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The Process of LifeScientific Method

+Observation

Scientists believe: That nature is orderly and measurable That natural laws do not change over time OBSERVATION explains phenomena This principle is called: NATURAL CAUSALITY

BUT WAIT- don’t forget there’s always CHANCE!!

Alexander Flemings discovery of penicillin

How keen are your observations?

You have one minuteTo observe the picture and formulate a hypothesis about what happened

+Hypothesis

How do I make this guess?????

INDUCTIVE vs. DEDUCTIVE Reasoning Inductive reasoning: bottom up approach-

observations are made from SPECIFIC TO GENERAL

Deductive reasoning: top-down approach- observations are made from GENERAL TO SPECIFIC

An educated guess

+Inductive Reasoning

Jill is a teacher All teachers are smart Therefore Jill is smart

Allows observer to move from SPECIFIC TO GENERAL

+Deductive Reasoning

Every vertebrate has a backbone

Cows are vertebrates Cows have backbones

Allows observer to move from GENERAL to SPECIFIC

MOOOOOO

I am a SYLLOGISM – The Syllogism is a specific form of argument that has three easy steps.

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_____ Bluebird songs are beautiful._____ Only male bluebirds sing. _____ Sparrows will leave territories where they hear bluebird songs._____ Bluebirds hate sparrows.

A hypothesis must be testable

Can these be tested?

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ExperimentsAn experimental design is proposed that tests the hypothesis

Using DEDUCTIVE REASONING scientists formulate an IF…. THENStatement

IF I shake this really hard, THEN I might explode!

+Experiments consist of A control group

Independent variables – a factor that causes an observable change in other variables

Example: someone's age. Other factors (such as what they eat, how much they go to school, how much television they watch) aren't going to change a person's age.

Dependent variables – changes DUE to other factors Example: a test score, because it could change depending on

several factors such as how much you studied, how much sleep you got the night before you took the test, or even how hungry you were when you took it.

(Independent variable) causes a change in (Dependent Variable) and it isn't possible that (Dependent Variable) could cause a change in (Independent Variable).

+DATA DATA DATA DATA DATA Observable Measurable Does the DATA show any probability of chance? This is called a

“measure of SIGNIFICANCE”

OH NO – Not STATISTICS!! Statistical significance is the number, called a p-value, that

tells you the probability of your result being observed, given that a certain statement (the null hypothesis) is true. If this p-value is sufficiently small, the experimenter can safely assume that the null hypothesis is false.

You roll two dice, they both turn up one. This does not fit your hypothesis that you would only roll a one, 1 out of 6 times. Is your data SIGNIFICANT enough to change your prediction?

+Conclusion

Does the date SUPPORT or REJECT the hypothesis?

Can I repeat my experiment?

The conclusion of 1 experiment can lead to the beginning of another!

Communicate the results!!

+OK, so What’s the Point of all this? The ultimate goal is to understand the world, using

data to support our observations We call this a:

SCIENTIFIC THEORY or a SCIENTIFIC PRINCIPLE Let’s look at some well know theories:

Cell theory Heliocentric theory

Evolution Gene theory

Theory of gravity Germ theory

+Theory vs. Law

Theories become laws---NO—theories explain sets of data (the why)

Laws provide general rules for what we expect to happen (the what)

A theory IS NOT a lesser form of a law! Theories :

1. Must explain a wide range of observations

2. Must be falsifiable

3. can be changed if new evidence presents itself

scientists do not "believe" in something. Instead, they have levels of confidence in explanations for natural phenomena.

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Occam's Razor

One last tid-bit!

proposed by William Ockham in the 15th century.

The simplest explanation is usually the right one!

A paper clip is placed on a scale, the scale reads 600 pounds. The following hypotheses can be proposed:

•The paperclip weighs 600 pounds•The scale is broken•There is a miniature black hole producing a gravitational pull on the paperclip at that moment, creating such a force to make the paperclip weigh 600 pounds