Themes in the Study of Life

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For example,

Observation: Your flashlight doesn’t work

Question: Why doesn’t your flashlight work?

Hypothesis 1: The batteries are dead

Hypothesis 2: The bulb is burnt out

Both these hypotheses are testable

Slide 101

Fig. 1-24

Observations

Question

Hypothesis #1:

Dead batteries

Hypothesis #2:

Burnt-out bulb

Prediction:

Replacing batteries

will fix problem

Prediction:

Replacing bulb

will fix problem

Test prediction

Test prediction

Test falsifies hypothesis

Test does not falsify hypothesis

Slide 102

Fig. 1-24a

Observations

Question

Hypothesis #1:

Dead batteries

Hypothesis #2:

Burnt-out bulb

Slide 103

Fig. 1-24b

Test prediction

Hypothesis #1:

Dead batteries

Hypothesis #2:

Burnt-out bulb

Test prediction

Prediction:

Replacing batteries

will fix problem

Prediction:

Replacing bulb

will fix problem

Test falsifies hypothesis

Test does not falsify hypothesis

Slide 104

Deduction: The “If…Then” Logic of Hypothesis Based Science

Deductive reasoning uses general premises to make specific predictions

For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction)

Slide 105

A Closer Look at Hypotheses in Scientific Inquiry

A hypothesis must be testable and falsifiable

Hypothesis-based science often makes use of two or more alternative hypotheses

Failure to falsify a hypothesis does not prove that hypothesis

For example, you replace your flashlight bulb, and it now works; this supports the hypothesis that your bulb was burnt out, but does not prove it (perhaps the first bulb was inserted incorrectly)

Slide 106

The Myth of the Scientific Method

The scientific method is an idealized process of inquiry

Hypothesis-based science is based on the “textbook” scientific method but rarely follows all the ordered steps

Discovery science has made important contributions with very little dependence on the so-called scientific method

Slide 107

A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations

Many poisonous species are brightly colored, which warns potential predators

Mimics are harmless species that closely resemble poisonous species