The Science of Biology
Chapter 2
• What is science?
A body of knowledge and a process in which we try to understand how the
natural world works using the scientific method.
• Science presumes that objects/events in the universe occur in
consistent patterns that are able to be understood.
• Only observable/measureable occurrences are open to scientific
investigation.
• Science only deals with natural phenomena-science cannot provide
answers to personal opinions, beliefs, superstitions, myths,
predictions of the future, and does not use supernatural beings as an
explanation for events.
• This knowledge is always growing and changing as scientists ask
new questions and explore new ideas and as better tools and
technology are developed.
Types of Inquiry
Discovery-Based Science- observing and
describing phenomena in the natural world
(example: field-based studies)
Hypothesis-Based Science- using the
scientific method (controlled experiments) to
explain phenomena in the natural world
(example: lab experiments)
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Lab
experiments
Hypothesis
Based
Science
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Careful
Observation
Leads to
Lab
experiments
Hypothesis
Based
Science
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Lab
experiments
Careful
Observation
Leads to
Data
Collection
Hypothesis
Based
Science
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Lab
experiments
Careful
Observation
Leads to
General conclusions
based on specific
observations
Inductive Reasoning
(specific to general)
Data
Collection
Hypothesis
Based
Science
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Careful
Observation
Lab
experiments
General Idea/
Observation
Leads to
General conclusions
based on specific
observations
Inductive Reasoning
(specific to general)
Data
Collection
Hypothesis
Based
Science
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Careful
Observation
Lab
experiments
General Idea/
Observation
Hypothesis
Based
Science
Specific
Question
Leads to
General conclusions
based on specific
observations
Inductive Reasoning
(specific to general)
Data
Collection
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Careful
Observation
Lab
experiments
General Idea/
Observation
Hypothesis
Based
Science
Specific
Question
Leads to
General conclusions
based on specific
observations
Inductive Reasoning
(specific to general)
Data
Collection
Possible answer
(hypothesis)
Approaches to Biological Inquiry
Field-based
studies
Discovery
Based
Science
Careful
Observation
Lab
experiments
General Idea/
Observation
Hypothesis
Based
Science
Specific
Question
Leads to
General conclusions
based on specific
observations
Inductive Reasoning
(specific to general)
Data
Collection
Possible answer
(hypothesis)
Predict what will happen if
tested in an experiment
Approaches to Biological Inquiry
Lab
experiments
Field-based
studies
Discovery
Based
Science
1
General Idea/
Observation
Careful
Observation
1
Hypothesis
Based
Science
Specific
Question 2
Leads to
2
General conclusions
based on specific
observations
Inductive Reasoning
(specific to general) 3
2
5
Data
Collection
6 Specific conclusions based
data regarding a general idea
Deductive Reasoning
(general to specific)
Possible answer
(hypothesis)
3
Predict what will happen
4
if tested in experiment
Types of Data
(recorded observations)
•
•
•
•
•
Descriptions
Sketches
Photographs
Journals
Movies
•
•
•
•
Lead
to
Measurements in metrics
Counts
Number based data tables
Graphs
Leads
to
experiment
Allows
you to
make
How are inferences different
from observations?
How are generalizations
different from inferences?
Observation vs. Inference
•
Make one
qualitative
observation.
• Make an
inference from
that
observation.
• Make one
quantitative
observation.
• Make an
inference from
that
observation.
• Make an
observation
regarding what
is absent from
the picture.
• Make an
inference from
that
observation.
What you don’t see can be important as what you do see!
Regarding
observable/measurable occurrences in
the natural world.
Make
observations and research your topic of
interest. Gather information.
Make a general statement an “educated
guess” that will guide you in the design
of your experiment .
– A hypothesis must be falsifiable (disprovable): able to be
proven false.
– Science advances by disproving hypotheses.
– You CANNOT prove a hypothesis true!
– Future observations can always disprove your conclusion
made today.
