Transcript Scientific Method/ Background

Scientific Method/ Background
OBJECTIVES:
1. List and describe/ explain the 5 steps in the scientific method in the
correct sequence.
2. Apply/ use steps in the scientific method in a given problem.
3. Analyze a scientific problem and be able to identify specific
examples of a hypothesis, experiment, data, etc.
4. Contrast a hypothesis and a theory.
5. List the 2 functions of a good theory.
6. Discuss the limitations of science.
7. Contrast “science” vs “non-science”.
8. Differentiate a control group from an experimental group and an
independent variable from a dependent variable.
9. Explain the work of Aristotle, Redi, Spallanzani, Needham, and
Pasteur concerning the origin of new living organisms--- relate their
work to the scientific method.
10.Compare and contrast 3 kinds of microscopes used in biology--gives some advantages and disadvantages for each.
11.Identify and sequence the various levels of organization for the
study of life.
12.Describe common metric units used in science for length, mass,
volume, and temperature.
Scientific Method
1. Observation
a) Must be repeatable
b) Correct observation is most difficult- due to unsuspected
bias
c) People see what they want to see; difficult to explain
unconscious prejudice
d) Several scientists repeating it independently give
observation more validity
2. Statement of Problem
a) To be valuable scientifically, a question must be relevant
as well as testable and specific
b) Proper testing techniques must be available
c) In general, science does best with “how” or “what”
questions
d) “Why” questions are more difficult/ Ex: “ Why does the
universe exist?”  untestable
Cont. Scientific Method
3. Formulation of Hypothesis
a) Not a random guess
b) Hypothesis a tentative answer or postulation based on
numerous observations
c) Scientist does not know if his “guess” was correct or
incorrect until he has completed experimentation
4. Experimentation
a) Provides enough evidence to explain hypothesis
b) Most difficult step must be a controlled experiment
c) Requires at least 2 parallel sets of tests, identical in all
respects except one
d) Control Series provides a standard or reference for
assessing results of the Experimental Series
Cont. Experimentation
Ex: In drug experiments on people, up to 100,000
to 200,000 test, 2 of them controls and 2
experimental groups
Control Series
Experimental Group
a. All conditions same as
Experimental group
a. All conditions same as
Control group
b. No drug taken
b. Drug taken-specific
dose
Cont. Experimentation
e) Large samples (#) of organisms must be used
f) Even after careful execution, etc. results may not be
clear
g) Results of any experiment represents EVIDENCE
the original guess about the answer is confirmed as
correct or incorrect (invalid)
h) If invalid, a new hypothesis and new experiments
must be designed
- Process must be repeated until a hypothesis is
found that can be supported with experimental
evidence
i) Results of experiments cannot be called “proof” or
“fact”, merely evidence for a hypothesis (some
hypothesis have more evidence than others)
Cont. Scientific Method
5. Formulation of Conclusion: Theory
a) Based on evidence produce by experimentation
b) Theory a hypothesis that has withstood repeated testing by
many scientists doing independent work
c) Good theory has predictive value forecasts certain results
based on substantial evidence
- Scientific forecast does not guarantee something will happen- indicates that it is likely to happen with a stated degree of
probability
d) Natural Laws theories that have proved so universally valid
to a high degree of probability
- Ex: Apple falls from tree no exception even observed Law
of Gravity
e) Most theories are valid for a time, but with time, exceptions
are found
f)
Science is a steady progression, not revolution
- Ex: Isolation and synthesis of a gene took 5 years
Limitations of Science
1. Science is confined to use of the Scientific Method-this is the beginning and end of science.
2.
Anything to which the scientific method can be applied
now or in the future. Anything to which this method
cannot be applied is NOT science.
Cont. Limitations of Science
3. Does the idea of God lend itself to scientific study?
a) Test hypothesis: God is universal and exists everywhere and in
everything
b) An experiment about God would require 2 situations: one w/ God,
one without, but otherwise identical
c) If hypothesis is correct: God would exist everywhere-- be present in
every test and could never devise a situation in which God is NOT
present
d) If hypothesis is wrong: God would not exist-- would be absent from
any test and could never devise a situation in which God is present
e) Hypothesis is untestable-- cannot run controlled experiment
f) Concept of God falls out of scientific domain
g) Are scientists godless? Science does not prove nor disprove Godleaves anyone free to believe in any God or in none/ many firstrate scientists are priests, many are agnostics
Cont. Limitations of Science
4. The aim and purpose of science is to make and
use theories. Science finds evidence for
theories-- does not deal with truth or proof.
5. Science does not make value judgments or
moral decisions. Scientific results do not contain
built-in values.
6. Science cannot determine whether or not one
should have moral standards or which set one
should live by.
Cont. Limitations of Science
7. Forms of Science
a) Basic Research (Pure Science)
• Done to further understand nature
• Practical applications are disregarded
• Publish papers, experiments, research
b) Applied Science (Practical Science)
• Applies the results of pure science to practical
uses
• Doctors, engineers, criminologists, physical
therapists, etc.
• Technology
Microscopes Used in Biology
1. Light Microscope  tissues, whole cells
2. Transmission Electron Microscope (TEM)
slices of cells
3. Scanning Electron Microscope (SEM)
surfaces of cells
SCOPE
ADVANTAGES
DISADVANTAGES
LIGHT
Living cells
Color
Movement
Processes
Low magnification
No fine detail
TEM
Very high magnification No living cells
Extremely fine details
No color
No movement
No processes
Special technique ( fix,
slice, stain, freeze,
vacuum)
SEM
Surface details
“3D” image
Same as TEM (no
slicing)
Light Microscope
Staph aureus (100x)
Onion Cells
Transmission Electron Microscope
E. coli
Striated muscle
Scanning Electron Microscope
Mascara brush covered w/ dried mascara
& flakes of skin
Cat flea flattened from side to side
along with the spines on its head
(have either simple eyes or no eyes
at all)
Guess What?!?
The dentist drill is covered with tiny diamond
chips. Diamonds are the hardest substance
known and will easily wear away tooth
particles as the drill spins at high speeds.
Redi’s Experiment on
Spontaneous Generation
REDI’S EXPERIMENT ON SPONTANEOUS
GENERATION
Section 1-2
OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.
HYPOTHESIS: Flies produce maggots.
PROCEDURE
Uncovered jars
Controlled Variables:
jars, type of meat,
location, temperature,
time
Covered jars
Several
days pass
Manipulated Variables:
gauze covering that
keeps flies away from
meat
Responding Variable:
whether maggots
Maggots appear
No maggots appear
appear
CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous
generation of maggots did not occur.
Spallanzani’s Experiment
Section 1-2
Gravy is boiled.
Flask is
open.
Gravy is teeming
with microorganisms.
Gravy is boiled.
Flask is
sealed.
Gravy is free of
microorganisms.