Scientific Method by qfAcYv



Scientific Method

Chapter 1: Section 2
How Scientists Work
 How Scientists Work:
    Solving the Problems
 Much of biology deals with solving
 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
 The Scientific Method
         Scientific Method
 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
 C       O
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 T   M   R
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 F   T   I
 C   H   E
     O   W
                 First                  What does the scientist want
                          Question        to learn more about?


                          Research        Gathering of information

Scientific Method          Next

   An Overview                          An “Educated” guess of an
                         Hypothesis      answer to the question

                                            Written and carefully
                         Procedure/        followed step-by-step
                          Method        experiment designed to test
                                               the hypothesis

                                        Information collected during
                              Data            the experiment

                            And                   And

                                         Written description of what
                         Observations     was noticed during the


                                        Was the hypothesis correct
                         Conclusion           or incorrect?
                 First                  What does the scientist want
                          Question        to learn more about?


                          Research        Gathering of information

Scientific Method          Next

   An Overview                          An “Educated” guess of an
                         Hypothesis      answer to the question

                                            Written and carefully
                         Procedure/        followed step-by-step
                          Method        experiment designed to test
                                               the hypothesis

                                        Information collected during
                              Data            the experiment

                            And                   And

                                         Written description of what
                         Observations     was noticed during the


                                        Was the hypothesis correct
                         Conclusion           or incorrect?
S                                          Hypothesis



 E       V                                    Scientific
 N       E                                     Method

 T   M   R
 I   E   V
 F                                             Data
     T   I                                   (Results)
 C   H   E
             Repeat steps 3-7 for competing hypotheses.
     O   W   Competing hypotheses may include revisions
     D       of the original hypothesis suggested by the
             results of the testing process.
 Here is another
  C           O
 example of how the        Make
                                            Form a
                                        Define / Identify
                                        the Problem

 steps may go….         Observations                              Test Hypothesis
                                                                  Perform Experiments

  E           V
 Even though we                                                                 New

  N           E
 show the scientific                    Organize and
 method as a series                     Analyze Data
  T M         R in
 of steps, keep
 mind E new
       that V                                                     NO         Faulty
  F T
 information or
                                     Do Experiments
                                    and Observations

 thinking might
  I                                Support Hypothesis?

 cause a scientist to
  C up andE
 back         repeat                   YES

 stepsO any W
        at    point
 during the process.                                                           Communicate
       D                                                                       Results

                                                    Draw Valid
        Scientific Method
 Let’s break                   Ask Question

  each of these                Do Background
  steps down
                                 Construct                   Think!
  into their                     Hypothesis                Try Again

  individual                     Test with an
                              Analyze Results
                              Draw Conclusion

                                         Hypothesis is False
                  Hypothesis is True
                                          or Partially True

                               Report Results
        1. Observing
           As we all know, frogs have four legs.

 Make an
   See
    something                      What’s up
    unusual                        with these
   Frogs with
    number of
  2. Questioning
 Recognize, state or define the
 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
   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 a statement
   Must be testable or measurable
   Is based on your research
    and previous experience

 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!)
 Some possible explanationsetc.)-
Disease mutation-Music- (hypotheses)
Something outer
Aliens from+ Roll space-
Chemical Else-
Genetic (virus, parasite,
Loud RockRadiation-
            frog deformities:
   for thehypothesis is true, then:
  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
frog pondsnotsimilar deformities
this is Radiation
should show allowed because
                able to                         the
levels of
of should be able to find these same levels to
Wedeformities (frogs with missingchemical can
butdeformitiesor parasitethen, the
You WHY test it??? or...?)
                         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
and should able to use the same parasite to
Weshould be predictions;
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
same ponds should show deformities as well
      5. Experimenting

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

 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.

 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
 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
 Control group: used as a standard of
 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
 In a controlled experiment,
 only one factor is changed at a
   Independent variable:
   the factor that is deliberately
   Dependent variable:
    the factor that the scientist
   wants to observe; it changes
   in response to the
   independent variable
  Variables in Redi’s
 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: Flies produce maggots.
                             Uncovered jars                       Covered jars

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

Manipulated Variables:
gauze covering that
keeps flies away from

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
 Look for trends, patterns,
  and averages
 What does the data show
 Put your data into words
       8. Draw Conclusions
 Restate the hypothesis:
       Example: Flies produce 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 not appearing due to
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
 Redi’s experiment
on insects generation
                          work of other scientists
          Repeating the
 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

 Louis Pasteur further modified the
  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.
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             Can you put these
              steps in order?
2             7              10               6                 8

Define the
              Analyze Data   Report Results

5             1              4                9                 3

               Make an
                              State the           Determine
                              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
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
 If a law ever did not
  apply, then all
  science based
  upon that law would

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