# Scientific Method

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Scientific Method

Chapter 1: Section 2
How Scientists Work
How Scientists Work:
Solving the Problems
 Much of biology deals with solving
problems
 These problems can be environmental,
ecological, health related, etc.
 No matter what types of problems
are being studied, scientists use
the same problem-solving steps
called…
 The Scientific Method
Scientific Method
Definition
 The scientific method is-
 A logical and systematic approach or
process to problem solving.
 An organized way of using evidence
to learn about the natural world.
 According to Wikipedia - Scientific method is a body
of techniques for investigating phenomena and acquiring
new knowledge, as well as for correcting and integrating
previous knowledge. It is based on gathering
observable, empirical and measurable evidence subject
to specific principles of reasoning, the collection of data
through observation and experimentation, and the
formulation and testing of hypotheses.
Scientific Method
Listing the Steps
   Make an Observation
   Define the Problem
   Research the Problem
   State the Hypothesis
   Experiment to test Hypothesis
   Collect and Record Data
   Analyze Data
   Draw Conclusions
   Determine Limitations
   Report Results
If needed, Do more investigation
S
C       O
I
E       V
N       E
T   M   R
I   E   V
F   T   I
I
C   H   E
O   W
D
S
C       O
I
E       V
N       E
T   M   R
I   E   V
F   T   I
I
C   H   E   Repeat steps 3-7 for competing
O   W   hypotheses. (Competing hypotheses
may include revisions of the original
D       hypothesis suggested by the results of
the testing process.)
S
Here is another
C           O
example of how the
I
steps may go….
E           V
Even though we
N           E
show the scientific
method as a series
T M         R in
of steps, keep
I
mind E new
that V
F T
information or
I
thinking might
I
cause a scientist to
H
C up andE
back         repeat
stepsO any W
at    point
during the process.
D
Scientific Method
 Let’s break
each of these
steps down
into their
individual
components:
1. Observing
As we all know, frogs have four legs.

 Make an
observation
 See
something                      What’s up
unusual                        with these
froggies?
 Frogs with
incorrect
number of
legs!
2. Questioning
 Recognize, state or define the
problem
 Must be in the form of a question
 The obvious question is:
 What is causing these deformities?
3. Researching
 Gather information related to the problem
 Read, observe, measure, take samples, etc.
 How frogs normally
develop from eggs
 The % of frogs with the
deformities
 Number of other species in
the pond with deformities
 Previous or new pollutants
in the pond
 Change in amount of UV
(sunlight) exposure on eggs
 Etc.
4. Hypothesizing

 A hypothesis is-
 An educated guess, trial answer, possible
solution, prediction
 Must be an “If…then” statement
 Must be testable or measurable
 Is based on your research
and previous experience
Hypothesizing

 List possible explanations (alternative
know); and on research you have done
 all of the hypotheses must be testable
(no demons allowed!)
Hypothesizing
 Some possible explanationsetc.)-
Disease mutation-Music- (hypotheses)
Something outer
Aliens from+ Roll space-
Chemical Else-
UltravioletPollution-
Genetic (virus, parasite,
frog deformities:
for thehypothesis is true, then:
this
Ifthis hypothesis
IfGenetic mutation is true, then:
Another possibility that we might think of
If this hypothesis is a likely chemical seems
You shouldbe able to find true, disease-causing
should be
Wepredation able to find thethen: pollutant in
Sorry, frog ponds
isChemical or cannibalism, which
the deformed Pollution
If we (forthis explanation for certain kinds
Webe theexample,isolate the chemical from high
parasites) unusually
agent matebe able to measure at the deformed
shouldbedeformed frogs the offspring
You should best is testable,
Okay, UV radiation at deformed frog sites pond
to
frog pondsnotsimilar deformities
should show allowed because
able to                         the
Ultraviolet
levels of
water
of should be able to find these same levels to
Wedeformities (frogs with missingchemical can
butdeformitiesor parasitethen, the
You WHY test it??? or...?)
limbs).
use the parasites in the
Theshould be testable using at minimum:
isthe exact same deformities of isolated
not(virussame kindsthe the lab
itDiseasefrogs toshould beinfairly uniform the
If this
able show that
induce hypothesis is true,
deformed exact
cause the
Rockfind frogs and/ordeformities in
Loudreal)& Roll Music you may havepond
predictable
and should able to use the same parasite to
Scientific
Weshould be predictions;
These
We
lab
The you think evidence that should onlyin the
Can particular deformitiesof deformitiesaffect
induce the exactthat chemical pollution legs on be
Aliens the fact other kinds
critters from outer space their should this
thought ofwith of same predictions based have
Sheesh! else or that other organisms from the
all four limbs equally,
hypothesis? species
been in one
founddamaged or bitten off
labSomething
same ponds should show deformities as well
Writing a Formalized
Hypothesis
Formalized Hypothesis

