Transcript Unit 1 - Introduction & Scientific Method

Get Ready for A & P!
The Scientific Method
Biology
 Scientific
study of life
 Lays
the foundation for asking basic
questions about life and the natural world
 Anatomy
biology
& Physiology is one branch of
Why Study Biology?
 To
learn how organisms are constructed,
how they function, where they live, and
what they do
 To
help develop, modify, and refine ideas
about life
How do we study Biology?
 Biology
is studied using the scientific
method
 Different
than other modes of study
because it has specific steps and rules
What is the Scientific Method?

Observe phenomenon

Develop hypotheses

Make predictions

Devise test of predictions

Carry out test and analyze results

Publish results so others can repeat
Inductive Logic
 Using
observations and facts to arrive at
generalizations or hypotheses - begins the
scientific method
 Observation:
Eagles, swallows, and robins
have feathers
 Hypothesis:
All birds have feathers
Deductive Logic
 Drawing
a specific conclusion based on a
generalization - after testing a hypothesis

Generalization - Birds have feathers

Example - Eagles are birds

Conclusion - Eagles have feathers
Role of Experiments
 Used
to study a phenomenon under
known conditions
 Allows
you to predict what will happen if a
hypothesis is supported
 Can
never prove a hypothesis 100%
correct
Experimental Design
 Control


group
A standard for comparison
Identical to experimental group except for
variable being studied
 Sampling
error

Nonrepresentative sample skews results

Minimize by using large samples
Biological Therapy Experiments
Can we use viruses that attack bacteria
(bacteriophages) to fight infections?
Experiment 1
 Hypothesis
- Bacteriophages can protect
mice against infectious bacteria
 Prediction
- Mice injected with
bacteriophages will not die as a result of
bacterial injection
Experiment 1 - Test
•
Experimental group
•
Inject with bacteria and
bacteriophage
Control group
Inject with bacteria and saline
Experiment 1 Results & Conclusion
 Experimental
group
All mice lived
 Control
group
All mice died
 Conclusion
- Bacteriophage injections
protect mice against bacterial infections
Experiment 2
 Prediction
- Bacteriophage injections will
be a more effective treatment than a
single dose of the antibiotic streptomycin
 Test
- Mice injected with bacteria, then
with saline, streptomycin, or bacteriophage
Experiment 2 - Results


With 2nd injection:

Bacteriophage - 11 of 12 mice lived

60 mg/gm streptomycin - 5 of 12 lived

100 mg/gm streptomycin - 3 of 12 lived

Saline - all mice died
Conclusion - Bacteriophage treatment can be as
good or better than antibiotic treatment
Minimizing Variables
 All
mice were same age and sex, reared
under same conditions
 Each mouse in each test group received
exact same treatment
 All mice in control group received same
amount of saline
 Variable tested was antibiotic treatment
versus bacteriophage treatment
p.12
Hypothesis
Olestra® causes intestinal cramps.
Prediction
People who eat potato chips made with Olestra will be more
likely to get intestinal cramps than those who eat potato
chips made without Olestra
Experiment
Control Group:
Eats regular
potato chips
Experimental Group:
Eats Olestra
potato chips
Results
Control Group:
Some get
intestinal
cramps
Experimental Group:
Some get intestinal
cramps
Conclusion
Percentages are about equal. People who eat potato chips
made with Olestra are just as likely to get intestinal cramps
as those who eat potato chips made without Olestra.
These results do not support the hypothesis.
Fig. 1-10, p.12
Scientific Theory
A
hypothesis that has been tested for its
predictive power many times and has not
yet been found incorrect
 Has


wide-ranging explanatory power
Darwin’s theory of evolution by natural
selection
The Cell theory - all living things are made of
cells
Scientists Raise Questions
The external world, not internal conviction,
must be the testing ground for scientific
beliefs
Limits of Science
 Scientific
approach cannot provide
answers to subjective questions
 Cannot provide moral, aesthetic, or
philosophical standards
 Conflict with supernatural beliefs


Copernicus
Darwin