1. Scientific Method/ Background

2. OBJECTIVES:
List and describe/ explain the 5 steps in the scientific method in the correct sequence.
Apply/ use steps in the scientific method in a given problem.
Analyze a scientific problem and be able to identify specific examples of a hypothesis, experiment, data, etc.
Contrast a hypothesis and a theory.
List the 2 functions of a good theory.
Discuss the limitations of science.
Differentiate between a control group from an experimental group and an independent variable from a dependent variable.
Explain the work of Aristotle, Redi, Spallanzani, Needham, and Pasteur concerning the origin of new living organisms--- relate their work to the scientific method.
Compare and contrast 3 kinds of microscopes used in biology--- gives some advantages and disadvantages for each.
Identify and sequence the various levels of organization for the study of life.
Describe common metric units used in science for length, mass, volume, and temperature.

3. Correct observation is most difficult- due to unsuspected bias
Scientific Method
1. Observation
Must be repeatable
Correct observation is most difficult- due to unsuspected bias
People see what they want to see; difficult to explain unconscious prejudice
Several scientists repeating it independently give observation more validity

4. 2. Statement of Problem
To be valuable scientifically, a question must be relevant as well as testable and specific
Proper testing techniques must be available
In general, science does best with “how” or “what” questions
“Why” questions are more difficult/ Ex: “ Why does the universe exist?”  untestable

5. 3. Formulation of Hypothesis
Not a random guess
Hypothesis a tentative answer or postulation based on numerous observations
Scientist does not know if his “guess” was correct or incorrect until he has completed experimentation

6. 4. Experimentation
Provides enough evidence to explain hypothesis
Most difficult step must be a controlled experiment
Requires at least 2 parallel sets of tests, identical in all respects except one
Control Series provides a standard or reference for assessing results of the Experimental Series

7. 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

8. 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
Covered 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.

9. 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)

10. Cont. Scientific Method
5. Formulation of Conclusion: Theory
Based on evidence produce by experimentation
Theory a hypothesis that has withstood repeated testing by many scientists doing independent work
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

11. Microscopes Used in Biology
Light Microscope  tissues, whole cells
2. Transmission Electron Microscope (TEM) slices of cells
3. Scanning Electron Microscope (SEM) surfaces of cells

12. Transmission Electron Microscope

13. SCOPE
ADVANTAGES
DISADVANTAGES
LIGHT
Living cells
Color
Movement
Processes
Low magnification (up to 1000x)
No fine detail
TEM
Very high magnification
Extremely fine details- view internal structures
No living cells
No color
No movement
No processes
Special technique ( fix, slice, stain, freeze, vacuum)
SEM
Surface details
“3D” image/ realistic
Same as TEM (no slicing)

14. Light Microscope
Staph aureus (100x) Onion Cells

15. Transmission Electron Microscope
E. coli
Striated muscle

16. 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)

17. Guess What?!?

18. The dentist drill is covered with tiny diamond chips
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.

19. 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
Covered 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.

20. Spallanzani’s Experiment
Section 1-2
Gravy is boiled.
Flask is
open.
Gravy is teeming
with microorganisms.
Flask is
sealed.
Gravy is free of
microorganisms.
Gravy is boiled.