Scientific MethodScientific Method

GoalGoal What is the scientific What is the scientific

method?method? Does the scientific method Does the scientific method

work?work? What is not a scientific What is not a scientific

argument.argument. Does biology follow the Does biology follow the

scientific method?scientific method?

Steps in the Scientific Steps in the Scientific MethodMethod

ObservationObservation HypothesisHypothesis

__________________________ ExperimentExperiment

__________________________ ConclusionConclusion

__________________________

Everyday ScienceScientific Method Car Repair

Observation Engine won’t turn over.Hypothesis (_________________)

Predict battery is dead.

Test (_______________) Replace battery.Observe result Engine now turns over.Revise hypothesis? Not needed.New test? Not needed.Scientific Theory Cars won’t work

without a fully charged battery.

Everyday ScienceScientific Method Making Spaghetti Sauce

Observation Spaghetti sauce is made of tomatoes.

Hypothesis (prediction)

Try to make tomato sauce with whole tomatoes.

Test Heat pot of tomatoes.Observe result Taste the sauce – yuck.Revise hypothesis? Use tomato sauce and

garlic!New test? Add garlic, taste - not so

bland.Scientific Theory The Final Recipe.

ObservationsObservations Gathered Gathered through your through your

__________________ A scientist A scientist

notices notices (wonders (wonders

about) about) something in something in

their their ____________________________

ObservationsObservations An An exampleexample of a of a

scientific scientific observationobservation

might be might be noticing that noticing that

many many salamanders salamanders

near a pond have near a pond have curved, not curved, not

straight, tailsstraight, tails

HypothesisHypothesis A suggested A suggested

solution to (reason solution to (reason for) the problem or for) the problem or observationobservation An ____________An ____________

Must be Must be ________________ Sometimes written Sometimes written

as as If…Then…If…Then… statementsstatements

______________________an an outcomeoutcome

HypothesisHypothesis An An example of a example of a

hypothesishypothesis might might be that the be that the salamanders salamanders have curved tails have curved tails due to a pollutant due to a pollutant in the moist soil in the moist soil where they livewhere they live

ExperimentExperiment

An An Experiment Experiment is a _________ is a _________

set up to set up to testtest the the

hypothesis.hypothesis.

ExperimentExperiment

VariableVariable – – factor in the factor in the experiment experiment that is being that is being

testedtested

ExperimentExperiment A good A good (valid) (valid)

science science experiment experiment tests a tests a single single variablevariable that that can be can be measured measured against a against a control.control.

ExperimentExperiment Controlled Controlled

experiments experiments are are situations where situations where all factors are the all factors are the same between two same between two test subjects, test subjects, except for the except for the single __________single ______________________________________

ExperimentExperimentThe The

independent independent variable variable is the is the

____________________________________ in ____________ in

the the experimentexperiment

Scientific Experiments Scientific Experiments Follow RulesFollow Rules

An experimenter ______________________

and observes or measures what happens.

Variables Remember, the factor that is

changed is known as the _______________________.

The factor that is measured or observed is called the _______________________. (What “happens” DEPENDS on what the

experimenter changed!)

What is the Purpose of What is the Purpose of a Control?a Control?

Controls are NOT being tested

Controls are used for COMPARISON

Example of Controls & Example of Controls & VariablesVariables

For example, suppose you want to figure out the fastest route to walk home from school.

You will try several different routes and time how long it takes you to get home by each one.

Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

What are the Variables What are the Variables in Your Experiment?in Your Experiment?

Varying (changing) the route Varying (changing) the route is the is the independent variableindependent variable

The time it takes is the The time it takes is the dependent variabledependent variable

Keeping the same walker Keeping the same walker throughout makes the throughout makes the walker a walker a control variable.control variable.

One more thing… it is best to make several trials with each independent variable.

Valid ExperimentsValid Experiments Two groups are required

--- the control & experimental groups

There should be only one variable

DataData Results of

the experiment

May be quantitative (numbers) or qualitative

DataData Must be

organized Can be

organized into charts, tables, or graphs

ConclusionConclusion

The answer to the hypothesis based on the data obtained from the experiment

RetestRetest

In order to verify the results,

experiments must be retested

So?????? A successful

hypothesis eventually becomes a Scientific Theory.

TheoriesTheories A theory is a highly successful A theory is a highly successful

hypothesis.hypothesis. All hypotheses make predictions.All hypotheses make predictions. All theories make predictions.All theories make predictions. All theories can be tested.All theories can be tested. Result: Any scientific theory is Result: Any scientific theory is

subject to change as our ability to subject to change as our ability to make tests, or make observations of make tests, or make observations of a test’s results, improves with time.a test’s results, improves with time.

Non-scientific TheoriesNon-scientific Theories Make no predictionsMake no predictions Un-testableUn-testable Can’t be provenCan’t be proven

Non-scientific TheoriesNon-scientific Theories Car won’t work? Car won’t work? Aliens drained the Aliens drained the

battery.battery. Spaghetti is bland? Spaghetti is bland? You were meant to You were meant to

eat bland food.eat bland food. Car won’t work? Car won’t work? Gods must be angry. Gods must be angry. Spaghetti is bland? Spaghetti is bland? At the instant of At the instant of

tasting, the tongue is transported to tasting, the tongue is transported to alternate dimension where all flavors are alternate dimension where all flavors are rendered nullified. Happens rendered nullified. Happens instantaneously.instantaneously.