 A Formalized Hypothesis is a testable
“If …….then…..” statement

 It shows the relationship between the
cause and effect in your experiment.
Formalized Hypothesis

It contains two variables:
Independent Variable

and

Dependent Variable
Independent Variable

 The Independent Variable is the
one the scientist controls.
 It’s what you, the scientist,
changes to cause a
certain effect.
(To smoke or
not smoke)
Dependent Variable

 The Dependent Variable is the one you
measure or observe.
 It’s the effect of the scientist’s change.

Healthy Lungs or Unhealthy Lungs
Formalized Hypothesis
Examples
Examples below show the independent
variable in red and the
dependent variable
in blue.

“If skin cancer is related to ultraviolet light,
then people with a high exposure to UV
light will have a higher frequency of skin
cancer.”
Form a Hypothesis
Using this Problem
Problem or Question:

Does the size of a molecule affect the rate
at which it diffuses (passes) through a
membrane?
Formalized Hypothesis
Example
 If the diffusion rate through a membrane is related to
molecular size, then the smaller the molecule the
faster it will diffuse through a membrane.

Concentrated
Net flow   of solvent     Dilute
solution
solution
Formalized Hypothesis
Example
Does temperature affect leaf color change?
Possible Hypothesis:
“If temperature affects leaf color change,
then exposing the plant to low
temperatures will result in changes in leaf
color.”
** Make Note**

Use the words,
related or affects
when showing the relationship
between the independent and
dependent variables.
Formalized Hypotheses

Practice forming hypotheses with your
partner by completing the worksheet
provided.
5. Experimenting

 Testing the hypothesis
 Pick the hypothesis that makes the most
sense and is
easy to test
 Then design a
controlled
experiment
Experimenting

 Go to the web site for Hartwick College to
see the experiments               and how
the scientific method             was
actually used to find             out the
cause of recently                  found
frog deformities.

 http://www.hartwick.edu/biology/def_frogs/I
ntroduction/Exploration/explore.html
Experimenting
 Let’s look at the text book example of
the Scientific Method using Redi’s
Experiment on Spontaneous Generation
 He was trying to disprove
the idea of Spontaneous
Generation (or actually
that flies came from
maggots which came
from flies)
Francesco Redi (1668)
Stating the Problem
 Example: How do new living
things come into being?
 Spontaneous generation once
commonly accepted
 Redi wanted to show what
caused the appearance of
maggots (and then flies) on meat
Belief based on
prior observations
   If leaf lands on water it becomes a fish
   If bale of hay left in barn it produces mice
   Muddy soil gives rise to frogs
   Meat hung out in the market is the source
of flies
Belief based on
prior observations
 Redi observed that maggots appeared on
meat a few days after flies were on meat
 No microscope = no way to see eggs
 But Redi believed that maggots came
from eggs that were laid by flies
Forming a Hypothesis

Redi’s Hypothesis:
Flies produce maggots.
 How could he test this?
 Through a controlled experiment
Redi’s Controlled
Experiment
 Redi used two groups of jars
 Jars that contained meat and no cover
 Jars that contained meat and gauze cover

Jars with meat
Uncovered jars

Covered jars
Control and Experimental
Groups
 Control group: used as a standard of
comparison
 Experimental group: the group containing
the factor (variable) that has been changed
(manipulated or independent variable)
Two groups
of jars
Uncovered jars

