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Chapter 1: Section 2
How Scientists Work
Notes
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Much of biology deals with solvingproblems
These problems can be environmental,ecological, health related, etc.
No matter what types of problemsare being studied, scientists usethe same problem-solving stepscalled
The Scientific Method
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Make an Observation
Define the Problem
Research the Problem
State the Hypothesis
Experiment to test Hypothesis
Collect and Record Data
Analyze Data
Draw Conclusions
Determine Limitations
Report ResultsIf needed, Do more investigation
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Then
And
Question
Research
Hypothesis
Procedure/Method
Data
Observations
Conclusion
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
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Then
And
Question
Research
Hypothesis
Procedure/Method
Data
Observations
Conclusion
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
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Repeat steps 3-7 for competing hypotheses.
Competing hypotheses may include revisionsof the original hypothesis suggested by the
results of the testing process.
Hypothesis
F
indings
(Co
nclusions)
Data(Results)
Procedures
(E
xperimen
ts)
ScientificMethod
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Here is anotherexample of how the
steps may go.
Even though weshow the scientific
method as a series
of steps, keep inmind that newinformation or
thinking might
cause a scientist toback up and repeatsteps at any pointduring the process.
Form aHypothesis
Make
Observations
Define / Identifythe Problem
Test HypothesisPerform Experiments
NewExperiments
Do Experimentsand Observations
Support Hypothesis?
YES
Organize andAnalyze Data
Draw ValidConclusions
NO
CommunicateResults
FaultyExperiments?
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Lets break
each of thesesteps down
into theirindividualcomponents:
Ask Question
Do BackgroundResearch
ConstructHypothesis
Test with anExperiment
Analyze Results
Draw Conclusion
Think!Try Again
Report Results
Hypothesis is TrueHypothesis is False
or Partially True
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Make anobservation
Seesomethingunusual
Frogs with
incorrectnumber oflegs!
As we all know, frogs have four legs.
Whats up
with thesefroggies?
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Recognize, state or define theproblem
Must be in the form of a question
The obvious question is: What is causing these deformities?
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Gather information related to the problem Read, observe, measure, take samples, etc. How frogs normally develop from eggs
The % of frogs with thedeformities
Number of other species inthe pond with deformities
Previous or new pollutantsin the pond
Change in amount of UV(sunlight) exposure on eggs
Etc.
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A hypothesis is:
An educated guess, trial answer, possible
solution, prediction Must be a statement
Must be testable or measurable
Is based on your researchand previous experience
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Some possible explanations (hypotheses)for the frog deformities:Genetic mutation
Chemical PollutionUltraviolet Radiation
Disease (virus or parasite or...?)
Loud Rock & Roll MusicAliens from outer space
Something else
Genetic mutation-
If this hypothesis is true, then:
If we mate deformed frogs the offspringshould show similar deformitiesThe deformities should be fairly uniform
and predictableThe particular deformities should only befound in one species
Chemical Pollution-If this hypothesis is true, then:
You should be able to find a likely chemical pollutant in
the deformed frog pondsYou should be able to isolate the chemical from the pondwaterYou should be able to show that the isolated chemical cancause the exact same deformities in the lab
These are minimal predictions; you may have alreadythought of the fact that chemical pollution should affectall four limbs equally, or that other organisms from thesame ponds should show deformities as well
Ultraviolet Radiation-
If this hypothesis is true, then:
We should be able to measure unusually highlevels of UV radiation at deformed frog sitesWe should be able to use these same levels toinduce the exact same kinds of deformities in thelabCan you think of other predictions based on thishypothesis?
Disease (virus, parasite, etc.)-If this hypothesis is true, then:
We should be able to find the disease-causing
agent (for example, parasites) at the deformedfrog pondsWe should be able to find the parasites in thedeformed frogs
We should be able to use the same parasite toinduce the exact same kinds of deformities in thelab
Loud Rock + Roll Music-
Okay, this is testable,but WHY test it???
(get real)
Aliens from outer space-
Sorry,this is not allowed becauseit is not testable using the
Scientific Method.Sheesh!
