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Introduction & Scientific Method
Biology 101A
Spring 2008
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Introduction
Safety
Notebooks
Scientific method
Protocol writing experiment
Review protocol experiment
Preview Tuesday’s lab
Safety- Appendix A
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Fire and earthquake
Eye protection
No food or drinks
Wash your hands when leaving
Dispose of hazardous/biohazardous materials
appropriately
How to be successful in Bio 101A
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Come to class
Be prepared
Be punctual
Complete all assignments in a timely manner
Reflect on your learning
Apply lecture concepts to lab (and vice versa)
Get help, help others (cooperate)
Notebooks
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Hardbound
Name edges & cover; number pages
Pages 1-4: TOC
Blue or black ink
No wite-out
Completely chronological order
Date & 2 signatures for each page- before
leaving lab
Scientific Method
• Not formulaic
• Inquiry based
• Discovery Science vs. Hypothesis testing
Charles Darwin became curious about how
species came about
• Dropped out of med
school
• Didn’t much like
Divinity school, either
• Became a naturalist
aboard the HMS Beagle
The Voyage of the Beagle
Darwin’s critical observations were
comparisons between island species and
mainland species
Marine Iguana and South American Iguana
Flightless cormorants live only on the
Galapagos
A Variety of Finches are found in the
Galapagos
Finches each have
adaptations for
different small
island
environments
Darwin’s inference: The finches have a
common ancestor, which adapted to different
niches
Likewise, the marine iguanas must have
come from the mainland
Hypothesis testing
LE 1-25a
Observations
Question
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
LE 1-25b
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
Test prediction
Test prediction
Test falsifies hypothesis
Test does not falsify hypothesis
Does excess iron decrease growth
in laboratory rats?
• How can we test this?
• How many groups should we
use?
• What size are the groups?
• How shall we create the
groups?
• What is our independent
variable?
• What is our dependent
variable?
• What are the control variables?
Is evolution testable?
Adaptive radiation in the lab
• In variable environments,
varying strains of P.
fluorescens are generated
• Strains are genetically
distinct
• When environments are
homogeneous, no such
variants are generated
ANALYSIS OF
eyeless FUNCTION
eyeless (ey)
ey2 and eyR = spontaneous mutations
mutant phenotype = small/no eyes
recessive to wild-type allele
Halder et al.
eyeless
NECESSARY?
SUFFICIENT?
Knock the gene out
LOSS-OF-FUNCTION
Ectopically express gene
GAIN-OF-FUNCTION
NO
Expression
of phenotype
NECESSARY!
Expression
of phenotype
NO
Expression
of phenotype
Not
Necessary
Not
Sufficient
Expression
of phenotype
SUFFICIENT!
A Closer Look at Hypotheses in Scientific
Inquiry
• A scientific hypothesis must have two important
qualities:
– It must be testable
– It must be falsifiable
The Myth of the Scientific Method
• The scientific method is an idealized process of inquiry
• Very few scientific inquiries adhere rigidly to the
“textbook” scientific method
A Case Study in Scientific Inquiry: Investigating Mimicry in Snake
Populations
• In mimicry, a harmless species resembles a harmful
species
• An example of Batesian mimicry is a stinging honeybee
and a nonstinging mimic, a flower fly
LE 1-26
Flower fly (nonstinging)
Honeybee (stinging)
LE 1-27
Scarlet king snake
Key
Range of scarlet
king snake
Range of eastern
coral snake
Eastern coral
snake
North
Carolina
South
Carolina
Scarlet king snake
LE 1-28
(a) Artificial king snake
(b) Artificial brown snake that has been attacked
LE 1-29
17%
In areas where coral snakes
were absent, most attacks
were on artificial king snakes.
83%
Key
North
Carolina
% of attacks on
artificial king snakes
% of attacks on
brown artificial snakes
Field site with
artificial snakes
South
Carolina
16%
84%
In areas where coral
snakes were present,
most attacks were on
brown artificial snakes.
Designing Controlled Experiments
• What variables were
controlled in this
experiment? How were
they controlled?
• Researchers usually
“control” unwanted
variables by using
control groups to cancel
their effects
An alternative experimental
design