– Supported hypotheses are conditionally accepted for the
time being only. (tentative)
“No number of experiments can prove me right;
a single experiment can prove me wrong.”
Albert Einstein
Scientific Inquiry: a closer look…
Formulate a
statement that shows the relationship
between the variables in your
experiment. (more specific than a
hypothesis)
Use an “If….then…” format.
Example: If I increase the temperature,
then plant growth will increase.
Scientific Inquiry:a closer look…
Develop and follow a
procedure.
• Include a detailed materials list.
• The outcome must be
measurable/observable (quantifiable).
• Modify the procedure if needed.
• Confirm the results by retesting.
Scientific Inquiry:a closer look…
Include a statement that
accepts or rejects the hypothesis.
– Make recommendations for further study
and possible improvements to the
procedure.
Present the
project to an audience.
• Peer Review-Publish the results in a Journal
to be reviewed and retested by your peers.
Hypothesis Based Science
(The Scientific Method)
Curiosity/Observing the world around you
Problem/Question
Observations/Research
Hypothesis
Test additional
predictions
based on the
same
hypothesis
Prediction
Experiment
Revise
hypothesis
or make a
new one
Collect/Analyze Data
Results
support
hypothesis
Conclusion
Communicate Results
Results
do not
support
hypothesis
Let’s put our knowledge of
the Scientific Method to a
realistic example that
includes some of the terms
you’ll be needing to use and
understand.
Question or Problem:
John watches his grandmother
bake bread. He ask his
grandmother what makes the
bread rise.
She explains that yeast releases
a gas as it feeds on sugar.
John wonders “Does the amount
of sugar used in the recipe
affect the size of the bread
loaf”?
Be careful how you use
and
is usually a noun and
,a
verb.
“ The
of sugar amounts on the
rising of bread.”
“How does sugar
the rising of
bread?”
Observation/Research
John researches the
areas of baking and
fermentation and tries to
come up with a way to
test his question.
He keeps all of his
information on this topic
in a journal.
Why is researching the topic an important step?
Formulate a Hypothesis
After completing his
research, John
hypothesizes that
“the amount of
sugar in the bread
will have an effect
on the loaf’s size”.
Making a plan….
• John talks with his
teacher and she
gives him a
Experimental
Design Diagram to
help him set up his
investigation.
General Layout for an Experimental Design Diagram
Title
The Effect of
on
(independent variable)
(dependent variable)
Hypothesis
Prediction
If
(planned change in independent variable), then
(predicted change in dependent variable).
Independent Variable
Levels of Treatment for Independent Variable and Number of Repeated
Trials
Level 1 (Control)
Level 2
Level 3
Level 4
Number of Trials
Number of Trials
Number of Trials
Number of Trials
Dependent Variable and How Measured
Constants (Standardized Variables)
1.
2.
3.
4.
5.
6.
Formulate a Prediction
After talking with his teacher
and conducting further
research, he comes up
with a prediction.
“If my hypothesis is correct,
then the more sugar I
add, the higher the bread
will rise.”
Why is making a prediction an important step?
The prediction is an educated
guess that states the relationship
between the independent and
dependent variables.
Note: These variables will be defined in the next few slides.
Do you know the
difference between
the independent and
dependent variables?
Types of Variables…
Independent Variable (IV)
• The manipulated variable. The
factor that is intentionally
varied by the experimenter.
• John’s IV is:
amount of sugar
• John is going to use different
Levels of Treatment in his
experiment
(amounts of the IV that will be
tested).
• John is going to test 25g,
50g, 100g, 250g, & 500g of
sugar.
How many independent variables can
you have in an experiment? Explain.
Dependent Variable (DV)
The responding variable. It is
the factor that may change
as a result of changes made
in the IV. It is the variable
that the experimenter will
measure, or count, and then
record.
In this case, the DV would be:
the size of the loaf of bread.
What are some ways that you can
measure the “size” of the loaf?
John decides to use volume as a
way to measure size.
