Chapter 2: Science as a Way of Knowing: Critical Thinking about

the Environment

Understanding What Science Is

• Scientific understanding of life and its environment is based on scientific method.

• Science is a process– A way of knowing– Results in conclusions, generalizations and

sometimes laws– Allows us to explain a phenomenon and make

predictions (based on knowledge at the present time)

Science as a way of knowing

• Continuous process– Sometimes a science undergoes a fundamental

revolution in ideas

• Science begins with observations– E.g. How many birds nest at Mono Lake?– What food do they eat?

• Deals only with statements that can be disproved.

Disprovability

• A statement can be said to be scientific if someone can state a method by which it could be disproved.

• Many ways of looking at the world– Distinction between scientific statement and

nonscientific is not a value judgment– Simply a philosophical one

Assumptions of Science

• Events in the natural world follow patterns.• Basic patterns and rules are the same

throughout the universe.• Based on a type of reasoning known as

induction.• Generalizations can be tested and disproved.• New evidence can disprove existing

scientific theories, but can never provide absolute proof.

Deductive reasoning

• Example 1– Premise: a straight line is the shortest distance

between two points.– Premise: The line from A to B is the shortest

distance between points A and B.– Conclusion: Therefore, the line from A to B is a

straight line.

• Proof does not require that the premises be true, only that the reasoning foolproof.

Deductive reasoning

• Example 2– Premise: Humans are

the only toolmaking organisms.

– Premise: the woodpecker finch uses tools.

– Conclusion: Therefore, the woodpecker finch is a human being.

Inductive reasoning

• Science requires not only logical reasoning but also correct premises.

• Generalizations based on a number of observations = inductive reasoning.

Probability

• A way of expressing our certainty– Our estimation of how good our observations are– How confident we are of our predictions

• Scientific reasoning combines induction and deduction

Measurements and Uncertainty

• When we add numbers to our analysis– Obtain another dimension of understanding– Visualize relationships– Make predictions– Analyze strength of relationships

Measurements and Uncertainty

• Measurements are limited– Meaningless unless it is accompanied by an

estimate of its uncertainty.

• Two sources of uncertainty– Real variability in nature– Every measurement has some error– Called experimental error

Accuracy and Precision

• Accuracy refers to what we know.

• Precision refers to how well we measure.

Accuracy versus Precision

• Accuracy refers to the proximity of a measurement to the true value of a quantity.

• Precision refers to the proximity of several measurements to each other.

Observations, Facts, Inferences, and Hypotheses

• Obs. - may be made by any of the five senses or instruments that measure beyond what we sense.

• Inference - a generalization that arises from a set of obs.

• Fact – obs about a particular thing agreed by all

Hypothesis

• Type of statement used– When scientists wish to test an inference– Can be disproved

• If a hypothesis has not been disproved– Is still not proven true– Only found to be probably true

Variables

• Dependent variable – rate of photosynthesis

• Independent variable – amount of light

• Manipulated variable – ind var because can be changed

• Responding variable – dep var because it response to change

Controlled Experiment

• Experiment compared to a standard, or control.– An exact duplicate of the experiment except the

condition of one variable being tested.

• Any difference in outcome attributed to the independent variable.

Repeatability

• Operational definitions – variables described in terms of what one would have to do to duplicate the variable’s measurements.

• Oper. def. allows other scientist to repeat experiments exactly and check results.

Data

• Quantitative- numerical– E.g. diameter of a tree trunk

• Qualitative- nonnumerical– E.g. species of tree

Models and Theories• Scientists use

accumulated knowledge to develop explanations.

• A Model is a “deliberately simplified construct of nature”.

•Models that offer broad, fundamental explanations of observation are called theories.

Scientific Method

• 1. Make observation and develop a question about the obs.

• 2. Develop a tentative answer- a hypothesis.

• 3. Design a controlled experiment to test the hypothesis.

• 4. Collect data.

• 5. Interpret data.

Scientific Method

• 6. Draw a conclusion from the data.• 7. Compare the conclusion to the hypothesis

and determine whether the results support or reject the hypothesis.

• 8. If the hypothesis is supported, conduct additional experiments to test it further. If the hypothesis is rejected, construct a new hypothesis.

Scientific Method

Misunderstandings about Science

• Scientific theory- grand scheme that relates and explains many observations and is supported by a great deal of evidence.

• In everyday usage theory may mean a guess, a hypothesis, a prediction, a notion, a belief.

Science and Technology

• Science is a search for understanding

• Technology is the application of scientific knowledge that benefits humans.

• The two are intertwined.

• In our daily lives most of us do not encounter science but the products of science.

Misunderstandings about Science

• Myth of objectivity or value free science.

• Pseudoscientific– Untestable, lack empirical evidence or based on

faulty reasoning.

• Frontier science– Ideas that may move into realm or science or

pseudoscience.

Environmental Questions and the Scientific Method

• Enviro sciences deal w/ especially complex systems.– Not as neat as the scientific method.

• Different approach has been used in environmental sciences.

• E.g. California Condor

California Condor

• Numbers declined to 22 in the 1970’s

• Suggestions to help populations– Remove all from the wild and breed in zoos– Improve habitat; returning it to grassland

• Population to small to divide into two diff. study groups.– Captive breeding begun

California Condor

• By 1990’s numbers large enough to start reintroductions.

• Today there are 300 condors, 158 in the wild.

• In 2003 first wild chicks fledged.

• Beginning to find there own food.

• Effort appears to be a success.

Historical Evidence

• Frequency of fires in the BWCA of MN.

• Three kinds of data used– Written records– Tree-ring records– Buried records (fossil and pre-fossil org

deposits)

• Fire scars could be seen in record.

Historical Evidence

• By examining cross sections– Possible to determine the date of each fire– Number of years between fires

• Heinselman determined it burned once per century.

• Forests shown to be integral part of forests.

Historical Evidence

• Historical info meets the primary requirement of scientific method– Ability to disprove a statement

• Major source of data that can be used to test hypotheses in ecology.

Modern Catastrophes and Disturbances as Experiments

• Eruption of Mount St Helens in 1980– Allowed for study of dynamics of ecological

systems

• 1988 Wildfire in Yellowstone NP– Carefully monitored before and after.

Learning about Science

• Open-ended process

• Students often perceive science as a body of facts to be memorized.

• Really a set of currently accepted truths, always subject to change.