Covered jars
Variables in an Experiment
 Variables- Factors that can be changed
 Controlled Variables- all the variables that
remain constant
 Manipulated Variable- (also called the
Independent Variable)- factor in an
experiment that a scientist purposely changes
 Responding Variable- (also called the
Dependent Variable)- the outcome or results,
factor in an experiment that may change
because of the manipulated variable….
what a scientist wants to observe
Setting up a Controlled
Experiment
 In a controlled experiment,
only one factor is changed at
a time.
 Independent variable:
the factor that is
deliberately changed
 Dependent variable: the
factor that the scientist
wants to observe; it
changes in response to
the independent variable
Variables in Redi’s
Experiment
 Controlled Variables: jars, type of meat,
location, temperature, time
 Manipulated Variables:
gauze covering
that keeps flies
away from meat
1. Which is the control group? Uncovered jars
2. Which is the experimental group?
Covered jars
Two groups of
Jars with meat
Uncovered jars

Covered jars
Redi’s Experiment on Spontaneous Generation
OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.
HYPOTHESIS: If the production of maggots is related to the ability of flies to come into contact
with meat, then preventing flies from coming into contact with the meat will produce no maggots.

PROCEDURE
Uncovered jars                         Covered jars

Controlled Variables:
jars, type of meat,
location, temperature,
time
Several
days pass

Manipulated Variables:
gauze covering that
keeps flies away from
meat

Responding Variable:
whether maggots
appear                     Maggots appear                             No maggots appear

CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous
generation of maggots did not occur.
6. Collect and Record Data
Data: observations and measurements
Types of Recorded Data

 Quantitative - observations that
involve measurements/numbers;
i.e. 3 days, 12 maggots, 4 g, 13 sec,
8 liters
 Qualitative - observations that
do not involve numbers, are of a
descriptive nature
i.e. white maggots covered the
meat, leaves were all wilting
7. Analyze the Data

 Examine data tables,
charts, and graphs
 Examine experimental
notes
 Look for trends, patterns,
and averages
 What does the data show
 Put your data into words
8. Draw Conclusions
 Restate the formalized hypothesis:
 Example: If the production of maggots is related to the
ability of flies to come into contact with meat, then
preventing flies from coming into contact with the meat
will produce no maggots.
 Accept or reject the hypothesis.
 Support your conclusion with specific, numerical data.
 What was Redi’s conclusion?
 Flies lay eggs too small to be seen.
 Maggots found on rotting meat are produced
from the eggs laid by flies.
 Maggots are did not
appear from spontaneous
generation!
9. Determine Limitations
 Scientists look for possible
flaws in their research
 They look for faulty
(inaccurate) data
 They look for experimental
error or bias's
 They decide on the validity
of their results
 They make suggestions for improvement or
raise new questions
10. Publish Results
 Communication is an
essential part of science
 Scientists report their
results in journals,
on the internet, or
at conferences
 This allows their
experiments to be
evaluated and repeated
 Scientists can build on previous
work of other scientists
Repeating the
Investigation
 Sometimes results are unexpected.
Repeat the experiment!
 John Needham challenged Redi’s experiment
and designed his own to show that
spontaneous generation CAN occur under
certain circumstances.
 Lazzaro Spallanzini
designed a slightly
different experiment
to improve on
Needham’s work
Repeating the Experiment
(continued)

 Louis Pasteur further modified the
experiment.
Scientific Method
How Scientists Work
Solving the Problems
The reason scientific work is called
“RE-search” rather than just "search "
is because it is an ongoing process
that often times changes our view of
the natural world. It is subject to
modification in light of new evidence
and new ways of thinking.
S
C
I   M
E   E
N       R
T
T       E
H
I       V
F   O
I
I   D
E
C
W
Can you put these
steps in order?
2             7              10               6                 8

Define the
Analyze Data   Report Results
Problem

5             1              4                9                 3

Make an
State the           Determine
Observation
Hypothesis          Limitations   the Problem
Steps of Scientific
Method in order
1              2              3             4                      5

Make an       Define the                   State the
Observation     Problem       the Problem   Hypothesis

6              7              8             9                 10

Analyze Data                     Determine     Report Results
Limitations
Scientific Theory
 A theory is an
explanation of a set of
related observations
or events based upon
proven hypotheses
and verified multiple
times by detached
groups of researchers
Scientific Law
Scientific Method

 Scientific laws represent
the cornerstone
of scientific discovery
 They must be simple,
true, universal, and
absolute
 If a law ever did not
apply, then all
science based
upon that law would
collapse

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