Transcript Powerpoint Scientific Method

Chapter 1
Scientific Method
Chapter 1.4 - The Process of Life
A. Scientific Method
The general process of science is said to be characterized by a
sequence of stages. (The Scientific Method!)
B. Observation
1. Scientists believe nature is orderly and measurable.
2. Science also considers that natural laws do not change with time.
3. Phenomena can therefore be understood from observations.
Let’s Test Your Observation Skills
Can you find the 5 differences?
*This principle of science is
known as NATURAL
CAUSALITY, by its nature it
excludes supernatural
phenomenon*
What are some things that are
considered supernatural?
Shows like ghost hunters only “pretend” to be scientific.
Why is it impossible to truly study this phenomenon?
The Case of the Slithering Rocks
To truly study a mysterious phenomenon, that phenomenon must be
repeatable and observable. This rock seemed to move on its own across the
desert. The explanation turns out to be a NATURAL ONE.
Inductive reasoning allows a person to combine isolated facts
into a cohesive whole, reasoning makes broad generalizations
from specific observations.
Observation 1: Snakes have tiny pelvic bones
Observation 2: Snakes and lizards have similar DNA sequences
Observation 3: Snakes appear after lizards in the fossil record.
Generalization: Snakes are related to lizards / Snakes evolved from lizards
This type of reasoning can
result in the development of
a HYPOTHESIS.
A hypothesis is a possible explanation for a natural
event or a series of observations
- to be valid, the hypothesis must be testable.
Examples of hypotheses, check those that
are valid and can be tested
_____Bluebirds sing to attract mates.
_____ Bluebird songs are beautiful.
_____ Only male bluebirds sing.
_____ Sparrows will leave territories where
they hear bluebird songs..
_____ Bluebirds hate sparrows.
Create Your Own Hypothesis
Experiments/Further Observations
Deductive reasoning involves “if, then” logic that predicts what
will happen based on the hypothesis or theory.
Involves general RULES to make predictions.
Start with a general idea or principle → use that to make
predictions.
1. All living things require energy
2. Bacteria are living things
3. Bacteria require energy
Prediction: Bacteria deprived of an energy source will die.
One of the most common and useful forms of deductive
reasoning is the syllogism. The syllogism is a specific
form of argument that has three easy steps.
1. Every X has the characteristic Y.
2. This thing is X.
3. Therefore, this thing has the characteristic Y.
1. Every vertebrate has a backbone
2. Cows are vertebrates.
3. Cows have backbones.
Consider the nanobacteria study
and how syllogisms were used.
Comparing Inductive and Deductive Reasoning
These graphics shows
what kind of reasoning?
Both inductive reasoning and deductive reasoning are used in the
scientific process.
FALSIFIABILITY
It is important than any statement or hypothesis is falsifiable - if
there is no evidence out there that would prove the statement
wrong, then there is no point in running any tests.
It is bad science to ask someone to
PROVE A NEGATIVE.
For example:
Prove that ghosts don’t exist.
Prove that cell phones don’t cause cancer.
Prove that there are no aliens.
Prove that telepathy doesn’t exist.
The burden of proof lies on the claimant. If you make a claim,
then you must be the one to provide evidence for that claim.
(It is not on other people to show it to be false.)
E. Data
Often the data must be inspected for the probability the data
could show a relationship by chance;
this is a measure of “significance.”
You roll two dice, they both turn
up ONEs. This does not fit your
prediction that you will only roll a
ONE 1 out of 6 times. Is the
data significant enough to
change your prediction?
What is an anecdote?
Anecdotes are singular observations, stories people
tell, or things someone might have heard.
It is NOT data.
F. Conclusion
1. Whether the data support or reject the hypothesis is the basis for
the “conclusion.” - avoid the word "prove"
2. Science findings are reported in scientific journals so results are
available to the research community (peer review).
3. The experiments and observations must be repeatable or the
research is suspect.
The Importance of Publication
After scientists have conducted research, in order for the conclusions
to be considered valid, they must publish their findings in a PEERREVIEWED journal
Peer review means that other scientists will look at their experiment,
design, data, and conclusions and determine if they think the
research is valid.
Check out PLOS for a
source of open-source,
peer reviewed science
articles.
JAMA - Journal of the
American Medical
Association
Let's Recap the Important Points
1. Hypothesis
2. Data Collection
3. Conclusions
-----------------------General Logic Stuff -------------------Inductive versus Deductive Reasoning
Falsifiability
Syllogism
Natural Causation
In your own words (or with a graphic) explain
the difference between deductive and
inductive reasoning.
G. Scientific Theory
The ultimate goal is to understand the natural world in scientific
theories, and conceptual schemes supported by a broad range
of data.
Say What?
Dissect that sentence....what does it really mean?
2. The terms “principle” and “law” are also used
for generally accepted theories.
Basic theories of biology are:
a. Cell theory
b. Biogenesis theory
c. Evolution theory
d. Gene theory
e. Germ Theory
Other Theories
f. Heliocentric Theory
g. Theory of Gravity
Theories can be changed if new evidence presents itself.
Much of our understanding of science has changed over the years as our
technology has gotten better.
What is the difference between a theory and a law?
Theories do not become LAWS.
Theories explain sets of data. (WHY)
Laws provide general rules for what we expect to happen. (WHAT)
Why isn't creationism considered a theory?
Keeping in mind that there is nothing wrong with religious
beliefs, things like creationism are not
considered scientific because they do not meet the criteria
of a scientific theory itself.
1. Creationism -tells- us what happened, and doesn't explain
how, when, why or through what mechanism
2. Creationism cannot be proven false - ie, you cannot
disprove the existence of a divine creation
3. The nature of creationism means that the primary tenant
(divine creation) can never be changed, much for the same
reason you can't disprove it.
4. Not based on natural causes (natural causality)
H. A Controlled Study
1. Some investigations are managed where conditions can
be kept constant
a. A variable is a factor that can cause an observable
change
b. The experimental variable is the step that is
deliberately manipulated (what you changed).
c. A dependent variable is what you measure (the
results).
Examples of experimental (independent) and dependent variables
Question: Does colored light affect plant growth?
What is the experimental variable?
What is the dependent variable?
What variables
must be kept
constant - or
controlled?
Example of a Controlled Study
Observation: Babies are born with severe birth defects,
mothers of these babies report taking the drug thalidomide
during pregnancy for morning sickness.
Question: Does thalidomide cause birth defects?
Hypothesis: Thalidomide causes birth defects.
Experiment:
Control group: Mice not given thalidomide during pregnancy
Variable: Mice given thalidomide during pregnancy
In this experiment, mice born from both the control and
variable group will not have birth defects. This experiment
was performed long before thalidomide was marketed and
prescribed to pregnant women.
Does these mean that
the hypothesis is not
supported?
What is confirmation bias?
What are ways scientists can reduce bias?
What is a double blind experiment?
Scientific Method Scenarios - design an experiment (controls,
variables, set-up), include ways you could reduce bias in the
experiment
Identify dependent and independent variables
Suggest alternative and null hypothesis.
Each table will get their own question to discuss.
A Field Study
Example: male bluebirds act aggessively toward other male bluebirds.
Question: Will they act aggressively toward birds of a different species?
Researchers can place a model of a different bird near the nest to answer the
question.
What is Occam's
Razor?
Ockham's Razor (Occam is
the latinized and more
common spelling) is a
principle proposed by William
Ockahm in the 15th century.
The original principle stated
"Pluralitas non est ponenda
sine neccesitate" which
translates as "entities should
not be multiplied
unnecessarily"
Simply put: The simplest explanation is usually the correct one.
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