What is Science?
• Common sense raised to a higher level and
applied systematically
• A “way of knowing”
Other “Ways of Knowing”
Characteristics of Science
1) Guided by natural laws
2) Explained in reference to natural law
3) Things (results, conclusions) are falsifiable
Types of Science
1) Discovery Science
2) Hypothesis-Driven Science
Discovery Science
•
Goal = find natural cause of natural phenomena;
descriptions
•
•
structure and process of observable things
e.g., mapping the human genome; finding
and describing a new species
relies on inductive reasoning
•
Scientific Reasoning
•
Induction: “…elementary my dear Watson….”
•
Deduction: (hypothetico-deductive
reasoning) =
•
If all organisms are made of cells AND
Humans are organisms, THEN
Humans are made of cells
Hypothesis-Driven Science
•
•
•
Follows a set process (scientific method)
Relies on deductive reasoning
Relies on hypothesis formation &
experimentation
Process of Science
• Scientific method: means by which a
scientist seeks to gain new knowledge or
explain natural phenomenon
Process of Science
1) Observe a problem
2) Recognize a problem
3) State an hypothesis (tentative answer to
problem to which a prediction should
follow)
4) Conduct an experiment (=test prediction)
5) Postulate theory (a comprehensive
explanation for a pattern of broad scope
based on large data set)
Reject
Fail to Reject
Process of Science
Observations
Process of Science
Question
• So what? …. Why would snowberry flies
look like their predator?
Hypothesis
Prediction
Why a Control Group?
• Allows honing into causative factors by reducing
variance of other explanations
Take-home message 1.4
 The
scientific method (observation,
hypothesis, prediction, test, and conclusion) is
a flexible, adaptable, and efficient pathway to
understanding the world because it tells us
when we must change our beliefs.
1.5 Step 1: Make
observations.
Look for interesting
patterns or cause-andeffect relationships.
Does taking echinacea reduce the intensity or
duration of the common cold?
1.6 Step 2: Formulate a
hypothesis.
A proposed explanation for
observed phenomena
To be most useful, a hypothesis must
accomplish two things:
The Null Hypothesis

A negative statement that proposes
that there is no relationship between two
factors

These hypotheses are equally valid but are
easier to disprove.

An alternative hypothesis

It is impossible to prove a hypothesis is
absolutely and permanently true.
Null and Alternative
Hypotheses
 Echinacea
reduces the duration and
severity of the symptoms of the
common cold.
Or as a null hypothesis:
• Echinacea has no effect on the duration or
severity of the symptoms of the common
cold.
1.7 Step 3: Devise a
testable prediction.
Suggest that under certain
conditions we will make
certain observations.
Devising a Testable Prediction
from a Hypothesis
The goal is to:
Hypothesis: Echinacea reduces the duration and
severity of the symptoms of the common cold.
1.8 Step 4: Conduct a
critical experiment.
an experiment that makes it
possible to decisively determine
whether a particular hypothesis is
correct
Hypothesis: Echinacea
reduces the duration and
severity of the symptoms
of the common cold.
1.9 Step 5: Draw
conclusions, make revisions.
Trial and error
The Role of Experiments
 What
is important is that we attempt to
demonstrate that our initial hypothesis is
not supported by the data.

Making Revisions
 Try
to further refine a hypothesis.
 Make
new and more specific testable
predictions.
Does echinacea help prevent the common cold?
Hypothesis: Echinacea reduces the duration and
severity of the symptoms of the common cold.
Take-home message 1.9
Process of Science
Hypothesis vs. Theory
* Gray wolves form
packs to increase
their efficiency in
securing food.
* Pack formation in
many species has
evolved via natural
selection.
Scientific Theory
• An explanation of the causes of a wide
range of related phenomena
Limits of Science
Scientists Raise Questions
The external world, not internal conviction,
must be the testing ground for scientific
beliefs
• Read Street Bio, p 30