proven to be truecan be proven to be true ““School on a normal day at Cleveland HS School on a normal day at Cleveland HS

starts at 7:57 am.”starts at 7:57 am.”

AssumptionAssumption: a notion taken for granted, : a notion taken for granted, usually based on some factual evidenceusually based on some factual evidence ““At Nobel MS, we got out early every Tuesday At Nobel MS, we got out early every Tuesday

so it’s the same at Cleveland HS.”so it’s the same at Cleveland HS.”

7. Analyze the Data7. Analyze the Data

Examine data tables, charts, Examine data tables, charts, and graphsand graphs

Examine experimental notesExamine experimental notes Look for trends, patterns, and Look for trends, patterns, and

averagesaverages What does the data showWhat does the data show Put your data into wordsPut your data into words

8. Draw Conclusions8. Draw Conclusions Collected data is analyzed and one Collected data is analyzed and one

comes up with a conclusion by comes up with a conclusion by deductiondeduction (deriving of a conclusion (deriving of a conclusion by reasoning)by reasoning)

Support your conclusion with specific, Support your conclusion with specific, numerical data.numerical data.

Accept or reject the hypothesis.Accept or reject the hypothesis.

9. Publishing Results9. Publishing Resultso Results of an experiment are useful only if they Results of an experiment are useful only if they

are made available to other scientists so they are made available to other scientists so they can verify resultscan verify results If no one knows about it, no one can prove or If no one knows about it, no one can prove or

disprove it disprove it Unless another scientist can reproduce the Unless another scientist can reproduce the

experiment with the same results, may become an experiment with the same results, may become an inferenceinference (act of passing statistical sample data (act of passing statistical sample data general conclusion) that may be incorrectgeneral conclusion) that may be incorrect Anti-wrinkle creamsAnti-wrinkle creams Weight loss drugs Weight loss drugs Anti-aging pills Anti-aging pills

Why is Publication Necessary?Why is Publication Necessary? Which European is credited with Which European is credited with

“discovering” North America?“discovering” North America? Christopher ColumbusChristopher Columbus

Which European peoples really Which European peoples really “discovered” North America? “discovered” North America? VikingsVikings

Why did Columbus get the credit?Why did Columbus get the credit? Columbus told everyone who would Columbus told everyone who would

listen, whereas the Vikings kept it secretlisten, whereas the Vikings kept it secret

o A A theorytheory is a hypothesis that is is a hypothesis that is supported by a large (humungous) body supported by a large (humungous) body of scientific evidenceof scientific evidenceonly after evidence is collected, tested only after evidence is collected, tested

by different individuals many times, by different individuals many times, and published can a hypothesis and published can a hypothesis become a theorybecome a theory

10. Forming a Theory10. Forming a Theory

Hypothesis vs. Theory vs. LawHypothesis vs. Theory vs. Law What’s the difference between a hypothesis, What’s the difference between a hypothesis,

a theory, and a scientific law?a theory, and a scientific law? hypothesishypothesis: educated guess that has no : educated guess that has no

proofproof “ “I am the best teacher at Cleveland High I am the best teacher at Cleveland High

School.”School.”

theorytheory: hypothesis that is proven correct: hypothesis that is proven correct “ “Smoking Causes Lung Cancer, Heart Smoking Causes Lung Cancer, Heart

Disease, Emphysema, And May Complicate Disease, Emphysema, And May Complicate Pregnancy.”Pregnancy.”

scientific lawscientific law: true and universal fact: true and universal fact “ “What goes up, must come down.”What goes up, must come down.”