02 Scientific Method

Environment & Ecology

The nature of science• Science:

– A systematic process for learning about the world and testing our understanding of it

– The accumulated body of knowledge that results from a dynamic process of observation, testing, and discovery

• Science is essential:– To sort fact from fiction – Develop solutions to the problems we face

Vaccines cause autism

Fact or Fiction?

Global Warming

Fact or Fiction?

Discovery or observational science.

Hypothesis-driven or experimental science.

Two Primary Approaches to ScienceScientists test ideas

Hypothesis-Driven Studies

Discovery/Observational Studies

Applications of science

Restoration of forest ecosystems altered by human suppression of fire

Policy decisions and management practices

Energy-efficient methanol-powered fuel cell car from DaimlerChrysler

Technology

The scientific method

• Observations • Question • Formulate Hypothesis • Conduct Experiment • Analyze Results • Conclusions • Discussion

A technique for testing ideas

Testing predictions• Experiment: an activity that tests the validity of a

hypothesis• Variables: conditions that can be manipulated

and/or measured– Independent variable: a condition that is manipulated– Dependent variable: a variable that is affected by the

manipulation of the independent variable• Controlled experiment: one in which all variables

are controlled– Control: the unmanipulated point of comparison– Treatment: the manipulated point of comparison

• Data: information that is generally quantitative (numerical)

Experiments test the validity of a hypothesis

• Manipulative experiments yield the strongest evidence– Provides the strongest type of evidence– Reveal causal relationships: changes in independent

variables cause changes in dependent variables– But many things can’t be manipulated: long-term or

large-scale questions (i.e., global climate change) • Natural experiments show real-world complexity

– Only feasible approach for ecosystem or planet-scale– Results are not so neat and clean, so answers aren’t

simply black and white

Scientific Method: ExampleExample

Many habitats are fragmented.

Corridors are being constructed between patches.

Do they really work?

Observations

Scientific Method: ExampleExample

Corridors facilitate movement of butterflies between isolated habitat patches

Common buckeye Variegated fritillary

Hypothesis

Butterflies will move into connected habitat patches more frequently than into unconnected habitat patches

Prediction

Experiment and/or data collection

Experiment results

Observation:

Question:

Hypothesis:

Test hypothesis:

Analyze Results:

Draw Conclusion:

Ben Franklin & the Gulf Stream

1996

1786

Pisaster

Paine’s study on Pisaster and blue musselsWhat effect does starfish removal have on community structure?

chiton limpet

mussels (Mytilus)

barnacles

Keystone Species

Paine’s study on Pisaster and blue mussels

Coral Reef Benthic Habitat Point and Area

AssessmentsKaneohe Bay, HI

• Large sample size• Random sampling

Mangrove Study

Do sponges affect mangrove root growth?

Select a large sample size

Randomly divide the sample into 2 groups

Treat the groups equally in all ways but oneObserve or make measurements

Compare results

Mangrove Study

Inquiry1. What is the difference between a

hypothesis, theory and law?2. Can a theory ever be proven?3. In the mangrove study, what is the

dependant variable?4. State Ben Franklin’s hypothesis.5. In Paine’s study on Pisaster, what

role did blue mussels play?

QUESTION: Review

Which is the correct order of the scientific method?

a) Observation, question, hypothesis, testing, results

b) Hypothesis, observation, testing, question, results

c) Observation, question, testing, results, hypothesis

d) Question, observation, hypothesis, testing, results

QUESTION: Interpreting Graphs and Data

What happens if test results reject a hypothesis?

a)The scientist formulates a new hypothesis.

b) It shows the test failed.c) The scientist should be fired.d)The scientist used faulty data .