Scientific
Method
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.
Scientific Method
Listing the Steps
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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
First
Question
What does the scientist want
to learn more about?
Then
Research
Gathering of information
Next
Hypothesis
An “Educated” guess of an
answer to the question
Then
Scientific Method
An Overview
Procedure/
Method
Written and carefully
followed step-by-step
experiment designed to test
the hypothesis
Next
Data
And
Observations
Information collected during
the experiment
And
Written description of what
was noticed during the
experiment
Finally
Conclusion
Was the hypothesis correct
or incorrect?
Scientific Method
Ask Question
 Let’s break
each of these
steps down
into their
individual
components:
Do Background
Research
Construct
Hypothesis
Think!
Try Again
Test with an
Experiment
Analyze Results
Draw Conclusion
Hypothesis is True
Hypothesis is False
or Partially True
Report Results
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
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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
 Independent Variable - (also called the Manipulated
Variable) - factor in an experiment that a scientist
purposely changes
 Dependent Variable- (also called the Responding
Variable) - the outcome or results, factor in an experiment
that may change because of the manipulated variable….
what a scientist wants to measure or observe
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: Flies produce maggots.
PROCEDURE
Covered jars
Uncovered 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
Recording the data
 Setting up a data table
Make a column for each trial, person, or day that you are
measuring. You are measuring your DEPENDENT VARIABLE.
Trial or Day 1
Vertically list as
Group 1
many groups as
you have in this
first column. Each
Group2
group is a
different variation
of your
Group 3
INDEPENDENT
VARIABLE.
 Graphing data
Trial or Day 2
Trial or Day 3
AVERAGE
OF TRIALS
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 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
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
Redi’s experiment
on insects generation
What is the difference
between
• Hypothesis
• Theory
• Law
Introduction to Biology
THE SCOPE OF BIOLOGY
• Biology is the scientific study of life
• Interactions between different kinds of
organisms affect the lives of all
Life’s levels of organization define the scope of
biology
• A structural hierarchy of life, from molecules to
ecosystems, defines the scope of biology
• An ecosystem consists of:
– Biotic factors
• all organisms living in a particular area
– Abiotic factors
• all nonliving physical components of the environment
that affect the organisms
(soil, water)
• At the top of life’s
hierarchy is the
ecosystem
• Ecosystems include:
– all the organisms
in an area, which
make up a
community
– interbreeding
organisms of the
same species, a
population
• Organisms are
made up of:
– organ systems
– organs
– tissues
– cells
– molecules
THE PROCESS OF SCIENCE
Scientists use two main approaches to learn about
nature
• In discovery science, scientists describe some
aspect of the world and use inductive reasoning
to draw general conclusions
– Example: birds migrate
South each year during
colder months
because it is warmer.
• In hypothesis-driven science, scientists use the
“scientific method”
– They propose a hypothesis
– They make deductions leading to predictions
– They then test the hypothesis by seeing if the
predictions come true
With the scientific method, we pose and test
hypotheses
• The main
steps of the
scientific
method
Experimental Design
• Experiments designed to test hypotheses must
be controlled experiments
• Control groups must be tested along with
experimental groups for the meaning of the
results to be clear
• Independent variable
• Dependent variable
EVOLUTION, UNITY, AND DIVERSITY
The diversity of life can be arranged into three
domains
• Grouping organisms by fundamental
features helps make the vast
diversity of life manageable for study
• Scientists classify organisms into a
hierarchy of broader and broader
groups
• Most classification schemes group organisms
into three domains:
– Domain Bacteria
– Domain Archaea
- Domain Eukarya
Unity in diversity: All forms of life have common
features
• All organisms share a set of common features,
signs of unity in life’s vast diversity
– All are made of cells
– All have DNA as
their genetic
blueprint
• These orchids show
the variety possible
within one species
• DNA is made of chemical units called
nucleotides
• Each species has its own nucleotide sequence
Characteristics of Living Things:
• The genetic information in DNA underlies all of
the features that distinguish life from non-life
– Order and regulation (homeostasis)
– Growth and development
– Use of energy from the environment
– Response to environmental stimuli
– Ability to reproduce
– Evolutionary change
Evolution explains the unity and diversity of life
• Charles Darwin is a central figure in
biology
• He synthesized the theory of evolution by
natural selection
– A theory in science is a
comprehensive idea with
broad explanatory power
• Evolution is the core theme
of biology
• The theory of
natural selection
explains the main
mechanism
whereby all species
of organisms
change, or evolve
• Evolution happens when populations of
organisms with inherited variations are
exposed to environmental factors that favor the
success of some individuals over others
– Natural selection is the editing mechanism
– Evolution is based on adaptations
BIOLOGY AND EVERYDAY LIFE
Connection: Biology is connected to our lives in
many ways
• Biology is connected to a great number of
important issues
– Environmental
problems and
solutions
– Genetic engineering
– Medicine
• Many technological advances stem from the
scientific study of life
• Evaluating everyday reports in the press about
a large range of subjects requires critical
thinking and some familiarity with many areas
of biology
Your turn….
1. WAIT for Ms. Allard tell you to turn on
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hit SEND!
4. Do NOT log off until Ms. Allard tells
you to do so!
The ability to move and use oxygen are 2
characteristics of all living things.
A.) true
B.) false
Biology can be related to our every day lives.
A.) true
B.) false
The core theme of biology is
A.) a hierarchy
B.) the scientific method
C.) DNA
D.) evolution
The prefix "a" means
A.) with
B.) without
C.) single or solitary
D.) one
The prefix "bio" means
A.) self
B.) story
C.) life
D.) study of