Something Else-
Another possibility that we might think ofis predation or cannibalism, which seemsto be the best explanation for certain kindsof deformities (frogs with missing limbs).If this hypothesis is true, then, at minimum:
We should find frogs and/or other pondcritters with evidence that their legs havebeen damaged or bitten off
http://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/mutants.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/mutants.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/mutants.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/mutants.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/mutants.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/predation.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/sorry.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/why.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/parasites.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/UV.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/chemicals.htmlhttp://info.hartwick.edu/biology/def_frogs/Introduction/Exploration/mutants.html -
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Testing the hypothesis
Pick the hypothesis that makes the most
sense and iseasy to test
Then design a
controlledexperiment
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Go to the web site for Hartwick College tosee the experiments and how
the scientific method wasactually used to find out thecause of recently foundfrog deformities.
http://www.hartwick.edu/biology/def_frogs/Introduction/Exploration/explore.html
http://www.hartwick.edu/biology/def_frogs/Introduction/Exploration/explore.htmlhttp://www.hartwick.edu/biology/def_frogs/Introduction/Exploration/explore.htmlhttp://www.hartwick.edu/biology/def_frogs/Introduction/Exploration/explore.htmlhttp://www.hartwick.edu/biology/def_frogs/Introduction/Exploration/explore.htmlhttp://www.hartwick.edu/biology/def_frogs/Introduction/Exploration/explore.html -
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Lets look at the text book example of
the Scientific Method using Redis Experiment
on Spontaneous Generation
He was trying to disprovethe idea of SpontaneousGeneration (or actually
that flies came frommaggots, which camefrom flies)
Francesco Redi (1668)
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Example: How do new livingthings come into being?
Spontaneous generation once
commonly accepted Redi wanted to show what
caused the appearance ofmaggots (and then flies) on meat
http://www.bayerhome.co.za/media/SchoolProjects/flyOnMeat.jpghttp://images.google.com/imgres?imgurl=http://hh.cocolog-nifty.com/blog/images/frog-2l_2.jpg&imgrefurl=http://www.worth1000.com/cache/contest/contestcache.asp%3Fcontest_id%3D9468&h=820&w=800&sz=80&hl=en&start=46&um=1&tbnid=TR8BjF9_2dHJPM:&tbnh=144&tbnw=140&prev=/images%3Fq%3Dfrog%26start%3D40%26ndsp%3D20%26svnum%3D10%26um%3D1%26hl%3Den%26sa%3DN -
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If leaf lands on water it becomes a fish
If bale of hay left in barn it produces mice
Muddy soil gives rise to frogs
Meat hung out in the market is the sourceof flies
http://www.bayerhome.co.za/media/SchoolProjects/flyOnMeat.jpghttp://images.google.com/imgres?imgurl=http://hh.cocolog-nifty.com/blog/images/frog-2l_2.jpg&imgrefurl=http://www.worth1000.com/cache/contest/contestcache.asp%3Fcontest_id%3D9468&h=820&w=800&sz=80&hl=en&start=46&um=1&tbnid=TR8BjF9_2dHJPM:&tbnh=144&tbnw=140&prev=/images%3Fq%3Dfrog%26start%3D40%26ndsp%3D20%26svnum%3D10%26um%3D1%26hl%3Den%26sa%3DN -
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Forming a Hypothesis
Redis Hypothesis:Flies produce maggots.
How could he test this? Through a controlled experiment
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Redi used two groups of jars
Jars that contained meat and no cover
Jars that contained meat and gauze cover
Jars with meat
Uncovered jars
Covered jars
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used as a standard ofcomparison
the group containingthe factor (variable) that has been changed
Uncovered jars
Covered jars
Two groups
of jars
Control group:
Experimental group:
(manipulated or independent variable)
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Variables - Factors that can be changed Controlled Variables - all the variables that
remain constant
Manipulated Variable - (also called theIndependent Variable) - factor in an experimentthat a scientist purposely changes
Responding Variable- (also called the
Dependent Variable) - the outcome or results,factor in an experiment that may change becauseof the manipulated variable.what a scientist wants to observe
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In a controlled experiment,only one factor is changed at atime.
Independent variable:the factor that is deliberatelychanged
Dependent variable:
the factor that the scientistwants to observe; it changesin response to the
independent variable
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1. Which is the control group?