Experiment
His teacher helps him
come up with a
procedure and list of
needed materials.
She discusses with John
how to determine the
control group.
Control Group
In a scientific experiment, the control is the group
that serves as the standard of comparison.
The control group may be a
“no treatment" group (no IV)
or
an “experimenter selected” group.
(a normal amount of the IV)
• It allows the experimenter to determine if and what affect the
Independent variable had on the Dependent variable.
How does this control group differ
from John’s?
Because his grandmother
always used 50g of sugar
in her recipe, John is going
to use that amount in his
control group.
Why not use 0g of sugar as the control group?
Why is it important to have a control group?
Experimental Group(s)…
• The groups of subjects that get the different levels
of treatment (of the IV) other than the Control group
amount.
• What are the Experimental Groups in John’s
experiment? (LOT)
The control group is
• 25g
exposed to the same
• 100g
conditions as the
• 250g and
experimental
• 500g of sugar
group(s), except for
the independent
variable being tested.
Constants/Standardized Variables
John’s teacher reminds him
that there are other factors
(that could affect the
results). They should be
kept the same for all test
subjects so that any
observed changes in the
bread can be attributed to
the variation in the amount
of sugar.
Can you think of
some constants
(SV) for this
experiment?
John’s constants were…
o
o
o
o
o
o
o
o
other ingredients to the recipe
oven used
rise time
brand of ingredients
cooking time
type of pan used
air temperature
humidity where the bread was
rising
o oven temperature
o age of the yeast…
Then…
John writes out his
procedure for his
experiment along
with a materials list
in his journal. He
has both of these
checked by his
teacher where she
checks for any
safety concerns.
How does the control group compare to the experimental group(s)?
What is a “placebo”?
Verifying the Data
More than one measurement is needed for each level of treatment
in order to determine if the data is consistent/reliable
Replication- repeating the
experiment and/or
increasing the number of
tested subjects to give you
more data to analyze (to
check reliability)
Trial- each time the
experiment is repeated
Sample size- number of
subjects per trial
Valid- experiment is
appropriately designed
John’s Experiment:
John is going to run his
experiment 1 time and test
each sugar amount 3 times.
(trials = ?)
(sample size = ?)
Why is replication an important
component of any experiment?
Why is it important that an
experiment produce reliable
results?
How is reliability(consistency of
results) related to validity
(design)?
Running the Experiment
John comes up with a data
table he can use to record
his data.
John gets all his materials
together and carries out
his experiment
Can you tell
which group
did the best?
One row for each level
of treatment
Independent
Variable
(units)
Dependent Variable (units)
One column for each trial or subject
Calculation column
Size of Baked Bread (LxWxH) cm3
Size of Bread Loaf (cm3)
Amount
of
Sugar
(g)
Trials/Subjects
Average
1
2
3
Why calculate
an average?
25
768
744
761
758
50
1296
1188
1296
1260
100
1188
1080
1080
1116
250
672
576
588
612
500
432
504
360
432
Control group
Collect and
Analyze
Data
John examines his
data and
notices that his
control (50g of
sugar) worked
the best in this
experiment, but
not significantly
better than
100g of sugar.
Conclusion
John rejects his
hypothesis, but
decides to revise
his experiment and
re-test using sugar
amounts between
50g and 100g.
43
Experiment
Once again, John
gathers his materials
and carries out his
experiment.
Here are the results.
44
Amount
of
Sugar
(g)
Size of Bread Loaf (cm3)
Trials/Subjects
1
2
3
Average
50
1296
1440
1296
1344
60
1404
1296
1440
1380
70
1638
1638
1560
1612
80
1404
1296
1296
1332
90
1080
1200
972
1084
Conclusion
John finds that 70g of sugar produces the largest loaf.
If the results support the hypothesis, does that mean the hypothesis is
proven true?
If the results do not support the hypothesis-what could be
done next?
What are the final steps to any scientific research/experiment?
