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