2. Which is the experimental group?
Two groups ofJars with meat
Uncovered jars
Covered jars
Covered jars
Uncovered jars
Redis Experiment on Spontaneous Generation
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OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.HYPOTHESIS: Flies produce maggots.PROCEDURE
Manipulated Variables:gauze covering thatkeeps flies away frommeat
Uncoveredjars Covered jars
Severaldays pass
Maggots appear No maggots appearResponding Variable:whether maggotsappear
CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous
generation of maggots did not occur.
Controlled Variables:jars, type of meat,location, temperature,time
Redi s Experiment on Spontaneous Generation
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Examine data tables,charts, and graphs
Examine experimentalnotes
Look for trends, patterns,and averages
What does the data show
Put your data into words
http://images.google.com/imgres?imgurl=http://www.ozintell.com/images/CO2_GAS_EXPERIMENT.JPG&imgrefurl=http://www.ozintell.com/multilogpro.htm&h=429&w=425&sz=35&hl=en&start=6&tbnid=qenXnqbX7RM2sM:&tbnh=126&tbnw=125&prev=/images%3Fq%3Dscience%2Bexperiment%2Banalyze%26gbv%3D2%26svnum%3D10%26hl%3Den -
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Restate the hypothesis:
Example: Flies produce maggots.
Accept or reject the hypothesis. Support your conclusion with specific, numerical data.
What was Redis conclusion? Flies lay eggs too small to be seen. Maggots found on rotting meat are produced
from the eggs laid by flies. Maggots are not appearing due to
spontaneousgeneration!
http://images.google.com/imgres?imgurl=http://images.inmagine.com/168nwm/itstock/itf139/itf139053.jpg&imgrefurl=http://www.inmagine.com/bugs-photos/itstock-itf139&h=168&w=168&sz=11&hl=en&start=3&tbnid=8YLylIqC3ztVrM:&tbnh=99&tbnw=99&prev=/images%3Fq%3Dmaggots%2Bon%2Bmeat%26gbv%3D2%26svnum%3D10%26hl%3Denhttp://images.google.com/imgres?imgurl=http://bugs.bio.usyd.edu.au/Entomology/images/Topics/importance/flies.jpg&imgrefurl=http://bugs.bio.usyd.edu.au/Entomology/importance/imagePages/flies.html&h=300&w=428&sz=25&hl=en&start=2&tbnid=roiUonj5-h27zM:&tbnh=88&tbnw=126&prev=/images%3Fq%3Dflies%2Bon%2Bmeat%26gbv%3D2%26svnum%3D10%26hl%3Den -
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Scientists look for possibleflaws in their research
They look for faulty
(inaccurate) data They look for experimental
error or bias's
They decide on the validityof their results
They make suggestions for improvement orraise new questions
http://images.google.com/imgres?imgurl=http://marksarvas.blogs.com/elegvar/images/scream.bmp&imgrefurl=http://marksarvas.blogs.com/elegvar/2004/08/index.html&h=1052&w=813&sz=2507&hl=en&start=78&um=1&tbnid=lNM8-u3tz0qLjM:&tbnh=150&tbnw=116&prev=/images%3Fq%3Dflawed%2Bexperiment%2Bjokes%26start%3D60%26ndsp%3D20%26svnum%3D10%26um%3D1%26hl%3Den%26rls%3DGGLB,GGLB:1969-53,GGLB:en%26sa%3DN -
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Communication is anessential part of science
Scientists report their
results in journals,on the internet, orat conferences
This allows their
experiments to beevaluated and repeated
Scientists can build on previouswork of other scientistsRedis experiment
on insects generation
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Sometimes results are unexpected.
John Needham challenged Redis experimentand designed his own to show thatspontaneous generation CAN occur undercertain circumstances.
Lazzaro Spallanzinidesigned a slightlydifferent experimentto improve onNeedhams work
Repeat the experiment!
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Louis Pasteur further modified theexperiment.
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State the
Hypothesis
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Make an
Observation the Problem
Determine
Limitations
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Define the
Problem
1
Analyze Data
2
Report Results
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A theory is anexplanation of a set ofrelated observations
or events based uponproven hypothesesand verified multipletimes by detached
groups of researchers
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