get ready for a & p! the scientific method get ready for a & p! the scientific method
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Get Ready for A & P!Get Ready for A & P!
The Scientific MethodThe Scientific Method
Biology Biology
Scientific study of lifeScientific study of life
Lays the foundation for asking basic Lays the foundation for asking basic questions about life and the natural worldquestions about life and the natural world
Anatomy & Physiology is one branch of Anatomy & Physiology is one branch of biologybiology
Why Study Biology?Why Study Biology?
To learn how organisms are constructed, To learn how organisms are constructed, how they function, where they live, and how they function, where they live, and what they do what they do
To help develop, modify, and refine ideas To help develop, modify, and refine ideas about lifeabout life
How do we study Biology?
Biology is studied using the scientific method
Different than other modes of study because it has specific steps and rules
What is the Scientific Method?What is the Scientific Method?
Observe phenomenonObserve phenomenon
Develop hypotheses Develop hypotheses
Make predictionsMake predictions
Devise test of predictionsDevise test of predictions
Carry out test and analyze resultsCarry out test and analyze results
Publish results so others can repeat Publish results so others can repeat
Inductive LogicInductive Logic
Using observations and facts to arrive at Using observations and facts to arrive at
generalizations or hypotheses - begins the generalizations or hypotheses - begins the
scientific methodscientific method
ObservationObservation: Eagles, swallows, and robins : Eagles, swallows, and robins
have feathershave feathers
HypothesisHypothesis: All birds have feathers: All birds have feathers
Deductive LogicDeductive Logic
Drawing a specific conclusion based on a Drawing a specific conclusion based on a
generalization - after testing a hypothesis generalization - after testing a hypothesis
GeneralizationGeneralization - Birds have feathers - Birds have feathers
ExampleExample - Eagles are birds - Eagles are birds
ConclusionConclusion - Eagles have feathers - Eagles have feathers
Role of ExperimentsRole of Experiments
Used to study a phenomenon under Used to study a phenomenon under known conditions known conditions
Allows you to predict what will happen if a Allows you to predict what will happen if a hypothesis is supportedhypothesis is supported
Can never Can never proveprove a hypothesis 100% a hypothesis 100% correctcorrect
Experimental Design Experimental Design
Control group Control group A standard for comparisonA standard for comparison
Identical to experimental group except for Identical to experimental group except for
variable being studiedvariable being studied
Sampling errorSampling error Nonrepresentative sample skews resultsNonrepresentative sample skews results
Minimize by using large samplesMinimize by using large samples
Biological Therapy ExperimentsBiological Therapy Experiments
Can we use viruses that attack bacteria Can we use viruses that attack bacteria (bacteriophages) to fight infections? (bacteriophages) to fight infections?
Experiment 1Experiment 1
Hypothesis - Bacteriophages can protect Hypothesis - Bacteriophages can protect mice against infectious bacteriamice against infectious bacteria
Prediction - Mice injected with Prediction - Mice injected with bacteriophages will not die as a result of bacteriophages will not die as a result of bacterial injectionbacterial injection
Experiment 1 - TestExperiment 1 - Test
• Experimental group Experimental group
Inject with bacteria and Inject with bacteria and bacteriophagebacteriophage
• Control groupControl group
Inject with bacteria and saline Inject with bacteria and saline
Experiment 1 - Experiment 1 - Results & ConclusionResults & Conclusion
Experimental group Experimental group
All mice livedAll mice lived
Control groupControl group
All mice diedAll mice died
Conclusion - Bacteriophage injections Conclusion - Bacteriophage injections
protect mice against bacterial infectionsprotect mice against bacterial infections
Experiment 2Experiment 2
Prediction - Bacteriophage injections will Prediction - Bacteriophage injections will be a more effective treatment than a be a more effective treatment than a single dose of the antibiotic streptomycinsingle dose of the antibiotic streptomycin
Test - Mice injected with bacteria, then Test - Mice injected with bacteria, then with saline, streptomycin, or bacteriophagewith saline, streptomycin, or bacteriophage
Experiment 2 - ResultsExperiment 2 - Results
With 2nd injection:With 2nd injection:
Bacteriophage - 11 of 12 mice livedBacteriophage - 11 of 12 mice lived
60 mg/gm streptomycin - 5 of 12 lived60 mg/gm streptomycin - 5 of 12 lived
100 mg/gm streptomycin - 3 of 12 lived100 mg/gm streptomycin - 3 of 12 lived
Saline - all mice diedSaline - all mice died
Conclusion - Bacteriophage treatment can be as Conclusion - Bacteriophage treatment can be as
good or better than antibiotic treatmentgood or better than antibiotic treatment
Minimizing VariablesMinimizing Variables
All mice were same age and sex, reared All mice were same age and sex, reared under same conditionsunder same conditions
Each mouse in each test group received Each mouse in each test group received exact same treatmentexact same treatment
All mice in control group received same All mice in control group received same amount of salineamount of saline
Variable tested was antibiotic treatment Variable tested was antibiotic treatment versus bacteriophage treatmentversus bacteriophage treatment
p.12
Results Control Group:Some get intestinal cramps
Experimental Group:Some get intestinal cramps
Experiment Control Group:Eats regularpotato chips
Experimental Group:Eats Olestrapotato chips
Fig. 1-10, p.12
HypothesisOlestra® causes intestinal cramps.
PredictionPeople who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra
Conclusion
Percentages are about equal. People who eat potato chips made with Olestra are just as likely to get intestinal cramps as those who eat potato chips made without Olestra.These results do not support the hypothesis.
Scientific TheoryScientific Theory
A hypothesis that has been tested for its A hypothesis that has been tested for its predictive power many times and has not predictive power many times and has not yet been found incorrectyet been found incorrect
Has wide-ranging explanatory powerHas wide-ranging explanatory power Darwin’s theory of evolution by natural Darwin’s theory of evolution by natural
selectionselection The Cell theory - all living things are made of The Cell theory - all living things are made of
cellscells
Scientists Raise QuestionsScientists Raise Questions
The external world, not internal conviction, The external world, not internal conviction,
must be the testing ground for scientific must be the testing ground for scientific
beliefsbeliefs
Limits of ScienceLimits of Science
Scientific approach cannot provide Scientific approach cannot provide answers to subjective questionsanswers to subjective questions
Cannot provide moral, aesthetic, or Cannot provide moral, aesthetic, or philosophical standardsphilosophical standards
Conflict with supernatural beliefs Conflict with supernatural beliefs CopernicusCopernicus DarwinDarwin