Communicate the Results/
Peer Review
John tells his grandmother about his findings and
prepares to present his project in Biology class.
What is evidence? Why is it important?
• A collected body of data from observations and
experiments.
When do scientists become convinced by evidence?
Experiment must be repeated multiple times with
similar results And
repeated by other scientists- with similar results.
Repeatability = Consistent Results = Reliable
Reliability refers to data/results
Validity refers to the design of the experiment
An experiment is usually considered valid if the results
are reliable, but it is not a guarantee.
Laws
• Generalizations of universal relationships related
to the way that some aspect of the natural world
behaves under certain conditions (frequently
expressed as a mathematical equation)
• Can be changed or are abandoned when
contradicted by new experiments.
• Examples:
–
–
–
–
Law of Conservation of Mass
Newton’s Laws of Motion
Bernoulli’s Principle
Newton’s Law of Universal Gravitation
Theories
• A well tested explanation for a broad set of
observations.
• May use models.
• May allow predictions.
• May be changed to explain new observations.
• Examples:
–
–
–
–
–
–
Cell Theory-all living things are made of cells…
Big Bang Theory
Plate Tectonic Theory
Theory of Gravity
Germ Theory of Disease
Theory of Evolution
• How are theories and laws related?
– Theories do not become laws, they explain laws.
(tell how it works and/or what causes it)
How is a theory different from a hypothesis?
Hypothesis
Theory
Educated guess-not tested
Well-tested explanation
Narrow in scope
Broad in scope
Test with controlled experiment
Supported by extensive evidence
If results contradict
If new evidence contradicts
Modify and retest
Verify new evidence/modify theory
New hypotheses
Can lead to
Remember…..
• The body of scientific knowledge changes as
new observations and discoveries are made.
Theories and other explanations change.
New theories emerge and other theories are
modified or discarded. Throughout this
process, theories are formulated and tested
on the basis of evidence, internal
consistency, and their explanatory power.
• Scientific knowledge is both reliable and
tentative (ever-changing).
Models
• Physical, mental, or mathematical representations of how
people understand a process or idea.
–
–
–
–
–
–
–
–
Drawing
Graph
3-D object
Computer program
Mathematical equation
Word description
Analogies (like)
A Game…..
• What makes a model useful?
– Explains all observations (accurately)
– Predictions can be made from the model
– Compatible with other related models
Technology
• Application of scientific understanding for some
specific purpose.
• Examples:
– Radios, televisions and cell phones
» Energy/waves
– Microscopes - light and electron
» Energy/waves and atoms & subatomic particles
– Medical treatments/procedures
» Anatomy/physiology/medicines/etc….
– Genetics - gene therapy, gene identification
» DNA/Chromosomes/Genes/genetic disorders/etc…
Inductive vs. Deductive Reasoning
• INDUCTION
• Specific to General
• Specific observations
lead to general
conclusions
• Conclusions reached are
probable, reasonable,
plausible, and believable;
but are uncertain.
• Observe → pattern →
tentative hypothesis →
conclusion
• Discovery Based Science
• DEDUCTION
• General to Specific
• Generally accepted
premises lead to specific
conclusions
• Conclusions reached are
certain.
• Theory → hypothesis →
observation/data →
confirm/reject
• Hypothesis Based Science
Induction or Deduction???
•
Biff has a tattoo of an anchor on his arm. s
An anchor is used on ships. s
Conclusion: He probably served in the army. g
I
•
All tortoises are vegetarians. g
Bessie is a tortoise. g
Conclusion: Bessie is a vegetarian. s
D
•
A sample of 50 motorists who were stopped by the Police at a seatbelt checkpoint
on a Saturday night at midnight revealed that one in four drivers was either
uninsured, or was not wearing a seatbelt, or both. s Thus, if you get involved in an
accident on the highway, there is a 25% chance the other driver will not be wearing
a seatbelt, or will be uninsured. g
I
•
Discovery Based Science and Hypothesis Based Science differ in that…..