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 Method1. Observation

a) Must be repeatableb) Correct observation is most difficult- due to unsuspected

biasc) People see what they want to see; difficult to explain

unconscious prejudiced) 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 availablec) In general, science does best with “how” or “what”

questionsd) “Why” questions are more difficult/ Ex: “ Why does the

universe exist?” untestable

Cont. Scientific Method

3. Formulation of Hypothesisa) Not a random guessb) Hypothesis a tentative answer or postulation based on

numerous observationsc) Scientist does not know if his “guess” was correct or

incorrect until he has completed experimentation

4. Experimentationa) Provides enough evidence to explain hypothesisb) Most difficult step must be a controlled experimentc) Requires at least 2 parallel sets of tests, identical in all

respects except oned) 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. Experimentatione) Large samples (#) of organisms must be usedf) Even after careful execution, etc. results may not be

clearg) 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: Theorya) Based on evidence produce by experimentationb) Theory a hypothesis that has withstood repeated testing by

many scientists doing independent workc) 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 observedLaw of Gravitye) Most theories are valid for a time, but with time, exceptions

are foundf) 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 God- leaves anyone free to believe in any God or in none/ many first-

rate 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 Sciencea) 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 cellsColorMovementProcesses

Low magnificationNo fine detail

TEM Very high magnificationExtremely fine details

No living cellsNo colorNo movementNo processesSpecial 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.

OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.

HYPOTHESIS: Flies produce maggots.PROCEDURE

Controlled Variables:jars, type of meat,location, temperature,time

Manipulated Variables:gauze covering thatkeeps flies away from meat

Uncovered jars Covered jars

Several days pass

Maggots appear No maggots appearResponding Variable: whether maggots appear

CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

Section 1-2

REDI’S EXPERIMENT ON SPONTANEOUS GENERATIONRedi’s Experiment on

Spontaneous Generation

Gravy is boiled. Flask isopen.

Gravy is teeming with microorganisms.

Gravy is boiled. Flask issealed.

Gravy is free of microorganisms.

Section 1-2

Spallanzani’s Experiment