Scientific Method

							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
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S
 C       O
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 T   M   R
 I   E   V
 F   T   I
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 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
  hypotheses) based on your previous
  experience (what you already
  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,
Loud RockRadiation-
            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
this is Radiation
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
(getare minimalMethod. other already
       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
Let’s think about this.…
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
         made in an experiment
   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
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             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